Department of Agriculture Ministry of Agriculture and Forest The Kingdom of Bhutan

THE PREPARATORY SURVEY REPORT

ON

THE PROJECT FOR IMPROVEMENT OF

TAKLAI IRRIGATION SYSTEM IN

SARPANG DISTRICT

IN

THE KINGDOM OF BHUTAN

November 2012

JAPAN INTERNATIONAL COOPERATION AGENCY

SANYU CONSULTANTS INC

RD

JR

12-093

No.

PREFACE

Japan International Cooperation Agency (JICA) decided to conduct “The

Preparatory Survey on the Project for Improvement of Taklai Irrigation System in

Sarpang District in the Kingdom of Bhutan” and entrust the survey to Sanyu

Consultants Inc.

The survey team held a series of discussions with the officials concerned of the

government of the Kingdom of Bhutan, and conducted a field investigation. As a

result of further studies in Japan, the present report was finalized.

I hope that this report will contribute to the promotion of the project and to the

enhancement of friendly relations between our two countries.

Finally, I wish to express my sincere appreciation to the officials concerned of the

Government of the Kingdom of Bhutan for their close cooperation extended to the

survey team.

November, 2012

Teruyoshi KUMASHIRO

Director General,

Rural Development Department

Japan International Cooperation Agency

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Summary

1. Introduction

Agricultural sector in Kingdom of Bhutan is the key industry which employs 69% of Bhutan’s population and occupies 14% of GDP. It has a substantial share of the country’s rural poor population, so that poverty reduction is placed as the top priority in the National Development Plan. However, Bhutan is totally a mountainous country. Agricultural land occupies only 7.7 % of the country’s land. Furthermore, each agricultural land holding area and each farm plot of farmers are limited to small size, due to terrace farming in the steep topography.

The Gross National Happiness Commission (GNHC) formulated the 10th five year national development plan in 2009, which is currently being used as guide. The target of the national plan was to secure the stable and robust macroeconomic framework by central policy of social development and poverty alleviation. In addition, it aims at self-reliant finance, good accounting balance, restraining of inflation and soundness of foreign debt, which are controlled by efficient public investment.

In the mid-term review of the 10th five year plan conducted, it was mentioned in report, that rice self-sufficiency is expected to improve by 55% until 2013 which is end of year the plan.

The 11th five year plan is now being drafted. The GNHC prepared a guideline that sets the overall goal as “Self-Reliance and Inclusive Green Socio-Economic Development”.

In regard to the entire economic status in Bhutan, the acquisition of foreign currency is generated by the tourism industry. The other source of revenue is from the development of hydraulic power generation (financed by the Indian Government) getting profit from selling electric power. Therefore average economic growth rate increased from 9% in 2002 to 2008 to 11.8% in 2010. The Gross National Income (GNI) per person in Bhutan is US$ 2,070 (sourced from World Bank 2011). The Gross Domestic Product (GDP) of structural rate for each category in 2010 is electric power sector: 17.6%, agriculture and forest: 16.8%, construction: 8.7%, industry: 2.2%, service business: 36.5%.

2. Back ground of the project

Taklai Irrigation Scheme, the largest irrigation system in Bhutan located in Sarpang district is considered as the key irrigation system serving for the important production area in the south part of the country. This irrigation system was completed in the 1980’s with having due support by United Nations World Food Program (WFP), United Nations Development Program (UNDP) and others. The system was planned aiming at double cropping of rice, as of construction completion ,for the 1,300 Ha beneficiary areas for 756 farm households, whereas, 883 Ha beneficiary areas for approx. 530 farm households as of 2011. Largely, the system can be divided into two (2) parts, one served by high level canal and the other by low level canal. It is expected that attaining enlarged rice cropping in dry season through restoring the subject irrigation system function will greatly contribute to raising up of self-sufficiency ratio of rice at the national level and also to improvement of agricultural productivity in Sarpang district.

However, those existing intake facilities and main canals of the system have been suffering from flood damages almost every year, due to its being located near the Taklai River, which changed its river water route so often. Furthermore, it is noteworthy to mention, that the repair cost for the incurred damages is considered a big burden to the responsible agency. Also, repair works remain at provisional level only. Considering the present situation, it would seem to be difficult to consider a

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stable and quantitatively adequate irrigation water supply. In addition, the flood that occurred in September 2010 heavily damaged the existing intake facilities and main canal to an extent never experienced before. For the said damages, the government is trying to implement emergency rehabilitation works partly on the system. However, there is a need to urgently undertake comprehensive rehabilitation works for the intake facilities in a sustainable manner for higher durability of the system.

3. Outline of the project and study

The purpose of the project study is to improve and restore the functionality of Taklai irrigation system, the largest irrigation are in Bhutan, and contribute in the increase in rice self-sufficiency and expansion of agricultural productivity in the area.

And the project is formed by discussion with Bhutanese based on the request letter from Bhutanese and result of site survey, in addition, the planned project components are same as written items in request letter, there is no any additional or cancel items. Site survey schedule were as follow;

The first site survey : Middle of January 2012~ Middle of February 2012 (31 days)

The second site survey : Middle of September 2012~ End of September 2012 (10 days)

Table：Outline of the project components Item of facility Description

1. Integrated headwork ･Fixed Weir：L 38.9m x 1.0m ･Bed protection：L= 30.0m

2. Head race and sedimentation basin

･Box culvert：L= 358.9m ･Open canal：L= 631.2m ･Sedimentation Basin：L= 37.5m ･Retaining wall：H 3.9m x L 410m

3. Link canal ･Rise up wall：L= 654.6m ･Improvement：L= 109.6m

4. Confluence between Link canal and Low level intake

･L type retaining wall H 2m x L 4.65m ･Newly constructing gate：One (1) gate

5. High Level canal

･Wet masonry：L= 123.7m ･Rise up wall：L=165m ･Covered by concrete：L= 205.8m ･Rehabilitation of leakage at 2nd siphon outlet：Covered by concrete･Rehabilitation of leakage at aqueduct：L=50m ･Safe fence around siphon：6 nos. ･Improvement of siphon：covered by reinforce concrete ･Concrete bridge：re-construction (width 4m) x 2 bridges

6. Exposed siphon pipe on High Level Canal ･Protection of exposed siphon pipe at 3rd siphon L= 45m

7. Gate on High and Low Level Canal ･High Level Canal : Check and distribution gate：10gates ･Low Level Canal : Check gate：2gates

8. Water gauge at integrated headwork ･Water gauge：Sound wave type 1 set

9. Protection dike at downstream of Taklai River

･Dike：W 4.0m x H3.0m x L 340m ･Retaining wall：H 3.9m x L 340m

10. Soft component ･ Instruction and assistance for operation of facility, water management, maintenance

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(1) Overall goal and project purpose

As a overall goal of this project, National Development Tenth Five-Year Plan (2008-2013) is a guiding

plan of Bhutan related to this Project. From agricultural point of view, Ministry of Agriculture and

Forests (MoAF) has provided strategic programs for strengthening markets, marketing and production

of agricultural products for the purpose of ensuring food security and alleviating rural poverty.

Concretely, 29 programs have been implemented through the initiative and in charge of MoAF, by

which the following impacts are expected in terms of agriculture:

① Improving self-sufficiency ratio of rice from 50% to 59%,

② Increasing the level of annual farm-income from Nu10,700 to Nu35,000 and

③ Reducing the rate of local population stratum below poverty line from 30.9% to 20%.

“Contribution to the realization of double-cropping of rice in the target beneficiary area” is considered

as the overall goal of this Project. Also, as regards the Project purpose, it aims at “enabling to

supply irrigation water to the initially targeted area planned in Taklai Irrigation System”.

This system has the largest beneficiary area in irrigation projects in Bhutan (over 1,000 ha) and the only one nationally-managed project. This Project is expected to serve as a model scheme in Bhutan because synergetic effect can be realized between this Project and nationally implemented canal rehabilitation scheme by the reason that rehabilitation of existing canals has been implemented as a national strategy with the objective of expanding the scale of dry-season irrigation, thus enabling stable water supply throughout the year, thereby targeting to mitigate poverty rate and to promote higher farm income, also by the reason that larger scale of project output can be anticipated by its large impact since it has larger project area than the scale of perimeter in other district (about 200ha).

In order to fulfill the above-mentioned overall goal and the project purpose, it is indispensable to realize stable water intake and water supply with permanently functioning facilities in which climatic change (abnormal scale of flood etc) are taken into consideration in its design, and it is also essential to combine new-construction and rehabilitation of irrigation facilities by hard component with the capacity improvement of maintaining and managing them by soft component.

(2) Basic policy

In formulating the Project, the position, the effects, technical and economic feasibility/ relevance of Japanese Grant Aid toward the implementation of this Project are to be verified, thereby essential and optimum design of the planned facilities is provided for obtaining proper fruit/ outputs of the Project.

Basic principles applied to the facility design include integrating the existing water-intake system of diverting water at two intakes at upstream (High Level Canal : H.L.C) and downstream (Low Level Canal : L.L.C) sites into an integrated head works, satisfying the capacity of the facility to convey planned water quantity by this integration, also repairing/ rehabilitating facilities of the existing irrigation system the irrigation functions of which have been damaged and deteriorated/ dilapidated.

To provide the structure of the integrated head works with sufficient strength that will be constructed at the upstream of the existing H.L.C intake with stabilized river-bed and that allows to take the totaled water quantity of both existing H.L.C and L.L.C sites. Irrigation water thus taken into the canal will be distributed at its existing downstream diversion points according to the water requirement for each

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irrigation area. The stable supply of irrigation water is pursued by estimating irrigation water requirement and flood discharges to be planned in the Project and strengthening a part of head race by newly constructing culvert structure with reinforced concrete that will be connected to the existing main canal at H.L.C site.

(3) Policies applied to natural/ environmental conditions

･ Flood discharge

1,710m3/s is adopted as the design discharge that has been calculated from 1/50 year’s probable

rainfall which based on the record at Bhur Observatory Station. In this regard, this value is larger than

the maximum recorded flood discharge in the past estimated from the observed flood vestiges.

･ Drought discharge

Annually probable discharge at the site of the planned head works is estimated at around 1.12m3/s

from the observation result available in and around the site. Since this value is evidently lower than

design irrigation water requirement, 2.24m3/s as shown below, it is considered possible that in the

course of probability evaluation drought discharge corresponded to 50% of the design water

requirement appear every year.

Yet, a discharge of about 3.8m3/s has been observed at the planned site of the head works during the

study team was in February, or during dry season, and the interviewed persons in this study told that

such a level of discharge as observed during the study was seen every year in the interview survey.

Considering these situations, each facility is designed based on 2.24m3/s, required irrigation water

quantity, however, taking account of some possibility of evolving water-deficit years failing to satisfy

the planned water supply, such practices as rotational irrigation and time-limited irrigation covering all

blocks in a day is planned to cope with such possibility.

･ Geology at the planned site of head works

Geological formation in and around the planned site of head works can roughly be classified into gravel and pebbles over the stream-bed and quartzite / gneissic boulder derived from volcanic origin materials judging from the result of a geologic survey. Both of these strata are relatively compact judging from the measurement results with 35° or larger for their internal friction angle and about 2.0tf/m3 as unit weight.

Therefore an apron of head works is designed as floating type because the foundation is conceived high permeable strata.

(4) Farming and irrigational (on-farm) conditions

As this Project has main objective of functional recovery for Taklai Irrigation System through new construction of integrated head works and head race as well as rehabilitation of main canal and appurtenant structures etc, farming environment of the beneficial farmers will be improved as a result of enabling stable supply of irrigation water.

As far as crop selection has basically been kept at farmer’s own disposal without any policy intervention, it is predicted that some farmers surely try to be engaged in spring crops (dry-season

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cropping) with paddy and wheat once stable supply of irrigation water is realized.

No radical change is brought in the operation and maintenance of terminal irrigation facilities and sharing system of water management (operation of water-gates).

(5) Policies applied to socio-economic situations

It is considered that the rehabilitation of Taklai Irrigation System and subsequent improvement in farming conditions contribute to beneficiary farmer’s increased food production and their livelihood improvement, leading to favorable impact to local economy. In so far as this Project has the objective of rehabilitating the existing Taklai Irrigation System, it won’t bring any new large-scaled development in the area. It follows that living customs and traditions of the beneficiaries will be conserved as they are now.

Further, from gender point of view, men and women used to share farm labor/ practices within household or community, hence it is considered that expansion of cropping area would not result in an increased burden for women only.

(6) Policies towards management and operation/ maintenance

A soft component is provided for realizing of following capacity improvement targets as a supporting

activity, thus assisting to obtain required knowledge and techniques and to sustain operation and

maintenance.

・Because no permanent facility exists that doesn’t need any maintenance / management, operation

and maintenance techniques should be mastered with the preventive and conservative ideas in

order to keep as long life as possible of the facilities that are newly constructed or rehabilitated by

this Project,

・Pertinent method of water management (operation of gates) should be trained in order to make

improved capacity of the facilities fully functioning.

(7) Policies on the establishment of the grade of the planned facilities

The facilities of Taklai Irrigation System shall be designed by adopting the following parameters,

based on natural and environmental conditions and the planned scale of the target area:

・Design water intake: 2.24 m3/s （maximum intake quantity）

・Design flood discharge: 1,710 m3/s（probable flood discharge of once in 50 years; 1/50）

Based on the Taklai river that facilities should be planned under hard natural conditions as observed in

this case, it is considered relevant from the economic point of view to allow some degree of possible

damages to such extent that it will not reach to a serious damage by mitigating the natural action,

rather than directly resisting against evolving natural forces, What is important is the establishment of

proper and regular maintenance to sustain the project facilities over a long period of time instead of

providing excessive or large- scale of facilities.

For the facilities to be constructed outside of the river such as canal, the same policy is applied to

repair and rehabilitation works, considering that the possibility of proper maintenance by Bhutanese

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can lead to long-term operation of functions of the facilities

4. Project implementation schedule and estimation of project cost

The project implementation schedule is shown as below;

･Detailed design : approx. four (4) months ･Bidding and contract for construction : approx. two and half (2.5) months ･Construction works : approx. 21months

The project cost to be borne by the Bhutanese side is estimated to be about 9 million JPY.

5. Project evaluation

(1) Relevance

The number of beneficiaries is approximately 4,300 while household is 530. The farmer's income in this area is approximately US$ 390 (17,700 Nu ) per household. While GNI (Gross National Income) is US$ 2,070 per person in Bhutan, is means that the target area’s income is approximately one-fifth of national level. The farmers account for the majority of population in the area, therefore almost people are considered at the lower level than national level in Bhutan. Accordingly, the number of poor is higher in this area.

In the 10th five-year national development plan for Bhutan, the target was to reduce the ratio of poverty from 23.2 % (2007) to 15%. In addition, as there are many poor people in the rural area, rural integrated development is categorized as one of the important area for development. In addition, increase in self-sufficiency of crops is an urgent issue due to the geological condition in Bhutan therefore the aim is to increase self-sufficiency from 50% of the current rate to 59 % until 2018.

The largest irrigation system in Sarpang District in Bhutan, the Taklai irrigation system, considered as the productive crucial are in south Bhutan, is expected to contribute to the improvement of national self -sufficient of rice and agricultural production in this area with the expansion of cropped area in dry season by restraining of irrigation system facility.

The 11th five-year national development plan also plans in preparation to improve agricultural infrastructure, expansion of the irrigation area and increase farmer's income, hence the implementation of this project is expected to become a model project on agricultural development in Bhutan.

A mutual concern between Bhutan and Japan, since the establishment of diplomatic relations on 28th March in 1986, is to have structured friendly relations through the exchanges between imperial and royal family and economic support such as instruction of agriculture promotion. Therefore Japan is considered as country that can provide ODA support and assistance to Bhutan, while Bhutan is considered as the important for Japan as it provides support and espousal on election or resolution at international agency to Japan.

The major emphasis for Bhutan based on Japanese policies are as follows; ① Agricultural and rural development (mechanization of agriculture, improvement of agricultural infrastructure ), ②Improvement of economic foundation (road networks, electrification of rural area, diffusion of information ), ③Social development (strengthening of the educational service, strengthening of

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medical and health services, development of human resources for the job creation), ④ Good governance (decentralization). In this project, ① Agricultural and rural development (mechanization of agriculture, improvement of agricultural infrastructure) are included as part of the project therefore the project conforms to policy of Japan.

In addition, according to the achievement of Millennium Development Goals (MDGs) of United Nations (UN), support to “Human security" is a crucial policy that is being promoted. The project also promotes the development and improvement of agricultural productivity to increase crop self-sufficiency The Project therefore contribute to the policy " Eradicate Extreme Poverty & Hunger" which is one of the development policy on MDGs,

Bhutan advocates Gross National Happiness (GNH) as the central priority for the national plan, which does not pursue the physical or economic improvement but spiritual improvement.. This idea is focused as though it would overcome a deadlock and cooped-up feeling of the society which has given priority to development of economical efficiency, and the examination in order to introduce the idea of GNH into a new indicator for MDGs is beginning at UN, now. Accordingly, to contribute the national policy based on GNH in Bhutan expects to contribute the achievement of MDGs

(2) Effectiveness

The expected impact of the implementation of the project is as follows;

･ Quantitative effects Table: Indicator for the Quantitative effects

Items Base year（2012） Target year（2018） Remarks Irrigation water supply in dry season

0 m3/s max. 2.24 m3/s *1) enable to supply irrigation water by construction of head works

Irrigation area 883 ha max. 1,120 ha*2) enable to supply irrigation water by rehabilitation of damaged siphon

Paddy area in dry season

10 ha 560 ha

expand the double crop area by supplied stable water in dry season. as the condition of assumptions, the cropping pattern of irrigation area in dry season is divided to vegetable and rice by a half respectively.

Annual maintenance cost

ave.3,500,000 Nu 1,750,000 Nu alleviation of rehabilitation works for the headrace canal and protection wall by gabions

※Target year is three years later after the construction

*1) Maximum planned irrigation water is considered of probability that drought discharge of Taklai river by

examined probable rainfall might be lower than planned irrigation water, 2.24 m3/s.

*2) Actual registered house hold and beneficiaries is approximately 530 and 4,300 respectively. Those are

expected to receive the benefit directly.

･ Qualitative effects

① The farmer's income will increase with the increase in rice production and better selling price.

② With the inclusion of soft component activity, there will be improvement of O &M skills and techniques. Also, collection of data and sharing of information will contribute to keep the good condition of the irrigation facility.

③ O & M activities in Taklai irrigation system will be good model and extended to other similar

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area.

④ through extension of rice double crop, the operating rate of machine for agricultural works which is not used during fallow periods will increase.

⑤ The direct effect of disaster prevention for irrigation area or facility will be expected by construction of river dike; in addition, reinforcement of existing protection wall and new construction of intake or delivery canal with good durability will bring the stabilization of irrigation facility on flood period and, accordingly, contribute to raising up rice production and farmer's income.

CONTENTS

Preface

Summary

Contents

Location Map / Perspective

List of Figures & Tables

Abbreviations

Units

Chapter 1 BACKGROUND OF THE PROJECT........................................................ 1-1

1-1 Introduction ................................................................................................................... 1-1

1-2 Outline of the preparatory survey ................................................................................... 1-1

1-3 Agriculture...................................................................................................................... 1-2

1-3-1 Land Ownership .................................................................................................... 1-2

1-3-2 Crops ..................................................................................................................... 1-3

1-3-3 Rice Production ..................................................................................................... 1-3

1-3-4 Utilization of Agricultural Machinery and Animal Draft Power........................... 1-4

1-3-5 Role of Female and Male on Rice Production and Work Sharing ........................ 1-5

1-3-6 Marketing .............................................................................................................. 1-5

1-3-7 Agricultural Extension........................................................................................... 1-6

1-3-8 Agricultural Associations and Cooperatives ......................................................... 1-7

1-4 Natural condition .......................................................................................................... 1-8

1-4-1 Topographic, Geological and Climatic classification ............................................ 1-8

1-4-2 Meteorological condition at Taklai Irrigation Area ............................................... 1-8

1-4-3 Hydrological condition at the site of head works .................................................. 1-11

1-4-4 Effects of earthquake ............................................................................................. 1-14

1-4-5 Geological survey .................................................................................................. 1-14

1-4-6 Topographic survey ............................................................................................... 1-15

1-5 Environmental and Social Consideration ...................................................................... 1-15

1-5-1 Preparation and submission of IEE Report.............................................................. 1-15

1-5-2 Procedure for securing environmental approval .................................................... 1-15

1-5-3 Environmental Impact Assessment ....................................................................... 1-15

1-5-4 Elaboration of impact-mitigating measures ........................................................... 1-24

1-5-5 Monitoring Plan and Environmental Checklist ..................................................... 1-25

1-5-6 Stakeholder’s Meeting ........................................................................................... 1-26

1-5-7 Land acquisition and resettlement ......................................................................... 1-26

1-5-7-1 Necessity of land acquisition and resettlement ................................................ 1-26

1-5-7-2 Legal framework for land acquisition and resettlement ................................... 1-26

1-5-7-3 The range of area for land acquisition and resettlement .................................. 1-26

1-5-7-4 The detailed measurement for compensation and support ............................... 1-26

1-5-7-5 The way of complaint management ................................................................. 1-26

1-5-7-6 Implementation agency for the resettlement and responsibility ....................... 1-26

1-5-7-7 Implementation schedule .................................................................................. 1-26

1-5-7-8 Finance and budget .......................................................................................... 1-26

1-5-7-9 Monitoring and monitoring form by executive agency .................................... 1-26

1-5-7-10 Meeting of residence ........................................................................................ 1-26

1-5-8 Draft monitoring form ........................................................................................... 1-26

1-5-9 Check list of environment ..................................................................................... 1-26

Chapter 2 CONTENTS OF THE PROJECT................................................................ 2-1

2-1 Basic Concept of the Project........................................................................................... 2-1

2-2 Outline design of the requested Japanese assistance ...................................................... 2-2

2-2-1 Design Policy .............................................................................................................. 2-2

2-2-1-1 Basic policy.......................................................................................................... 2-2

2-2-1-2 Policies applied to natural/ environmental conditions ......................................... 2-4

2-2-1-3 Farming and irrigational (on-farm) conditions..................................................... 2-5

2-2-1-4 Policies applied to socio-economic situations...................................................... 2-5

2-2-1-5 Policies on the situations of construction / procurement...................................... 2-6

2-2-1-6 Policies on the utilization of local constructors (construction firms)................... 2-6

2-2-1-7 Policies towards management and operation/ maintenance ................................. 2-6

2-2-1-8 Policies on the establishment of the grade of the planned facilities..................... 2-7

2-2-1-9 Policies concerning work method/procurement method and construction period ..... 2-7

2-2-2 Basic plan (Construction plan/Equipment plan).......................................................... 2-8

2-2-2-1 Design irrigation water requirement .................................................................... 2-8

2-2-2-2 Design of the integrated head works .................................................................... 2-10

2-2-2-3 Design of head race.............................................................................................. 2-34

2-2-2-4 Reinforcement of the existing gabion wall .......................................................... 2-42

2-2-2-5 Protection dike at the downstream of Taklai River.............................................. 2-46

2-2-2-6 Existing main canal and related facilities............................................................. 2-48

2-2-3 Outline design drawing................................................................................................ 2-51

2-2-4 Implementation Plan.................................................................................................... 2-92

2-2-4-1 Implementation policy ......................................................................................... 2-92

2-2-4-2 Implementation conditions................................................................................... 2-94

2-2-4-3 Scope of works..................................................................................................... 2-96

2-2-4-4 Consultant supervision ......................................................................................... 2-97

2-2-4-5 Quality control plan.............................................................................................. 2-99

2-2-4-6 Procurement plan ................................................................................................. 2-99

2-2-4-7 Operational guidance plan.................................................................................... 2-101

2-2-4-8 Soft component (technical assistance) plan......................................................... 2-101

2-2-4-9 Implementation schedule..................................................................................... 2-104

2-3 Obligation of the government of Bhutan ....................................................................... 2-106

2-3-1 Items to be borne by the Bhutanese side on construction division/procurement division 2-106

2-3-2 Items to be borne by the Bhutanese side on the software component plan ................ 2-107

2-3-3 Environmental and social evaluation.......................................................................... 2-107

2-3-3-1 Current situation of procedure to obtain environmental permit for this Project.. 2-107

2-4 Project operation and maintenance plan ........................................................................ 2-107

2-4-1 Project management/ operation and maintenance system .......................................... 2-107

2-4-2 Operation/ Maintenance and Management Plan ......................................................... 2-108

2-5 Estimated project cost .................................................................................................... 2-109

2-5-1 Estimated cost for the project ..................................................................................... 2-109

2-5-1-1 Project cost borne by the Bhutanese side ............................................................ 2-110

2-5-1-2 Cost estimating assumption................................................................................. 2-110

2-5-2 Management, operation and maintenance cost ........................................................... 2-110

Chapter 3 PROJECT EVALUATION........................................................................... 3-1

3-1 Precondition ................................................................................................................... 3-1

3-2 Necessary inputs by the government of Bhutan............................................................. 3-1

3-3 Important assumption..................................................................................................... 3-1

3-4 Project evaluation........................................................................................................... 3-2

3-4-1 Relevance.................................................................................................................... 3-2

3-4-2 Effectiveness............................................................................................................... 3-3

[Appendices]

Appendix-1．Member List of the Study Team............................................................................. A1-1

Appendix-2．Study Schedule....................................................................................................... A2-1

Appendix-3．List of Parties Concerned in the Recipient Country............................................... A3-1

Appendix-4．Minutes of Discussion（M/ D） ........................................................................... A4-1

Appendix-4.1 M/ D on 25th January 2012 .............................................................................. A4-1

Appendix-4.2 M/ D on 19th September 2012 ......................................................................... A4-15

Appendix-5．Soft Component (Technical Assistance) Plan ........................................................ A5-1

Appendix-6．References .............................................................................................................. A6-1

Appendix-6.1 Map of Beneficiary Area................................................................................. A6-1

Appendix-6.2 Calculation of the bar screen on Head works.................................................. A6-2

Appendix-6.3 Calculation of design flood discharge and drought water discharge............... A6-3

Appendix-6.4 A study for the result of Taklai River discharge measurement ....................... A6-9

Appendix-6.5 Summary of WUA workshop on the Taklai Irrigation System....................... A6-10

Appendix-6.6 Summary of Household Survey on the Taklai Irrigation System.................... A6-11

Appendix-6.7 List of Obtaining Document............................................................................ A6-13

Appendix-6.8 Monitoring Plan and Environmental Check List ............................................. A6-18

Appendix-6.9 Estimation of the existing canal section........................................................... A6-23

Appendix-6.10 Environmental Approval .............................................................................. A6-25

Appendix-6.11 Report of geological & soil mechanical investigation ................................... A6-28

・LOCATION M

Gelephu

High level intake (Planed site of

Headwork)

High level canal

Taklai irrigation systems

Taklai irrigation systems

Capital city: Timphu

Site Map of Target area

ﾟ

Gelephu

Location Map

Kingdom of Bhutan

Low level intake

Protection dike at the downstream of

Taklai River

Low level canal

Bhutan

India

Boundary

Taklai river

Exposed part of siphon

Link canal

・LOCATION MAP

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Siph

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・Site photograph

Photo-1：Aspect of the candidate site of the head works(From the downstream) ・Width of river is narrow and big rocks are exposed on both side.

Photo-2：Existing high level intake ・Service water has been supplied from river through digging canal, but the digging canal is washed away each time a flood occurs.

Photo-3：Full view of existing headrace canal ・There is a headrace canal along the right bank, which is protected by the existing gabion wall. If the gabion wall is damaged, the headrace canal will be also damaged and the supply of water will stop.

Photo-4：Close view of existing headrace canal ・There is a worry about boulder stones into the canal because of the ground on the right side of the photo is close to the canal. (There is also a section where boulder stone occurred.)

Photo-5：Damaged condition of high level canal ・The side wall of canal broke down and was not able to maintain the cross-sectional shape. And parts of breakdown stick in the canal and inhibition of its

photo-6：Check gate in the beneficiary area ・It is a condition that user can not operate because there is no spindle.

FLOW

The candidate site of constructing the head works

Main stream of Taklai River

High level intake

FLOW Existing

gabion wall

Existing headrace canal

FLOW

Damaged part of side wall

Loss of spindle

cross section occurred.

Photo-7：Exposure of existing siphon pipe ・There is a worry about damage for exposed pipe by soils and stones from upstream because this stream changes to river during the rainy season.

Photo-8： Damage of existing siphon pipe ・It is a condition that can not supply water because the body of pipe has been damaged.

Exposed part of siphon

List of Figures & Tables

List of Figures

Page

Figure 1-1 Cropping patterns and cultivated areas in the Taklai Irrigation Scheme............. 1-3

Figure 1-2 Marketing channels for rice production in the Chuzagang area.......................... 1-5

Figure 1-3 Location of meteorology observation stations ................................................... 1-9

Figure 1-4 Meteorological condition (average for last 10 years).......................................... 1-9

Figure 1-5 Annual rainfall and maximum daily rainfall in a year for last 10 years ............ 1-10

Figure 1-6 The ratio of rainfall of each rainy and dry season to annual rainfall ................. 1-10

Figure 1-7 Maximum and minimum temperature ............................................................... 1-11

Figure 1-8 Watershed division and location of river discharge observation station ........... 1-12

Figure 1-9 Maximum flood discharge and water depth in the past ..................................... 1-13

Figure 1-10 Location of Mau, Bhur and Sarpang river........................................................... 1-13

Figure 1-11 Project site ........................................................................................................... 1-16

Figure 1-12 Location between project site, and national protected area

and Biological corridors of Bhutan .................................................... 1-17

Figure 1-13 Procedure of Environmental and Social Considerations ..................................... 1-18

Figure 2-1 Image of integrated intake ................................................................................. 2-2

Figure 2-2 Location map of the cooperation Project............................................................. 2-3

Figure 2-3 Canal network diagram........................................................................................ 2-10

Figure 2-4 Transversal cross section of planned site ............................................................ 2-14

Figure 2-5 Profile of downstream side.................................................................................. 2-14

Figure 2-6 Assumed section of the weir body....................................................................... 2-16

Figure 2-7 Section of screen ................................................................................................. 2-19

Figure 2-8 Required length of bar ......................................................................................... 2-20

Figure 2-9 Section of collecting channel............................................................................... 2-21

Figure 2-10 Range of applying apron protective work ........................................................... 2-33

Figure 2-11 Disposition of existing head race and existing gabion revetment ....................... 2-34

Figure 2-12 Vertical section of the river ................................................................................. 2-34

Figure 2-13 Image figure of dissipating.................................................................................. 2-37

Figure 2-14 Cross section of the dissipater ............................................................................. 2-38

Figure 2-15 Cross section of spillway..................................................................................... 2-39

Figure 2-16 Image of repair of rectangular sectioned open channel in headrace.................... 2-40

Figure 2-17 Water level at design flood discharge and water depth around gabion wall ....... 2-44

Figure 2-18 Relationship between Hm/Hn at meandering part and r/B.................................. 2-45

Figure 2-19 Cross section around gabion revetment............................................................... 2-45

Figure 2-20 Section for calculation......................................................................................... 2-46

Figure 2-21 Location of the planned embankment ................................................................. 2-46

Figure 2-22 Flood water level at around the section of planned Dike .................................... 2-47

Figure 2-23 Typical section of Protection Dike ...................................................................... 2-47

Figure 2-24 Location map of construction work on Taklai Irrigation System........................ 2-92

Figure 2-25 Organization for the Project Implementation ...................................................... 2-93

Figure 2-26 Operation and Maintenance System.................................................................... 2-108

List of Tables

Page

Table 1-1 Outline of the project components .................................................................... 1-2

Table 1-2 No. of agricultural machines（January, 2012） ............................................... 1-5

Table 1-3 Items being observed at meteorology observation station ................................. 1-8

Table 1-4 Trend of annual rainfall and maximum daily rainfall in a year ......................... 1-10

Table 1-5 Trend of seasonal rainfall during rainy and dry season ..................................... 1-10

Table 1-6 Maximum and minimum temperature ............................................................... 1-11

Table 1-7 Specification of each kind of river discharge observation station ..................... 1-11

Table 1-8 Estimation results of drought water discharge of Mau,Bhur and Sarpang river 1-14

Table 1-9 Estimation results of drought water discharge at the site of head works ........... 1-14

Table 1-10 Outline of the project components .................................................................... 1-16

Table 1-11 Examination of replaceable alternatives ............................................................ 1-19

Table 1-12 Scoping (Before environmental and social conditions survey) ......................... 1-19

Table 1-13 Assumed TOR of survey for environmental and social considerations ............ 1-21

Table 1-14 Result of survey for environmental and social considerations .......................... 1-22

Table 1-15 Scoping (After environmental and social conditions survey) ............................ 1-22

Table 1-16 Elaboration of negative impact alleviating measures .......................................... 1-25

Table 2-1 Target component（Comparison between Report and Request letter） ............ 2-3

Table 2-2 Basement parameters of the basement at the planned site of the head works ..... 2-5

Table 2-3 Policy of foreign unit water requirement............................................................. 2-9

Table 2-4 Design irrigation area by target canal.................................................................. 2-10

Table 2-5 Design water requirement and design maximum water intake............................ 2-10

Table 2-6 Selection of the location for the construction of the head works ........................ 2-11

Table 2-7 Types of head works and examination of water intake method .......................... 2-13

Table 2-8 Result of hydrological examination at the planned site....................................... 2-15

Table 2-9 Bleigh’s C and Lane’s weighted creep ratio C’................................................... 2-16

Table 2-10 Apron length by means of both formulas ............................................................ 2-17

Table 2-11 Weight of a piece of block and allowable flow velocity ..................................... 2-19

Table 2-12 Calculation of bar-length..................................................................................... 2-20

Table 2-13 Result of the calculation tracing the water surface inside the channel ................ 2-21

Table 2-14 Examples related to designed high discharges and stream.................................. 2-22

Table 2-15 Kind of work methods for apron surface protection............................................ 2-23

Table 2-16 Evaluation indicators based on the basic principles of the design....................... 2-26

Table 2-17 Comparison table of apron protecting work........................................................ 2-27

Table 2-18 Stone pitching work, Work with high strength concrete containing rail ............. 2-28

Table 2-19 Facility environment of Taklai River head works and Yokoe H.W.................... 2-31

Table 2-20 Table of comparison to determine the work to be adopted ................................. 2-32

Table 2-21 Tractive particle size at each level of discharge .................................................. 2-35

Table 2-22 Hydraulic calibration values & examination of applicable bed protection block 2-36

Table 2-23 Standard cross section of the culvert section....................................................... 2-37

Table 2-24 Examination of the scale of dissipater................................................................. 2-38

Table 2-25 Hydraulic calculation of the existing rectangular sectioned canal ...................... 2-40

Table 2-26 Calculation of gradient of sedimentation basin ................................................... 2-40

Table 2-27 Value of allowable marginal precipitation velocity in turbid water .................... 2-41

Table 2-28 Methods of reinforcing the existing gabion protection ....................................... 2-43

Table 2-29 Calculation of water level increase at meandered part of river stream................ 2-44

Table 2-30 Evaluation and treatment of canal flow capacity................................................. 2-48

Table 2-31 Evaluation with visual observation on canals and related structures .................. 2-49

Table 2-32 Cost-sharing division of construction, procurement and installation .................. 2-97

Table 2-33 Quality management plan (Construction period) ................................................ 2-99

Table 2-34 Division of procuring construction materials ...................................................... 2-100

Table 2-35 Table of procurement division............................................................................. 2-100

Table 2-36 Content of activities of soft components ............................................................. 2-102

Table 2-37 Table of schedule of soft component implementation......................................... 2-103

Table 2-38 Estimated project cost of soft components .......................................................... 2-103

Table 2-39 Schedule for implementation............................................................................... 2-105

Table 2-40 Items and contents of the routine / regular inspection......................................... 2-109

Table 2-41 Overall project cost to be borne by the Bhutanese side....................................... 2-110

Table 2-42 Annual budge of CMU........................................................................................ 2-111

Table 3-1 Indicator for the Quantitative effects................................................................... 3-3

Abbreviations

CAFCO Chuzagang Agriculture Farmers Cooperative

CG Chuzagang Geog

CMU Central Machinery Unit

DAS Dzongkhag Agriculture Sector

DoA Department of Agriculture

DoE Department of Energy

DoF Department of Forest and Park Services

ED Engineering Division

EIA Environmental Impact Assessment

GOJ Government of Japan

HLC High Level Canal

HSD Hydro-met Services Division

IEE Initial Environmental Examination

JICA Japan International Cooperation Agency

LLC Low Level Canal

MoAF Ministry of Agriculture and Forests

MoEA Ministry of Economic Affair

MoF Ministry of Finance

NEC National Environmental Committee

NIP National Irrigation policy

RAMC Regional Agriculture Machinery Centre

RDC Research and Development Centre

RGoB Royal Government of Bhutan

RNR Renewable Natural Resource

SG Sershong Geog

TOR Terms of Reference

WUA Water Users Associations

WUC Water Users Committee

Units

1Nu = 1.74Yen

1US$ = 78.24Yen

1 ha = 10,000m2

Kg = 1,000 g

Km = 1,000 m

Chapter 1 Background of the Project

CHAPTER 1 BACKGROUND OF THE PROJECT

1-1 Introduction

Taklai Irrigation Scheme, the largest irrigation system in Kingdom of Bhutan (herein after Bhutan) located in Sarpang district is considered as the key irrigation system serving for the important production area in the south part of the country. This irrigation system was completed in the 1980’s with having due support by United Nations World Food Program (WFP), United Nations Development Program (UNDP) and others. The system was planned aiming at double cropping of rice, as of construction completion ,for the 1,300 Ha beneficiary areas for 756 farm households, whereas, 883 Ha beneficiary areas for approx. 530 farm households as of 2011. Largely, the system can be divided into two (2) parts, one served by high level canal and the other by low level canal. It is expected that attaining enlarged rice cropping in dry season through restoring the subject irrigation system function will greatly contribute to raising up of self-sufficiency ratio of rice at the national level and also to improvement of agricultural productivity in Sarpang district.

However, those existing intake facilities and main canals of the system have been suffering from flood damages almost every year, due to its being located near the Taklai River, which changed its river water route so often. Furthermore, it is noteworthy to mention, that the repair cost for the incurred damages is considered a big burden to the responsible agency. Also, repair works remain at provisional level only. Considering the present situation, it would seem to be difficult to consider a stable and quantitatively adequate irrigation water supply. In addition, the flood that occurred in September 2010 heavily damaged the existing intake facilities and main canal to an extent never experienced before. For the said damages, the government is trying to implement emergency rehabilitation works partly on the system. However, there is a need to urgently undertake comprehensive rehabilitation works for the intake facilities in a sustainable manner for higher durability of the system.

Under the circumstances as mentioned above, the Government of the Kingdom of Bhutan requested government of Japan for technical on June 2011 as well as economic cooperation for the improvement of the system for stable irrigation water supply by the permanent structures.

1-2 Outline of the preparatory survey

The purpose of the project study is to improve and restore the functionality of Taklai irrigation system, the largest irrigation are in Bhutan, and contribute in the increase in rice self-sufficiency and expansion of agricultural productivity in the area.

And the project is formed by discussion with Bhutanese based on the request letter from Bhutanese and result of site survey, in addition, the planned project components are same as written items in request letter, there is no any additional or cancel items. Site survey schedule were as follow;

The first site survey : Middle of January 2012~ Middle of February 2012 (31 days)

The second site survey : Middle of September 2012~ End of September 2012 (10 days)

1-1

Table 1-1：Outline of the project components

Item of facility Description

1. Integrated Headwork ･Fixed Weir：L 38.9m x 1.0m ･Bed protection：L=30.0 m

2. Head race and sedimentation basin

･Box culvert：L= 358.9m ･Open canal：L= 631.2m ･Sedimentation Basin：L= 37.5m ･Retaining wall：H 3.9m x L 410m

3. Link canal ･Rise up wall：L= 654.6m ･Improvement：L= 109.6m

4. Confluence between Link canal and Low level intake

･L type retaining wall H 2m x L 4.65m ･Newly constructing gate：one (1) gate

5. High Level canal

･Wet masonry：L= 123.7m ･Rise up wall：L=165m ･Covered by concrete：L= 205.8m ･Rehabilitation of leakage at 2nd siphon outlet：Covered by concrete･Rehabilitation of leakage at aqueduct：L=50m ･Safe fence around siphon：6 nos. ･Improvement of siphon：covered by reinforce concrete ･Concrete bridge：re-construction (width 4m) x 2 bridges

6. Exposed siphon pipe on High Level Canal ･Protection of exposed siphon pipe at 3rd siphon L= 45m

7. Gate on High and Low Level Canal ･High Level Canal : Check and distribution gate：10gates ･Low Level Canal : Check gate：2gates

8. Water gauge at integrated headwork ･Water gauge：Sound wave type 1 set

9. Protection dike at downstream of Taklai River

･Dike：W 4.0m x H3.0m x L 340m ･Retaining wall：H 3.9m x L 340m

10. Soft component ･ Instruction and assistance for operation of facility, water management, maintenance

1-3. Agriculture

1-3-1 Land Ownership

The Taklai Irrigation Scheme can split into 2 areas, Chuzagang and Sershong area. The results of the

workshops in the both area will be shown in 6-5. Attachment-1. The Chuzagang area is located in both

the upstream (upper) and the downstream (lower) sites and the Sershong area is located in only the

upstream site. The population in the Chuzagang area is even larger than that in the Sershong area.

Although 450 households have been registered in the Chuzagang area, the Water Users Committee

(WUC) estimates that 700 households live. In addition, there are 78 households in the Sershong area.

A total population of beneficiaries in the Taklai Irrigation Systems is 4,308.

In a farmer household survey, 29 households were interviewed. It was found that on average a

household owns 1.83ha of cultivated areas and 1.03ha of irrigation areas (6-5. Attachment-2). In the

Takilai Irrigation Scheme, the government provided an average of 2.2ha lands to each household of the

Sershong area in 1975 and same 2ha lands to each household of the Chuzagang area at the end of

1990s. The household in the Sershong area also received 1.7ha of orange farms and 1.7ha of

1-2

cardamom farms in addition to the land of the Taklai Irrigation Scheme. Moreover, although only 450

households received the lands as already described, the land per household has been reduced because

of increased population in the area by inheritance. Thus, since the policy provided the lands equally to

the people was taken by the government, it can be found that few farmers dominate large areas of

lands and have an advantage in this scheme. Thus, the scheme benefits many households.

1-3-2 Crops

A most important crop in the Taklai Irrigation Scheme is rice and it is cultivated in 44% of the

scheme which counts 488ha. In addition to rice production, the irrigation has mainly been used for

kitchen gardens. On the rained fields, various crops are cultivated and ginger and betel nuts are

particularly important as cash crops. Furthermore, many farmers cultivate maize twice in a year. Dal

can also be found on the same land as intercropping of maize from August to December. Total

cultivated areas of each crop and cropping patterns in the Taklai Irrigation Scheme are found in the

Figure. 1-1.

Area (ha)

472

10

18

2

62

6

6

Harvest depends on market price 37

111

75

28

36

57

182

292

Dry season Rainy season Dry season

Harvest

Fallow

Foxtail Millet

Dal

betel nut

Maize (Mar-Jun）

Maize (Aug-Dec)

Millet

Kitchen Garden

Fish Pond

Rai

nfed

Rice

Ginger

Dec

Irrig

ated

(Ir

rigat

ion

+ R

ainf

ed)

Rice

Spring Rice

Buckwheat

mustard

Jun Jul Aug Sep Oct NovJan Feb Mar Apr MayCrop

Figure. 1-1, Cropping patterns and cultivated areas in the Taklai Irrigation Scheme

1-3-3 Rice Production

As the Figure 3-1 shows, rice is cultivated from April to December. Generally, the farmers conduct

ploughing, preparation for nursery, land preparation and transplanting from April to July and harvest

from November to December although the timing depends on the varieties. Seasons particularly needs

water are land preparation from May to July and flowering stage of rice from September to October. In

these seasons, the farmers basically use irrigation water. Spring rice and rainfed rice are also produced

on the 16 ha farmland.

The farmers on the scheme generally do not utilize fertilizer such as NPK and urea. Nutrition is

provided to soil by supplying animal manure collected in cattle sheds or by letting cattle grazing and

1-3

restoring its manure.

In addition, though it is recommended to renew their rice seed every three to four years, the farmers

keep using their harvested rice for a long time. They may simply exchange it with the other farmers,

but they hardly renew the seed by purchasing.

In addition, rice sold through the Chuzagang Agricultural Farmers Cooperative (CAFCO) is mostly

local varieties. This implies that rice produced in the Taklai Irrigation Scheme is also local varieties.

Thus, it can be said that the farmers in the Taklai Irrigation Scheme are engaged in a low-input and

low production farming system. This may be a reason for that rice yield is relatively low, which is

2ton/ha on an average, in Sarpang District by comparison with the other districts. In Bhutan, an

average yield of rice production is 3.1ton/ha and that of Sarpang District is 19th out of the 20 Districts.

1-3-4 Utilization of Agricultural Machinery and Animal Draft Power

The result of the farmer household survey shows that a half farmers use agricultural machines such as

a tractor and a rotary for the land preparation and the other half farmers utilize draft cattle for it.

Particularly, because there are many stones and rocks on the field of the Sershong area, all the farmers

cannot plough with using such machines and use draft cattle.

As the table 3-1 describes, most agricultural machines on the Taklai Irrigation Scheme, particularly

large machinery, are managed by the CAFCO and farmers are able to borrow them from it. In this case,

an operator is also sent by the CAFCO. These machines are originally lent by the Regional Agriculture

Machinery Center (RAMC) without any payment. Farmers can pay the rental fee in kind as rice or in

cash. According to the CAFCO’s manager, 60% of them pay in kind and 40% pay in cash. The

machines are maintained by the CAFCO but when a high skill is required for the repair, the CAFCO

requests to the RAMC.

For instance, in 2011, 4 tractors were lent to the 162 households and utilized for the land preparation

of 224ha farmland. This accounted for a half of the paddy field in 2011. Annual operating hours per

tractor is 651 hours in total. If the daily operating hour is considered as 8 hours, the annual operating

days can derive 81 days and imply that it is optimized. In addition, as the Table 1-2 shows,

approximately a half of tractors owned by the RAMC in Sarpang District are lent to the CAFCO.

Thus, it can be predicted that even the RAMC does not own enough machines and this may not allow

the farmers in the scheme to borrow more machines. The results of the farmer household survey report

that around 40% of farmers pointed out a lack of labor as a problem. This expects rapid repair of

agricultural machines by the RAMC and more inputs of agricultural machines in the future.

On the current condition, the agricultural machines at the CAFCO are stored or under repair during

the fallow period. More utilization of the machines in winter season would be expected by

encouraging double cropping.

1-4

Retailer (Thimphu)

Farmer CAFCO Trade show

Middleman Retailer

(Thimphu)

Consumer

(Timphu and

Gelephu) 17Nu/kg

(Unhusked

Rice) 28Nu/kg

(Polished

Rice)

42Nu/kg

(Polished

Rice)

39Nu/kg

(Polished Rice)

39Nu/kg

(Polished Rice)

45Nu/kg

(Polished

Rice)

52Nu/kg

(Polished Rice)

48Nu/kg

(Polished

Rice)

①

②

③

Actual Route

2010：①50%③50%

2011：①10%②80%③10%

Figure 1-2, Marketing channels for rice production in the Chuzagang area

Table 1-2. No. of agricultural machines（January, 2012）

Items Taklai Irrigation Scheme*1

CAFCO RAMC（Samteling, Gelephu）*3

Tractor 9 7*2 12 Plough 7 5 7

Rotorvator 8 7 4 Rice huller 12 0 0

Rice milling machine 1 1 1 Power tiller 12 2 －

Cattle for drafting 290 0 0 Harvester 5 3 6

Rice planter 2 2 2 Truck (ton capacity) 8 8 1

Flower mill 12 0 1 Pedal thresher 21 － －

*1 Including the machines owned by the CAFCO *2 5 of tractors are under repair *3 No. of agricultural machines the RAMC owns in whole areas of Sarpang District

1-3-5 Role of Female and Male on Rice Production and Work Sharing

Males engage in hard works and females are in charge of works by hand in the Taklai Irrigation

Scheme. For instance, while the males engage ploughing, land preparation, making and clearing levee,

threshing, and transporting, the females are responsible for preparation of seedling, up-rooting

seedling, transplanting, weeding, harvesting, winnowing and transporting. There is no difference of

working hours between the female and the male on cropping season and the average is 8.4hours.

In addition, work sharing on rice production is also common in the scheme. On an average, 21 people

are working together as a group and split into a male group and a female group. In case a family does

not have enough labor to participate, the working group is paid and contracts the works.

During fallow season, many young males engage contract works at construction site. To start double

cropping in the Taklai Irrigation Scheme, there may be a concern that only females increase their work.

However, according to the interview, many males also are willing to be engaged in spring cropping on

their own farmland rather than working outside and it could be expected that males also participates it.

1-3-6 Marketing

The Figure 1-2 describes marketing channels for rice production in the Chuzagang area on the Taklai

Irrigation Scheme.

1-5

Most farmers on the Taklai Irrigation Scheme produce rice for home consumption and meet 100% of

self sufficiency. A few farmers sell surplus rice and earn 2,200 Nu per year. The farmers selling surplus

rice target the CAFCO as a market cannel. There are also farmers selling at Chuzagang, Gelephu and

Thimphu directly with using a rice huller within the area. However, such farmers are limited and

amount of sales is a little.

Although 993 tons of rice are produced on the scheme in 2011, only 56 tons of unhusked rice (could

be converted to 37 tons of polished rice) were sold. As already described above, this figure includes

the rice paid for borrowing of agricultural machines to the CAFCO. It can be estimated that the

farmers who sold purely surplus rice may be negligible.

While capacity of the milling plant managed by the CAFCO is 1.5 tons of unhusked rice per hour, it

could be calculated that the plant is utilized only 37 hours per year in 2011.

The milling plant was installed in 2008 by funds from the European Union and also maintained by

the CAFCO staffs who received technical training from Indian Engineers. Hence, it can assume that

the performance may be optimized. If the irrigation area is expanded and the rice production is

increased, the plant may meet processing capacity. Thus, commercialization of rice production can be

expected with effective use of the plant.

In addition to rice, maize, Dal, green manure and eggs are sold through the CAFCO. Furthermore,

ginger and betel nuts are important as cash crops. Ginger is sold from each farmer to Indian retailers

through auction at Gelephu regulated by the Food Cooperative of Bhutan (FCB). In this case, both

farmers and retailers should pay a commission fee to the FCB.

Moreover, middlemen from the Chuzagang area directly visit each farmers’ field, oversee the product

quality and negotiate with farmers. After that, they sell the betel nuts to Indian retailers. In addition to

the betel nuts, Dal is also marketed through middlemen.

The Fishery Farmers Group, members of the CAFCO, works at fish ponds within the area and sells

their products locally.

1-3-7 Agricultural Extension

The governmental extension services are provided by the DAS. 2 officers are allocated in the Sector

and play role on coordination of extension activities, designing plans and monitoring. On the field, the

Renewable Natural Resources (RNR) is responsible for actual extension works. Each geog in Sarpang

Dzongkhag has a RNR office where 3 extension workers from agriculture, livestock and forest sector

are assigned.

Plans of extension activities depend on farmers’ expectation and budget. Then, training for farmers is

conducted 3 to 4 times per year. For designing the plan, the Training Needs Assessment (TNA) is hold

1-6

with farmers and they suggest the activities. The suggestions are reported to the Dzongkhag level and

the officers finalize the plan. In this project, the DoA should communicate with extension workers in

the Taklai Irrigation Scheme though Dzongkhag Agriculture Sector.

Currently, green manure production has been introduced to the Taklai Irrigation Scheme. First, the

techniques were examined by the RDC and the results were reported to the Dzongkhag Agriculture

Sector. Then, the sector designed the plan, coordinated the activities and encouraged the RNR staffs to

launch extension services.

According to the RDC, the RDC officially works with the RNR through coordination by the

Dzongkhag Agriculture Sector. However, it is more often for them to have a meeting directly with the

RNR to discuss extension services and their activities.

Basically, a lecturer of the training is done by the extension officers at the RNR. In case they require

high techniques and knowledge, they can call a commodity coordinator who is a expert from the

central, the DoA. The budget per farmer is 200Nu/day. In addition, the budget for materials used at the

training is also allocated.

The budget on the extension services are prepared by each extension worker at geog levels and

submitted to the Dzongkhag Agriculture Sector and geog administration. Then, they report to the

budget to the Ministry of Finance through the DoA, the Dzongkhag Adinistration and Head of

Dzonkhag.

In addition to the training for famers, there is training for the extension officers. The contents are

designed by the DoA and 4 trainings were conducted for 3 Dzonkhags jointly in 2011. Commodity

officers from the DoA and officers from the other research center are assigned as the lecturers.

1-3-8 Agricultural Associations and Cooperatives

The farmers’ organizations working on the Taklai Irrigation Scheme are the WUA (Water Users

Associations) and the CAFCO. In relation to the WUA, the 3-6 will describe a detail. Hence, contexts

of the CAFCO will be explained here.

The CAFCO is an agricultural cooperative in the Chuzagang area and composed of 8 groups such as

the Saving Group, Poultry Farmers Group and Fishery Farmers Group. In total, 153 households and

200 people are participating (January, 2012). It was established in August of 2010 and approved as an

official cooperative.

4 farmers have been employed and their salary is 2,500Nu/month・person in January of 2010. In

addition, a manager from the DoA has also been assigned to enhance their administration. As already

described, the CAFCO plays role on maintenance of agricultural machines lent by the RAMC and

lending them to the farmers in the area, collecting unhusked rice, marketing, running a local a retail

shop and the other activities of each group.

1-7

They have made efforts to secure official markets and participate in trading show. In addition, they

are able to keep a proper record on the administration. Thus, it can expect that they play a crucial role

on proper maintenance of agricultural machine, processing increased agricultural products and

capturing more market cannels.

The famers in the Sershong area do not have agricultural cooperatives such as the CAFCO, many

famers sell crops by themselves rather than through cooperatives or groups. This may be a reason that

farm gate price of unhusked rice in the Sershong area is lower than that in the Chuzagang area.

Because people from the other geogs can also join the CAFCO, it expects that the CAFCO leads

people in the Sershong area to participate and work jointly.

1-4 Natural condition

1-4-1 Topographic, Geological and Climatic classification

Topographically Bhutan is divided into 4 zones with its geological condition, I) Greater Himalayan

zone, II) Lesser Himalayan zone, III) Sub-Himalayan zone and IV) Quaternary sediment zone. Taklai

Irrigation Area is located within IV) Quaternary sediment zone. Quaternary sediment zone consist of

alluvial fan and river terrace developing on the mountain foot along the boundary to India. Since its

altitude is 200 - 400m with mild slope, agricultural potential of this zone is high.

Climatic classification of Taklai Irrigation Area is Humid and Wet Sub-tropical zone.

1-4-2 Meteorological condition at Taklai Irrigation Area

(1) Structure of meteorology observation

There are 2 classes of observation station for meteorological condition. Items being observed at each

class of station and location of observation stations are mentioned in the table and figure below.

Table 1-3: Items being observed at meteorology observation station

Class Class A Class-C

Observed items

Daily rainfall (mm/day) Maximum Temperature ( C) Minimum Temperature ( C) Relative Humidity (%) Wind Speed (m/s) Wind Direction Sunshine (hr) Cloud Cover (oktas)

Daily rainfall (mm/day) Maximum Temperature ( C) Minimum Temperature ( C)

1-8

Fig 1-3: Location of meteorology observation stations

Since Taklai Irrigation Area has no meteorological observation stations within its catchment area, its

meteorological condition is examined using record at Bhur observation station (Class-A, altitude 375m,

location: RNR Research and Development Center) due to its similarity of natural condition as Taklai

Irrigation Area.

Meteorological condition of Bhur and Thimphu observation station (Class-A, altitude 2,380m,

location: MoEA complex) are shown in the figure below. On the following pages, record of Thimphu

observation station is also shown as reference.

Fig 1-4: Meteorological condition (average for last 10 years)

(2) Rainfall

a) Annual rainfall and Maximum daily rainfall in a year

Annual rainfall and maximum daily rainfall in a year for last 10 years are shown as following,

Monthly rainfall Maximum temperature Minimum temperature

-20

-10

0

10

20

30

40

50

0

200

400

600

800

1,000

1,200

1,400

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Tem

pera

ture

(deg

ree)

Mon

thry

rain

fall

(mm

)

Thimphu: 2002-2011

Annual Rainfall 650mm

Taklai Irrigation Area Bhur

Thimphu

：Meteorological observation station(Class-A) ：Dzongkhag boundary

：National boundary

-20

-10

0

10

20

30

40

50

0

200

400

600

800

1,000

1,200

1,400

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Tem

pera

ture

(deg

ree)

Mon

thry

rain

fall

(mm

)

Bhur: 2002-2011

Annual Rainfall 5,120mm

1-9

Table 1-4: Trend of annual rainfall and maximum daily rainfall in a year

Bhur observation station Thimphu observation stationAnnual rainfall Almost no trend Decreasing Maximum daily rainfall in a year Increasing Increasing

Fig 1-5: Annual rainfall and maximum daily rainfall in a year for last 10 years

b) Rainfall during each monsoon and non monsoon season

Seasonal rainfall during each rainy and dry season for last 10 years are shown as following,

Table 1-5: Trend of seasonal rainfall during rainy and dry season

Bhur observation station Thimphu observation station The ratio of rainfall during monsoon season to annual rainfall is increasing.

The ratio of rainfall of each monsoon and non monsoon season to annual rainfall has almost no trend.

Fig 1-6: The ratio of rainfall of each rainy and dry season to annual rainfall

Additionally, since annual rainfall at Bhur observation station has almost no trend but maximum

rainfall in a year is increasing (show Fig 1-3), rainfall intensity during monsoon season at Bhur

observation station seems to be increasing.

0

10

20

30

40

50

60

70

80

90

100

0

100

200

300

400

500

600

700

800

900

1,000

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Max

imum

dai

ly ra

infa

ll(m

m)

Ann

ual r

ainf

all (

mm

)

Thimphu: 2002-2011

0

50

100

150

200

250

300

350

400

450

500

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Max

imum

dai

ly ra

infa

ll(m

m)

Ann

ual r

ainf

all (

mm

)

Bhur: 2002-2011

Annual rainfall Maximum daily rainfall

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Bhur: 2002-2011

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Thimphu: 2002-2011

Rainfall in Non Monsoon Season / Annual Rain Fall Rainfall in Monsoon Season / Annual Rain Fall

1-10

(3) Temperature

The month having maximum temperature in a year is August and minimum is January at both Bhur

and Thimphu observation station. Maximum and minimum temperature for last 10 years are shown as

following,

Table 1-6: Maximum and minimum temperature

Bhur observation station Thimphu observation stationMaximum temperature Decreasing Increasing Minimum temperature Decreasing Increasing

Fig 1-7: Maximum and minimum temperaturel

1-4-3 Hydrological condition at the site of head works

(1) Watershed division and Structure of river discharge observation in Bhutan

Rivers in Bhutan are managed according to watershed division, 3 large watershed and 11 middle

watershed.

There are 3 kinds of river discharge observation station. Specification of each kind and location of the

stations are shown in the following table and figure.

Table 1-7: Specification of each kind of river discharge observation station

Kind Observed items and Equipment Frequency of observation Reporting

Water level gauge Water level : Twice a day

(9:00 and 15:00)

Current meter Observation of discharge :

Once a week

Principal Station

Digital recorder

Water level : Once a day (9:00)

Observation of discharge : Once a day

Secondary Station

Water level gauge

*) Float type current meter

Observation is done from January to March.

-10

-5

0

5

10

15

20

25

30

35

40

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Tem

pera

ture

(deg

ree)

Bhur: 2002-2011

-10

-5

0

5

10

15

20

25

30

35

40

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Tem

pera

ture

(deg

ree)

Thimphu: 2002-2011

Maximum temperature for August Minimum temperature for January

Maximum Minimum Average

1-11

Kind Observed items and Equipment Frequency of observation Reporting Spot Low Flow Measurement

Current meter (Propeller type)

Observation of discharge : Once a year

Source : Surface Hydrological data of Bhutan 2009, Department of Energy

Source : Surface Hydrological data of Bhutan 2009, Department of Energy

Fig 1-8: Watershed division and location of river discharge observation station

(2) Hydraulic regime at the site of head works

a) Hydraulic regime during study period

Taklai river on which head works are planned to be constructed has no record of its discharge.

Although it is just for reference, river discharge at the head works construction point has been

measured through this study to grasp the specification of river discharge.

As results of measurement, drought water discharge measured during non monsoon season seems to be

usable data. However since amount of flood discharge measured during monsoon season is different

from that estimated by rational formula mentioned below, it seems difficult to be usable data.

b) Estimation of Flood discharge

Flood discharge at the site of head works is estimated according to the following 2 means.

i) Estimation using rainfall data at Bhur observation station

ii) Estimation using flood trace at the site

Taklai Irrigation System

: Principal Station : Secondary Station : Boundary of large watershed

1-12

As a result of estimation using rational formula, 1,710m3/s is calculated as flood discharge with

50years occurrence probability.

=1,710m3/s

Q: peak flood discharge (m3/s),

f: coefficient of discharge (=0.7),

r: average rainfall within flood reaching time (=102 mm/hr),

A: catchment area (= 86.24km2)

ii) Estimation using flood trace at the site

The 6m depth of past flood trace is observed at the site. In this case, 1,330m3/s of river discharge is

calculated as the past maximum flood discharge, according to the hearing at the site.

Fig 1-9: Maximum flood discharge and water depth in the past

c) Estimation of drought water discharge

Drought water discharge at the site of head works is estimated according to the following 2 means.

i) Measurement result of discharge at the site

ii) Estimation using discharge data at the other rivers with similar natural condition as Taklai

Irrigation system

i) Measurement result of discharge at the site

Discharge measured at the site of head works on 1st February, 2012 was approximately 3.8m3/s.

ii) Estimation using discharge data at the other rivers with similar natural condition as Taklai Irrigation

system

Rivers having similar natural condition as Taklai

Irrigation System are Mau River, Bhur River and

Sarpang River. At these rivers, minimum water

discharge is measured once a year during January to

March. Analysis results of drought water discharge of

each river are shown in the table below. Unit

discharge of each river is almost same.

Fig 1-10 Location of Mau, Bhur and Sarpang river

1-13

Table 1-8: Estimation results of drought water discharge of Mau, Bhur and Sarpang river

Drought water discharge (m3/s) (Unit discharge (m3/s/km2))

River Catchment

area (km2) 1time

/10years1time

/5years 1time /1year

Maximum in last 5years

Second maximum in last 10years

Remarks

Mau River

744.638.1644

(0.0110)8.7004

(0.0117)9.7948

(0.0132) 7.7510

(0.0104) 7.9610

(0.0107) 1992 - 2007

(Excluding 1993) Bhur River

81.000.8157

(0.0101)0.8776

(0.0108)1.0111

(0.0125) 0.8260

(0.0102) 0.8080

(0.0100) 1993 - 2008

(Excluding 2004) Sarpang

River 135.25

1.4033(0.0104)

1.5326(0.0113)

1.8140 (0.0134)

1.6930 (0.0125)

1.5940 (0.0118)

1995 - 2008

Average of unit discharge

(m3/s/km2) 0.0105 0.0113 0.0130 0.0110 0.0108

Estimated drought water discharge at the site of head works multiplying average of unit discharge

shown in the table above and catchment area at the site is shown in the table below. As a result,

1.1211m3/s is calculated as drought water discharge with 1year occurrence probability.

Table 1-9: Estimation results of drought water discharge at the site of head works

Drought water discharge (m3/s) (Unit discharge (m3/s/km2))

River

CatchmentArea at the

site (km2)

1time /10years

1time /5years

1time /1year

Maximum in last 5years

Second maximum in last 10years

Remarks

Taklai River

86.24 0.9055 0.9745 1.1211 0.9486 0.9314

1-4-4 Effects of earthquake

Generally, civil structure constructed under the ground or having no protrusion does not suffer damage

from earthquake. Although Bhutan has suffered damage from earthquake due to its location on the

border between Eurasia and Indian plate, since Taklai Irrigation System has no protrusion, seismic

force is not considered for design.

1-4-5 Geological survey

The geological survey conduct to study the feature at candidate site for headworks. The contents of

survey is shown as follows;

① Boring (Including the sounding) : 2 boring, right and left bank x depth 10 meter around

Candidate site of headworks, and 2 boring on center of river

x depth 5 meter around Candidate site of headworks

② Standard penetration test (SPT) : Each 1 meter depth, totally 26 nos.

③ Sampling for Laboratory test : 10 nos.

④ Result

1-14

Geological formation in and around the planned site of head works can roughly be classified into

gravel and pebbles over the stream-bed and quartzite / gneissic boulder derived from volcanic origin

materials judging from the result of a geologic survey. Both of these strata are relatively compact

judging from the measurement results with 35° or larger for their internal friction angle and about

2.0tf/m3 as unit weight.

1-4-6 Topographic survey

The topographic survey conduct to study the basic condition. The contents of survey is shown as

follows;

① Candidate site of headworks : Check the bench mark and longitudinal and cross section survey

② Main canal (High and Low) : Check the bench mark and longitudinal and cross section survey

③ Link canal : Check the bench mark and longitudinal and cross section survey

④ Related structure on the main canals : Inventory survey and make drawing

⑤ Candidate site of protection dike : Check the bench mark and longitudinal and cross section survey

1-5 Environmental and Social Consideration

1-5-1 Preparation and submission of Initial Environmental Examination (IEE) Report

As this Project include new construction of weir and rehabilitation of the existing canal, it is subject

to the application of Initial Environmental Examination (IEE) in compliance with “Processing

Environmental Clearance for Irrigation Construction Projects: A Guide for Proponents (October

2004)”. It follows that application for environmental report on IEE has to be submitted to NEC. NEC

issues the environmental permit provided that the contents of the report of IEE satisfy the conditions

for environment conservation.

1-5-2 Procedure for securing environmental approval

NEC confirmed that the subject project is a development project and IEE report must be submitted to

the Authorities concerned. Accordingly, DoA prepared the IEE report on the schemes with having

due assistance by the JICA survey team and submitted the IEE report to the NEC on August 28, 2012.

The IEE report was carefully considered by NEC and it was on 2nd November 2012 that the

Environmental Approval was duly issued. (Ref. Appendix- 6.10).

1-5-3 Environmental Impact Assessment

(1) Outline of the Component of Environmental Impact

The project is categorized as agricultural project and the components as follows;

1-15

Table 1-10：Outline of the project components

Item of facility Description

1. Integrated Headwork ･Fixed Weir：L 38.9m x 1.0m ･Bed protection：L= 30.0 m

2. Head race and sedimentation basin

･Box culvert：L= 358.9m ･Open canal：L= 631.2m ･Sedimentation Basin：L= 37.5m ･Retaining wall：H 3.9m x L 410m

3. Link canal ･Rise up wall：L= 654.6m ･Improvement：L= 109.6m

4. Confluence between Link canal and Low level intake

･L type retaining wall H 2m x L 4.65m ･Newly constructing gate：One (1) gate

5. High Level canal

･Wet masonry：L= 123.7m ･Rise up wall：L=165m ･Covered by concrete：L= 205.8m ･Rehabilitation of leakage at 2nd siphon outlet：Covered by concrete･Rehabilitation of leakage at aqueduct：L=50m ･Safe fence around siphon：6 nos. ･Improvement of siphon：covered by reinforce concrete ･Concrete bridge：re-construction (width 4m) x 2 bridges

6. Exposed siphon pipe on High Level Canal ･Protection of exposed siphon pipe at 3rd siphon L= 45m

7. Gate on High and Low Level Canal ･High Level Canal : Check and distribution gate：10gates ･Low Level Canal : Check gate：2gates

8. Water gauge at integrated headwork ･Water gauge：Sound wave type 1 set

9. Protection dike at downstream of Taklai River

･Dike：W 4.0m x H3.0m x L 340m ･Retaining wall：H 3.9m x L 340m

10. Soft component ･ Instruction and assistance for operation of facility, water management, maintenance

In this project does not assume the great impact or damage to environment considering above project

component. However, there are possibly negative impact in a part of area, therefore this project is

categorized into " Category B" based on " JICA Guidelines for Environmental and Social

considerations (the new Guidelines, April 2010)"

Fig 1-11 : Project site

1-16

(2) Condition of Basic Environment and Society

Bhutan has 10 national parks and project site is at close Royal Manas national park of west side. This

area is 2,873 km2 which divided between Buffer Zone : 2,446km and Core Area : 391km2. In addition,

those are observed humid and grass covered area, semi-Himalaya humid and deciduous forest,

semi-Himalaya alpine humid and evergreen forest and lowland humid savannah. Furthermore, there

are almost 20 animals which are in danger of extinction, therefore these area is important for the

species preservation.

In site survey, the team made sure that location of national park is the left bank of Taklai river and

project site is outside of these national protected area. Finally, the project scarcely give an

environmental influence to that park.

Fig 1-12 : Location between project site, and national protected area and Biological corridors of Bhutan

(3) Procedure of environmental and social considerations

The regulation of the environmental in Bhutan comply with "① Environmental Assessment Act 2000",

"② Regulation for the Environmental Clearance of Project (2002), "③National Environment

Protection Act of Bhutan, 2007.

A flow chart of procedure for the environmental assessment is shown on Fig 1-13. According to the

flow chart, National Environmental Committee (NEC) assess the monitoring and evaluation for the

designed irrigation plan based on above latest lows. After the assessed by NEC, NEC will issue the

environmental approval, then DoA which is executive agency in this project, will start the project

Project site

1-17

follow the environmental regulation by NEC.

An application for the environmental and social considerations in Bhutan is of the Processing

Environmental Clearance for Irrigation Construction Projects : A Guide for Proponents (October 2004).

According to that guideline, in case of new construction or large improvement of the irrigation system,

environmental approval should be needed before commencement of construction.

The application submitted by executive agency should be contained the expectation and assessment for the

environmental influence, in addition the measurement as the alleviation or remove for influence should be

described on that application as well as monitoring plan during the construction period in order to confirm

the monitoring performance. Under the condition of filled with above mentioned, NEC will issue the

environmental approval.

DoA, executive agency, will monitor the monitoring performance through the site check in project period.

(4) Alternative Plans

As an examination of alternative activities that can be replaced with this Project, the following three

alternatives are examined by comparison, namely alternative A: the existing state of irrigation

(zero-option), alternative B: cooperation project by JICA (on rehabilitation basis) and alternative C:

new land reclamation (such as new farming settlement). As shown in the following table, it has been

concluded that the alternative B (this Project) is the most feasible among these three.

Dur

atio

n 3

-4

mo

nth

s

Du

ratio

n 1

mo

nth

s

Fig 1-13 : Procedure of Environmental and Social Considerations

1-18

Table 1-11: Examination of replaceable alternatives

Type Content Technical/ financial difficulty

Land use Environmental impact Social impact

Evalu-ation

PLAN-A Existing project (zero- option)

◎The same as it is now

◎The same as it is now

◎The same as it is now

×Since continuous intake is impossible, food production cannot be increased. Repair is necessary every time after floods.

×

PLAN-B The Project by JICA

Techniques to be applied has already been established. Since this Project consists of installation of small scaled weir and rehabilitation of the existing canal, the incurred cost is cheaper than that of the whole new construction

◎Almost the same as it is now, because the project consists of only the installation of a weir and rehabilitation of the canal

Almost the same as it is now

◎The Project enables to secure stable supply of irrigation water distribution, thus increased food production can be expected. Also, employment opportunities are generated from the construction work.

◎

PLAN-C Newly reclaimed development project

×This requires new study, design and construction work to realize.

△Requiring development of new perimeter

△From the necessity of new land reclamation, need of newly evaluating impact to local environment arises.

◎ The same as above column

△

Classification of Evaluation × : No Good △ : Fine ◎ : Very Good

(5) Scooping

The following table gives scoping on impact of the major components included in this Project to

environment and society. This Project does not give any serious impact to the environment and society.

Table 1-12: Scoping (Before environmental and social conditions survey)

Evaluation No Environment Item Under

construction During the

use Reason of judgment

Countermeasures against pollution

1 Air pollution B- D Under construction: On rehabilitation work with heavy machinery, trucks are supposed, but no serious degree of air pollution takes place. However, dust is generated when vehicles pass. During the use: Once offering for use, no impact of air pollution arises.

2 Water pollution B- D Under construction: Accompanying with newly constructing work of the weir, turbid water may occur in the river. During the use: Once offering for use, no impact of water pollution arises。

3 Wastes B- D Under construction: Wastes and scraps (mostly excavated earth) are more or less resulted from excavation and other construction work. During the use: Once offering for use, no waste is generated

4 Soil pollution D D Since this Project has the objective of irrigation water supply, no soil pollution is resulted from the work.

5 Noise / vibration

B- D Under construction: Transport of materials by heavy machinery and trucks are made toward the sites. However, serious noise / vibration is

1-19

Evaluation No Environment Item Under

construction During the

use Reason of judgment

not generate from these activities. However, consideration would be needed to pay when the pass in the living quarters. During the use: Once offering for use, no noise/ vibration is emitted.

6 Land subsidence

D D Since no groundwater lifting is planned in this Project, no land subsidence is supposed.

7 Odor emission D D Since this Project has the objective of irrigation water supply, no cause of odor is resulted from the work.

8 River bottom state

B- C Under construction: Though excavation in river-bed is accompanied with the construction work of the weir, the scale is very limited where the sediment deposit is very little. Almost no detrimental effect is resulted to water quality of the river. During the use: The extent of the protrusion from river bottom is very limited, without giving heavy impact on bottom regimenting or variation of river bed.

Natural environment

9 Eco-system, protection area

D D The sites of construction work in this project are not situated in any protection/ conservation area.

10 Hydrological phenomena

D C Under construction: Since the work in the river is carried out by partly closing the river-bed, the river discharge can directly release to the downstream as before. During the use: The planned quantity of intake is fairly little as compared to droughty water discharge, resulting in very limited impact on the river flow.

11 Topography/ geology

D D Under construction: No plan is included to collect large amount of stones, to excavate or fill large quantity of earth. Since the work is rehabilitating nature, no sizable variation is resulted in topographical and geologic situations of the area. During the use: Once offering for use, no impact on these factors arises

Social environment

12 Evacuation, removal of local population

D D Because the contents of construction in this project include rehabilitation of intake weir in torrential stream, the existing open canals and gates. The section to expand the width is located on public land owned by the government. Therefore, non-voluntary/ forcible removal of the inhabitants does not arise.

13 Vulnerable strata, ethnic minority, aboriginal tribe

D D Any aboriginal tribe or minor ethnic exists in the target Project area. Also, no impact thereon arises from activities of this Project.

14 Such local economy as employment and livelihood means

B+ A+ Under construction: Since hiring opportunities of local inhabitants are generated by the construction work, possibly beneficial impact on local economy is expected. During the use: O/M cost of the existing facilities is economized, increased crop production and subsequent livelihood improvement of farm households are expected accompanied with the improved water distribution service.

15 Water use B- D Under construction: Accompanying with the new construction of weir, some impact by turbid water during the work may happen. During the use: Once offering for use, no impact on water use arises

16

Biased benefit and damage distribution

D D Agricultural benefits arising from this Project are equitably distributed among all beneficially farmers. By this reason, no biased distribution of benefits and suffering is resulted from the Project.

17

Cultural heritages

D D No particular cultural heritage exists within the Project area. No possibility of impact of this Project on the local culture is conceivable.

18

Landscape B- C Under construction: excavation is worked that has very limited extent but has more or less possibility of altering topographic appearance. During the use: Such artificial structures as weir body and revetment are considered to have some possibility of changing surrounding landscape.

19

Labor environment

B- D Under construction: Careful consideration on possible accident during construction is indispensable.

1-20

Evaluation No Environment Item Under

construction During the

use Reason of judgment

(including labor safety)

During the use: Since facilities are rehabilitated, gate operation is made easier resulting in improved labor condition.

Others

20 Accident B- D Under construction: Potential risk would arise from the Project such as possibility of traffic accidents caused by vehicles of the construction work giving damages to local inhabitants, those caused by heavy machinery during rehabilitation of open canals and gates etc. During the use: No impact on the ambient environment because of mere rehabilitation of the existing canals.

21

Territory transversal impact and risk of climatic variation

D D Taklai River over which the weir is installed is a tributary of Mao River flowing down to India, but no fluvial agreement has been concluded. Either, sizable change in the flow that can induce climatic variation is not evolved from this construction work.

Evaluation classes: A+ : Particularly positive impact is brought by the activity, A- : Particularly negative impact is brought by the activity, B+ : Positive impact is brought by the activity, B- : Negative impact is brought by the activity, C : The extent of the impact is unknown and D : No impact arises from the activity

(6) TOR of the survey for environmental and social considerations

As the result of scooping, the items evaluated "B-" as an integrated evaluation which are 1. Air

pollution, 2. Water pollution, 3. Wastes, 5. Noise / vibration, 8. River bottom state, 15. Water use, 18.

Landscape, 19. Labor environment, 20. Accident, is mentioned as follows. No. 2. Water pollution and

No.18. Landscape, however, are not occurred a substantial impact to the project, therefore these items

exclude from the Term of reference (TOR).

As the TOR, the assumed the way of survey and contents for environmental and social considerations

is shown as follows (Table 1-13);

Table 1-13: Assumed TOR of survey for environmental and social considerations

No. Items for environment Items for check How to check 1 Air pollution Impact during construction ･Check the fugitive dust on driving

truck or car 3 Wastes Impact during construction ･Check the disposal way of generated

waste 5 Noise / vibration, Impact during construction ･Check the components of construction,

the way, period, range, kind of construction machine, number of driving truck

･Check the residence area whether near the construction site is and carry out the hearing.

8 River bottom state Impact during construction ･ Check drainage condition on excavating the river

15 Water use Impact during construction ･ Check drainage condition on excavating the river

19 Labor environment Accident during construction ･Check the components of construction, the way, period, range, kind of construction machine, number of driving truck

･Conduct site survey and hearing 20 Accident Impact and accident during

construction ･Check the components of construction,

the way, period, range, kind of construction machine, number of

1-21

No. Items for environment Items for check How to check driving truck

･ Conduct site survey (traffic )and hearing

(7) Result of the survey for environmental and social considerations (include the expectation)

The result of the survey for environmental and social considerations include the expectation based on

scooping, are shown as follows;

Table 1-14: Result of survey for environmental and social considerations

No. Items for environment Measurement 1 Air pollution ･the fugitive dust generate on driving truck or car 3 Wastes ･Excavated soil and construction waste are generated, but almost excavated soil. 5 Noise / vibration, ･Transportation of the materials and so on by truck is carried out, the noise,

however, is not serious. Need to pay attention through near the residence area. 8 River bottom state ･Excavated soil is generated, however, it is not large. The bed excavation work for

the headwork is carried out, however, the muddy water is not almost occurred and given the impact.

15 Water use ･It is conceivable that muddy water is occurred during construction of headwork 19 Labor environment ･Pay attention for the accident during construction 20 Accident ･Traffic accident between residence and truck of construction works is possibly

occurred when rehabilitation works for canal and gate is carried out.

(8) Assessment of environmental and social considerations

Some impact is inevitable although, the serious impact for environment is avoidable by the proper

measurement.

Table 1-15: Scoping (After environmental and social conditions survey)

Evaluation at Scooping

Evaluation after the survey

No Environment Item Under constructio

n

During the use

Under constructi

on

During the use

Reason of judgment

Countermeasures against pollution

1 Air pollution B- D B- N/A Under construction: On rehabilitation work with heavy machinery, trucks are supposed, but no serious degree of air pollution takes place. However, dust is generated when vehicles pass. During the use: Once offering for use, no impact of air pollution arises.

2 Water pollution B- D B- N/A Under construction: Accompanying with newly constructing work of the weir, turbid water may occur in the river. During the use: Once offering for use, no impact of water pollution arises。

3 Wastes B- D B- N/A Under construction: Wastes and scraps (mostly excavated earth) are more or less resulted from excavation and other construction work. During the use: Once offering for use, no waste is generated

4 Soil pollution D D N/A N/A Since this Project has the objective of irrigation water supply, no soil pollution is resulted from the work.

5 Noise / vibration

B- D B- N/A Under construction: Transport of materials by heavy machinery and trucks are made toward the sites. However, serious noise / vibration is not generate from these activities. However, consideration would be needed to pay when the pass in the living quarters.

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Evaluation at Scooping

Evaluation after the survey

No Environment Item Under constructio

n

During the use

Under constructi

on

During the use

Reason of judgment

During the use: Once offering for use, no noise/ vibration is emitted.

6 Land subsidence

D D N/A N/A Since no groundwater lifting is planned in this Project, no land subsidence is supposed.

7 Odor emission D D N/A N/A Since this Project has the objective of irrigation water supply, no cause of odor is resulted from the work.

8 River bottom state

B- C B- C Under construction: Though excavation in river-bed is accompanied with the construction work of the weir, the scale is very limited where the sediment deposit is very little. Almost no detrimental effect is resulted to water quality of the river. During the use: The extent of the protrusion from river bottom is very limited, without giving heavy impact on bottom regimenting or variation of river bed.

Natural environment

9 Eco-system, protection area

D D N/A N/A The sites of construction work in this project are not situated in any protection/ conservation area.

10 Hydrological phenomena

D C N/A C Under construction: Since the work in the river is carried out by partly closing the river-bed, the river discharge can directly release to the downstream as before. During the use: The planned quantity of intake is fairly little as compared to droughty water discharge, resulting in very limited impact on the river flow.

11 Topography/ geology

D D N/A N/A Under construction: No plan is included to collect large amount of stones, to excavate or fill large quantity of earth. Since the work is rehabilitating nature, no sizable variation is resulted in topographical and geologic situations of the area. During the use: Once offering for use, no impact on these factors arises

Social environment

12 Evacuation, removal of local population

D D N/A N/A Because the contents of construction in this project include rehabilitation of intake weir in torrential stream, the existing open canals and gates. The section to expand the width is located on public land owned by the government. Therefore, non-voluntary/ forcible removal of the inhabitants does not arise.

13 Vulnerable strata, ethnic minority, aboriginal tribe

D D N/A N/A Any aboriginal tribe or minor ethnic exists in the target Project area. Also, no impact thereon arises from activities of this Project.

14 Such local economy as employment and livelihood means

B+ A+ B+ B+ Under construction: Since hiring opportunities of local inhabitants are generated by the construction work, possibly beneficial impact on local economy is expected. During the use: O/M cost of the existing facilities is economized, increased crop production and subsequent livelihood improvement of farm households are expected accompanied with the improved water distribution service.

15 Water use B- D B- N/A Under construction: Accompanying with the new construction of weir, some impact by turbid water during the work may happen. During the use: Once offering for use, no impact on water use arises

16

Biased benefit and damage

D D N/A N/A Agricultural benefits arising from this Project are equitably distributed among all beneficially farmers. By this reason, no biased distribution of

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Evaluation at Scooping

Evaluation after the survey

No Environment Item Under constructio

n

During the use

Under constructi

on

During the use

Reason of judgment

distribution benefits and suffering is resulted from the Project.

17

Cultural heritages

D D N/A N/A No particular cultural heritage exists within the Project area. No possibility of impact of this Project on the local culture is conceivable.

18

Landscape B- C B- C Under construction: excavation is worked that has very limited extent but has more or less possibility of altering topographic appearance. During the use: Such artificial structures as weir body and revetment are considered to have some possibility of changing surrounding landscape.

19

Labor environment (including labor safety)

B- D B- N/A Under construction: Careful consideration on possible accident during construction is indispensable. During the use: Since facilities are rehabilitated, gate operation is made easier resulting in improved labor condition.

Others

20 Accident B- D B- N/A Under construction: Potential risk would arise from the Project such as possibility of traffic accidents caused by vehicles of the construction work giving damages to local inhabitants, those caused by heavy machinery during rehabilitation of open canals and gates etc. During the use: No impact on the ambient environment because of mere rehabilitation of the existing canals.

21

Territory transversal impact and risk of climatic variation

D D N/A N/A Taklai River over which the weir is installed is a tributary of Mao River flowing down to India, but no fluvial agreement has been concluded. Either, sizable change in the flow that can induce climatic variation is not evolved from this construction work.

Evaluation classes: A+ : Particularly positive impact is brought by the activity, A- : Particularly negative impact is brought by the activity, B+ : Positive impact is brought by the activity, B- : Negative impact is brought by the activity, C : The extent of the impact is unknown and D : No impact arises from the activity

1-5-4 Elaboration of impact-mitigating measures

As possible measures to alleviate and to avoid negative impacts likely to take place by the

implementation of this Project, the following countermeasures are considered necessary as tabulated

below. These impact alleviating or avoiding measures can be realized to put into practice within the

indirect cost included in the contract between Japanese government and constructors, thus no

additional cost is required for taking them. As concern monitoring, the contracted constructor monitors

the ambient environment impacts in compliance with the laws and regulations of Bhutan, then the

consultant engaged in this Project identifies the contents of the constructor’s report, the consultant

submits the report to Bhutan side, and then need to receive the approval by Bhutan side.

Almost no detrimental effect is resulted to Air pollution and Water pollution, and then those are not

included in the Monitoring plan.

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Table 1-16: Elaboration of negative impact alleviating measures

Negative impact Alleviating or avoiding measures

Monitoring plan Responsible Agency

【Air pollution】 Dust occurs during the passage of construction vehicles.

・ Water will be sprinkled on the road during construction works.

【Method】Whether proper / legal treatment or disposal is practiced or not is identified at the sites. 【 Period 】： Construction period 【Frequency】：once / month

Contractor DoA

【Wastes】 Excavated earth evolves from some construction work. In rehabilitating the existing canals, waste scrap pieces evolves.

・ As to the method of disposal of wastes, the standard of waste disposal/ treatment practiced in Bhutan is observed.

【Method】Whether proper / legal treatment or disposal is practiced or not is identified at the sites. 【 Period 】： Construction period 【Frequency】：once / month

Contractor DoA

【Noise/ vibration】 During construction work, Noise/ vibration evolve from operation of back-hoes and passage of trucks.

・ Construction machinery mounted with silencers and adequate mufflers are used to minimize noise emission.

・ In the sections where residence quarter is located, construction work at night is refrained.

【 Method 】 State of heavy machinery use is identified at the construction sites. ・ Hearing is held amidst

neighbors to Identify whether complaints are made. 【 Period 】： Construction period 【Frequency】：once / month

Contractor DoA

【 Hydrological phenomena】【water use】 Turbid water evolves during the excavation at river-bed.

・ Since the work in the river is carried out by partly closing the river-bed, the evolved turbid water can be treated in a sedimentation basin installed at downstream of the evolving sites.

【Method】Whether proper treatment is practiced or not is identified at the sites. 【 Period 】： Construction period 【Frequency】：once / month

Contractor DoA

【 Labor environment 】【Accident】 During construction work, traffic or site-work accidents may be caused.

・ Whether there is too tight operation schedule or not is identified.

・ Traffic control staff is placed along the construction roads.

・ The constructor explains contents of the work to the workers with necessary care taking for their safety to the laborers prior to the start of the work, and makes daily safety identification before the work.

【Method】Content, method, duration, area/ extent of the work, kind of mobilized construction machinery / vehicles are carefully identified. ・ Site traffic frequency

survey and hearing are conducted to ensure safety.

【 Period 】： Construction period 【Frequency】：once / month

Contractor DoA

1-5-5 Monitoring Plan and Environmental Checklist

The provision of monitoring plan and environment check list has been elaborated in DoA of ministry

of agriculture and forestry under the support by the staff of the Study Team in charge of environment

consideration. This item is included in the identification of the state of construction work, and

performed by the budget estimated as an item of indirect instruction cost. Environment monitoring is

to be made by the contracted constructor. Contractor should report to consultant, then consultant

should report to DoA at the periodical site check by DoA or meeting. The monitoring is conducted

monthly, while the report to JICA is carried out quarterly based on Minutes of Discussion on

Attachment-4.2 with the acceptance of reported by DoA. The way of information disclosure is

recommended to use the web site of Bhutan desirably in order to open the information widely

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1-5-6 Stakeholder’s Meeting

Necessity of environmental and social consideration for the present project is explained to

stakeholders including Geog and WUC.

1-5-7 Land acquisition and resettlement

Necessity of land acquisition and resettlement in the project is not required. In Bhutan, generally, in

case of requirement of land acquisition which is more than 5 acre per household, the government of

Bhutan pay the compensation for the land owner with alternate land. In case of the less 5 acre per

household, the government correspondingly pay the compensation

1-5-7-1 Necessity of land acquisition and resettlement

This matter nothing to do with project

1-5-7-2 Legal framework for land acquisition and resettlement

This matter nothing to do with project

1-5-7-3 The range of area for land acquisition and resettlement

This matter nothing to do with project

1-5-7-4 The detailed measurement for compensation and support

This matter nothing to do with project

1-5-7-5 The way of complaint management

This matter nothing to do with project

1-5-7-6 Implementation agency for the resettlement and responsibility

This matter nothing to do with project

1-5-7-7 Implementation schedule

This matter nothing to do with project

1-5-7-8 Finance and budget

This matter nothing to do with project

1-5-7-9 Monitoring and monitoring form by executive agency

This matter nothing to do with project

1-5-7-10 Meeting of residence

This matter nothing to do with project

1-5-8 Draft monitoring form

Attached on appendix-A6.8

1-5-9 Check list of environment

Attached on appendix-A6-8.

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Chapter 2 Contents of the Project

CHAPTER 2 CONTENTS OF THE PROJECT

2-1 Basic concept of the project

National Development Tenth Five-Year Plan (2008-2013) is a guiding plan of Bhutan related to this Project. From agricultural point of view, Ministry of Agriculture and Forests (MoAF) has provided strategic programs for strengthening markets, marketing and production of agricultural products for the purpose of ensuring food security and alleviating rural poverty. Concretely, 29 programs have been implemented through the initiative and in charge of MoAF, by which the following impacts are expected in terms of agriculture:

① Improving self-sufficiency ratio of rice from 50% to 59%,

② Increasing the level of annual farm-income from Nu10,700 to Nu35,000 and

③ Reducing the rate of local population stratum below poverty line from 30.9% to 20%.

Out of the above-described 29 programs, 7 projects have been proposed to improve environment and efficiency of water use/intake for irrigation water targeted in southern area of Bhutan, thereby expansion of dry-season irrigation has been expected. Taklai Irrigation Area is included in one of the target areas of these programs. “Contribution to the realization of double-cropping of rice in the target beneficiary area” is considered as the overall goal of this Project.

Also, as regards the Project purpose, it aims at “enabling to supply irrigation water to the initially targeted area planned in Taklai Irrigation System”. This system has the largest beneficiary area in irrigation projects in Bhutan (over 1,000 ha) and the only one nationally-managed project. This Project is expected to serve as a model scheme in Bhutan because synergetic effect can be realized between this Project and nationally implemented canal rehabilitation scheme by the reason that rehabilitation of existing canals has been implemented as a national strategy with the objective of expanding the scale of dry-season irrigation, thus enabling stable water supply throughout the year, thereby targeting to mitigate poverty rate and to promote higher farm income, also by the reason that larger scale of project output can be anticipated by its large impact since it has larger project area than the scale of perimeter in other district (about 200ha).

In order to fulfill the above-mentioned overall goal and the project purpose, it is indispensable to realize stable water intake and water supply with permanently functioning facilities in which climatic change (abnormal scale of flood etc) are taken into consideration in its design, and it is also essential to combine new-construction and rehabilitation of irrigation facilities by hard component with the capacity improvement of maintaining and managing them by soft component. The inputs, activities and outputs of this Project contain the following:

Required Inputs

1) Procurement of machinery/equipment and materials necessary for new-construction and rehabilitation of the facilities, implementation of the work,

2) Dispatching human resources (engineers) accompanied with the above-cited activities, and

3) Dispatching Japanese engineers to provide soft component.

Required Activities

1) Conducting study for detailed design required for the above-cited procurement and work,

2) Implementation of the soft component with regard to capacity improvement for operating and

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maintaining facilities.

Expected Outputs

1) Recovery of facility functions of Taklai Irrigation System as it has initially been planned,

2) Economization of operation and maintenance costs through the realization of proper water distribution by means of improved water management and optimization of operation and maintenance for the facilities.

2-2 Outline design of the requested Japanese assistance

2-2-1 Design policy

2-2-1-1 Basic policy

In formulating the Project, the position, the effects, technical and economic feasibility/ relevance of Japanese Grant Aid toward the implementation of this Project are to be verified, thereby essential and optimum design of the planned facilities is provided for obtaining proper fruit/ outputs of the Project.

Basic principles applied to the facility design include integrating the existing water-intake system of diverting water at two intakes at upstream (High Level Canal : H.L.C) and downstream (Low Level Canal : L.L.C) sites into an integrated head works (see the figure at lower right side), satisfying the capacity of the facility to convey planned water quantity by this integration, also repairing/ rehabilitating facilities of the existing irrigation system the irrigation functions of which have been damaged and deteriorated/ dilapidated.

In particular, the following three reasons are pointed out as the background of need of designing an integrated head works: 1. Since the existing two water-intakes follow gravitational intake with the intake facilities and the head race directly contacted with the stream flow that have frequently been damaged by floods, 2. expenditures at the scale of an annual average of 2.5MNu equivalent have continuously been incurred for the last 6 years only for repairing and maintaining the banks along the head race (especially heavy damages were brought in 2004 and 2010), 3. The degree of damages occurred at the banks of head race often reaches blockage of water flow that inhibits stable water intake, thus the elimination if these obstacles can be longed by the construction of the integrated head works.

The details of the design will be given below, but they are briefed here, to provide the structure of the integrated head works with sufficient strength that will be constructed at the upstream of the existing H.L.C intake with stabilized river-bed and that allows to take the totaled water quantity of both existing H.L.C and L.L.C sites. Irrigation water thus taken into the canal will be distributed at its existing downstream diversion points according to the water requirement for each irrigation area. The stable supply of irrigation water is pursued by estimating irrigation water requirement and flood discharges to be planned in the Project and strengthening a part of head race by newly constructing

Fig 2-1: Image of integrated intake

New

Headr

ace ca

nal

and

reha

bilita

tion of

exist

ingca

nal

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culvert structure with reinforced concrete that will be connected to the existing main canal at H.L.C site. At the same time, with a view to functional recovery of the irrigation system in this Project, the following are to be included in the work of the Project based on the contents of the request by the Royal Government of Bhutan and on the result of the study.

Table 2-1: Target component（Comparison between Report and Request letter） Expression by Report Expression by request letter（Refer

to :Attachment/Annex-3） ① Construction of integrated head works 1) Construction of a permanent headwork at High

Level canal Intake ② Rehabilitation of head race and construction of sedimentation pond,

2) Construction of flood protection structures near the High Level and 5) Construction of a sedimentation tank / desilting chamber at High Level Canal

③ Raised up of link canal and rehabilitation of its terminal part

3) Expansion of High Level canal and Link Canal between High Level and Low Level Canal

④ Construction of flood control work at the confluence work to merge the link canal into L.L.C

4) Construction of protection structures near the confluence of Low Level Canal and link Canal

⑤ Raised up of the H.L.C and repairing its damaged part 3) Expansion of High Level canal and Link Canal between High Level and Low Level Canal

⑥ Rehabilitation of siphon in the H.L.C part of the main canal (implementing protection work for exposed part of siphon pipe and repairing damaged part)

6) Rehabilitation of siphons along main canals

⑦ Renewal of the damaged or deteriorated gates installed on the H.L.C and L.L.C

7) Rehabilitation of old gates along main canals

⑧ Installation of water gauge facility at the integrated head works,

8) Installation of river gauging station at High Level head works for flow measurement

⑨ Construction of protection dike at downstream of Taklai River for the purpose of protecting farmland and canals during floods, and

5. Protection works for farm land in the irrigation area against floods

⑩ Implementation of soft component on water management and operation/ maintenance for the facilities

5. Soft component on operation and maintenance of the new irrigation system

The figure below shows the site of the above-mentioned construction works.

Fig 2-2: Location map of the cooperation Project

2-3

2-2-1-2 Policies applied to natural/ environmental conditions

The following principles are applied to natural and environmental conditions necessary for formulating the facility construction plan.

(1) Flood discharge

1,710m3/s is adopted as the design discharge that has been calculated from 1/50 year’s probable rainfall which based on the record at Bhur Observatory Station. In this regard, this value is larger than the maximum recorded flood discharge in the past estimated from the observed flood vestiges.

(2) Drought discharge

Annually probable discharge at the site of the planned head works is estimated at around 1.12m3/s from the observation result available in and around the site. Since this value is evidently lower than design irrigation water requirement, 2.24m3/s as shown below, it is considered possible that in the course of probability evaluation drought discharge corresponded to 50% of the design water requirement appear every year.

Yet, a discharge of about 3.8m3/s has been observed at the planned site of the head works during the study team was in February, or during dry season, and the interviewed persons in this study told that such a level of discharge as observed during the study was seen every year in the interview survey.

Considering these situations, each facility is designed based on 2.24m3/s, required irrigation water quantity, however, taking account of some possibility of evolving water-deficit years failing to satisfy the planned water supply, such practices as rotational irrigation and time-limited irrigation covering all blocks in a day is planned to cope with such possibility.

(3) Geology at the planned site of head works

Geological formation in and around the planned site of head works can roughly be classified into gravel and pebbles over the stream-bed and quartzite / gneissic boulder derived from volcanic origin materials judging from the result of a geologic survey. Both of these strata are relatively compact judging from the measurement results with 35° or larger for their internal friction angle and about 2.0tf/m3 as unit weight.

The Strata at planned site is composed of gravel and pebbles mainly. therefore it is difficult to execute the SPT (Standard Penetration Test) to understand the durability of foundation such as by the N value. However there is no settlement strata to be predicted, because the such as clay stratum could not find by boring survey. On the other hand, the internal friction is identified as 35 degree at stratum around below EL 298 which is understood as tight gravel and pebbles stratum. Accordingly, the structure foundation level is deeper than EL 298.

Therefore, it is considered feasible to adopt this site as the foundation of the planned head works by subject to be removed the mobile river-bed gravel. And an apron of head works is designed as floating type because the foundation is conceived high permeable strata. The following table gives parameters of basement clarified by the geological survey.

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2-2-1-3 Farming and irrigational (on-farm) conditions

As this Project has main objective of functional recovery for Taklai Irrigation System through new construction of integrated head works and head race as well as rehabilitation of main canal and appurtenant structures etc, farming environment of the beneficial farmers will be improved as a result of enabling stable supply of irrigation water. Thus, expansion of irrigation area that leads to increasing crop production is anticipated, further this improved irrigation will enable to realize spring cropping (dry-season farming) that is rarely practiced at present. In such a way, shifting to double-cropping probably induces a transformation in cropping pattern.

As far as crop selection has basically been kept at farmer’s own disposal without any policy intervention, it is predicted that some farmers surely try to be engaged in spring crops (dry-season cropping) with paddy and wheat once stable supply of irrigation water is realized. Research and Development Center (RDC) takes charge of research and development including formulation of year-round farming plan in conjugation with the alteration in cropping pattern, selection of paddy varieties, cropping technology and post-harvest practices while Dzongkhag Agriculture Sector (DAS) are responsible for extension activities, thus supporting beneficiary farmers.

No radical change is brought in the operation and maintenance of terminal irrigation facilities and sharing system of water management (operation of water-gates), and RDC and Central Machinery Unit (CMU) (only on major damage) are in charge of controlling basic facilities (from head works to main canal) while Water Users Associations (WUA) takes responsibility of operating and maintaining secondary canals up to terminal facilities. As regards operation of water-gates, water guards selected and appointed by WUA are responsible for them.

2-2-1-4 Policies applied to socio-economic situations

It is considered that the rehabilitation of Taklai Irrigation System and subsequent improvement in farming conditions contribute to beneficiary farmer’s increased food production and their livelihood improvement, leading to favorable impact to local economy. Fortunately, no cases of land-use system in which only a part of farmers hold large tract of farmland obtaining biased benefits are observed in Taklai irrigation area, so it is forecast that this Project gives equal benefits to as many beneficial farm households as possible.

In so far as this Project has the objective of rehabilitating the existing Taklai Irrigation System, it won’t bring any new large-scaled development in the area. It follows that living customs and traditions of the beneficiaries will be conserved as they are now.

Further, from gender point of view, men and women used to share farm labor/ practices within household or community, hence it is considered that expansion of cropping area would not result in an

Table 2-2: Basement parameters of the basement at the planned site of the head works

Sourced by of Geological Survey Report

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increased burden for women only.

2-2-1-5 Policies on the situations of construction / procurement

(1) Laws and regulations to be pursued

As to labor conditions including minimum rate of wages and labor hours, they are based on the articles described in Labor Standardization Law in Bhutan.

(2) Standard norms to be observed

Because standards of construction/ design management in terms of construction work have not yet been consolidated in Bhutan except for some particular fields (road), specifications, quality/ testing control of machinery/ equipment procurement and construction work are to be founded on norms of ISO and JIS.

(3) Construction situations

Currently, local contractors managed by local population are found in Bhutan, but no construction firm has ever been established by foreign capitals. As to local constructors, most of them have small scale but some of large-scaled construction agents develop their activities in and around the capital Thimphu, holding a lot of construction machinery. Their major performances only include road construction, protective embankment work with wet masonry, gabion etc, with only poor performances in the construction of concrete structures. Under such circumstances, during the construction work of this Project, it is expected to utilize local constructors in a part of the work including wet masonry and gabion layers in order to secure the completion of the work within the contracted period. Because Japanese contractor have responsibility for quality control for entire construction including other works and Japanese consultant check it, it’s believe to be able to secure quality and the completion of the work within the contracted period .

(4) Procurement situations

The study on the availability of local construction firms has revealed that both labor force and construction materials (especially aggregates for concrete) have been in short of their demands in Bhutan, affected by nation-wide including Gelephu housing construction-rush construction of air-port, hydro-power generation dams etc, and this shortage has led to price escalation of unit labor wage and unit costs of materials, and it is said that construction costs have been increased for the last couple of years. Therefore, in this project, it is planned to manufacture aggregates for concrete at the site by crusher plant and to employ Indian labor when it is difficult to get Bhutanese labor force.

2-2-1-6 Policies on the utilization of local constructors (construction firms)

In the cases of work including wet masonry / gabion, it is possible to make use of local constructors taking its scale and degree of difficulty into consideration.

2-2-1-7 Policies towards management and operation/ maintenance

The system for the management and operation/ maintenance of this Project has already been established without any particular problem. However, it is necessary to improve the capacity of operation and maintenance accompanying with the newly constructed and rehabilitated facilities considering the following conditions:

・Because no permanent facility exists that doesn’t need any maintenance / management, operation and maintenance techniques should be mastered with the preventive and conservative ideas in

2-6

order to keep as long life as possible of the facilities that are newly constructed or rehabilitated by this Project,

・Pertinent method of water management (operation of gates) should be trained in order to make improved capacity of the facilities fully functioning.

A soft component is provided for realizing these capacity improvement targets as a supporting activity, thus assisting to obtain required knowledge and techniques and to sustain operation and maintenance.

2-2-1-8 Policies on the establishment of the grade of the planned facilities

The facilities of Taklai Irrigation System shall be designed by adopting the following parameters, based on natural and environmental conditions and the planned scale of the target area:

・Design water intake: 2.24 m3/s （maximum intake quantity）

・Design flood discharge: 1,710 m3/s（probable flood discharge of once in 50 years; 1/50）

The planned facilities are mainly those constructed inside the river and outside it. Since Taklai River is characterized by its steep river-bed gradient（I=1/60）with scattered boulder over the river-bed, risk that facilities installed inside the river-bed are damaged by abrasion and impact with bounding bolder is fully taken into account. Also, as the planned flood discharge, 1,710 m3/s shows a higher ranked parameter among torrential valley streams, it is required to design structures with sufficient stability against enormous flood energy considering the above-cited character of the target stream that has very narrow section of stream flow.

However, Based on the Taklai river that facilities should be planned under hard natural conditions as observed in this case, it is considered relevant from the economic point of view to allow some degree of possible damages to such extent that it will not reach to a serious damage by mitigating the natural action, rather than directly resisting against evolving natural forces, What is important is the establishment of proper and regular maintenance to sustain the project facilities over a long period of time instead of providing excessive or large- scale of facilities.

For the facilities to be constructed outside of the river such as canal, the same policy is applied to repair and rehabilitation works, considering that the possibility of proper maintenance by Bhutanese can lead to long-term operation of functions of the facilities

In conclusion, in the facility planning, structures are designed with sufficient durability by assessing the influences of floods and bounding boulder and permitting some degree of damages, whereas by coping with these damages by proper maintenance, also adopting the grade of the planned facilities by assessing shapes of the structures so that it can alleviate the action force of flood energy or impact of boulder.

2-2-1-9 Policies concerning work method/ procurement method and construction period

(1) Construction work of the Taklai Irrigating System

In this Project, the construction work consists of that inside the stream including integrated head works, head race, existing embankment protection reinforced with layer of gabion, downstream embankment etc and that outside the stream including link canal, high level main canal and low level one (including the confluence work) etc.

In the first dry season, procurement and setting for batcher plant and crusher plant will be carried out until February of the first dry season. Considering not entering flooding period under construction of

2-7

the river structures, constructions of downstream embankment, link canal, high level main canal and low level one can be completed within dry season are planned.

In the second dry season, the order of the construction of integrated head works, head race, and existing embankment protection reinforced with layer of gabion is planned as a rule completing construction until May within dry season.

Casting by crane is to be adopted for casting concrete in constructing the integrated head works that have broader section and require large volume of concrete, considering its workability, but for the work with smaller section, manual casting is planned.

Construction of the integrated head works belongs to the work inside the stream. Because the construction site of this facility is surrounded by mountains, it is difficult to construct it in the lump with a temporary diversion of the entire stream. For this reason, the construction of this facility is designed by the method of partial coffer controlling half of the river flow with large sized sand-bags. Water entering/ emerging the coffer will be drained by pumps.

Construction of integrated head works and head race produces large volume of excavated earth, but it can be carried by dump-trucks and spread over the river-bed in front of the existing protecting gabion layer located at the downstream and right side river bank near the construction site. The location of the spoil bank has already been consulted and agreed with the counterpart agency.

Also, during the period of constructing two bridges traversing the high level main canal, a detour route is to be constructed near the construction site so that the work does not hinder passage of local inhabitants or traffic of vehicles.

(2) Method of procurement

Steel rods, sand, gravel, stone etc that are marketed in Bhutan will be locally procured for use in this Project. Conventional construction machinery such as back-hoes, bulldozers, damp-trucks etc are also locally available in Bhutan. Because of cement, rough terrain, concrete mixer car and various kinds of plants are not available in Bhutan, they will be procured in the third country (India) to be used in this Project.

(3) Determination of construction period

Construction period is to be determined examining the following conditions:

・ Access route to the Project site passes through various points over the stream and traffic during rainy season is blocked on these points. The construction period is therefore set during a dry season that begins in October and ends in May next year.

・ Because the entire volume of concrete to be cast amounts to around 10,000m3, it has been found difficult to complete the casting within a dry season. Hence, the construction work requires two dry seasons. A policy has to be regarded so as to complete casting of as much concrete as possible in the 1st year dry season so that completion of the entire work can be secured till April of the 2nd dry season.

・ Capacity of casting concrete is estimated at 50m3/day in the case of casting by crane, and 17.5m3/day by manual casting by a team. The casting rate is targeted at about 85m3/day.

2-2-2 Basic plan (Construction plan/Equipment plan)

2-2-2-1 Design irrigation water requirement

2-8

Design irrigation water requirement is calculated from the beneficiary area measured in the site study and by means of several dimensions required for planning irrigation. It can be obtained as a product of unit water requirement and the area of targeted perimeter.

Q = q・A

where Q: design water requirement (m3/s) Q1(beneficiary fed from H.L.C) + Q2(beneficiary fed from L.L.C) q: unit water requirement (m3/s/ha) A: design irrigation area (ha) A1(beneficiary fed from H.L.C) + A2(beneficiary fed from L.L.C)

In this equation, the unit water requirement can be derived from both water-duty in depth and irrigation efficiency as follows;

q = D×1/1000×10,000/86,400/K

where D: water duty in depth (mm/day)、K: irrigation efficiency

The water duty in depth (D) is susceptible to the soil conditions in the target area where loamy sand soils are distributed and judged as soils with intermediate character between dry paddy field (D=20mm) and wet paddy field (D=10mm) in Japanese classification term where the optimum duty is considered as D=15mm. In this context, D=15mm is also defined as optimal in the irrigation planning manual in Bhutan.

As to irrigation efficiency (K), most parts of both main canal and branch canals have already been lined (by wet masonry) and water leakage from the entire canal is limited except for some area-confined cases, thus conveyance loss has been estimated at 15%, then the efficiency is defined as K=0.85 (1－0.15).

From this result, unit water requirement is calculated at q = 15×1/1000×10,000/86,400/0.85=0.002 m3/s/ha (2.0 /s/ha). As shown below, this value is not so much different from those measured in ordinary locations in Japan and other project areas in Southeast Asian region measured in recent years, and judged within the compatible range.

Table 2-3: Policy of foreign unit water requirement

Country (field) Japan (dry paddy) Japan (wet paddy) Viet Nam (Central) East Timor

Water duty: D(mm) 20 10 11 7.5

Irrigation efficiency: K 0.85 0.85 0.75 0.75

Unit Water Requirement: q(l/s/ha) 2.7 1.4 1.7 1.2

On the other hand, as for design irrigation area, through the comparison of the area of settlement as of original design of Taklai Irrigation System（1,445ha）with the measured area by the newest edition of satellite imageries（1,340ha）93% has been obtained in total of the beneficiary area, as tabulated below, and this level is considered as a reasonable value taking into account the other areas of land use including housing area, roads and waterways etc. In this regard, the fact that the beneficiary area fed by the Low Level Canal has greatly decreased to 68% raises an issue of detrimental effect of farmland erosion caused by recent floods, implicating the importance of embankment protection along the stream.

The area given above also includes a part that has higher altitude area than the defined High Level Canal. Since it can be judged that future feasibility of the pump irrigation is deemed low from the

2-9

view point of cost-effectiveness, only the perimeter under gravitational irrigation is counted as the design target irrigation area, namely 1,120ha.

Table 2-4: Design irrigation area by target canal

Canal feeding the areaSettlement area(ha)

①

Measured area (ha) ②

Area ratio ②／①

Design irrigation area (ha)

Remarks

High level canal (H1) 770 880 114% - Including irrigation area higher than canal E.L

High level canal (H2) (550) (660) 120% 660 Target area covered only by gravitational irrigation

Low level canal (L) 675 460 68% 460 The same as above

Total (H1)+(L)=1,445 (H1)+(L)=1,340 93% 1,120

From the above given results, design water requirement and water intake quantity are derived as following in the summary table and in the figure of canal network diagram.

Table 2-5: Design water requirement and design maximum water intake

Item High level canal Low level canal (link canal)

Maximum design water intake quantity Remarks

Unit water requirement q(m3/s/ha) 0.002 0.002 0.002

Design irrigation area A (ha) 660 460 1,120

Design water requirementQ(m3/s) 1.32 0.92 2.24

Figure 2-3: Canal network diagram

In this concern, it is also conceivable that minimum flow of Taklai River in dry season (defined as the minimum discharge during dry season) may become lower than the design water intake. In this case, it will be necessary to make effort of minimizing the volume of water use by such practices as rotational irrigation and time-limited irrigation covering all blocks in a day.

2-2-2-2 Design of the integrated head works

As shown above in the basic principles, water intake facilities constructed in Taklai River for the purpose of fulfilling a stable water supply is designed as the integrated head works in Taklai River by amalgamating the existing high level intake and also low level intake into unified one.

2-2-2-2-1 Location of the integrated head works

Streams with a steep gradient（I=1/60）of river-bed, also with a lot of bounding boulder as observed in this river are classified into torrential river. In the cases where a location of headwork is selected in such torrential river, the design of head works should be considered as follows; to locate at stable

A=1,120(ha)

Q=2.24(m3/s)

A=660(ha)

Q=1.32(m3/s)

A=460(ha) Q=0.92(m3/s)

A=460(ha)

Q=0.92(m3/s)

Newly constructed integrated head works

High level canal

Low level canal

Link canal

Existing

Low level intake

2-10

stream, to avoid the sites where sedimentation readily takes place due to a suddenly widened river-bed, to be possibility of construction with cheaper cost etc.

The candidate sites of constructing the integrated head works have been focused on the location of the existing intake attaching importance on the readiness of connecting to the existing head race, then 3 candidate sites have been proposed as shown in the follows figure below in the result of site survey.

In this context, possibility of selecting the location at further upstream of the site A has been judged improper because there are numerous numbers of scattered larger sized boulders with unfavorable conditions for the construction

As a result of the evaluation through the site survey on topography, condition of river-bed material composition and connectivity to the existing canal, comparative construction cost etc, it has been judged that the "Site A" turns out to be the most appropriate location for its construction.

Table 2-6: Selection of the location for the construction of the head works

Candidate location of constructing head works

・Location adjacent to the existing intake

Candidate Site A Site B Site C

Topographic conditions

The big rocks is exposed in the right bank. It can partly be excavated to unify with the body of head works’ structures to make workability and stability more favorable. Because of narrower stream width, smaller sized facility can be constructed than any other site. Velocity of the stream flow is more rapid than that of other sections located at downstream side.

（○）

This site is located at a position where the velocity of the flood flow becomes slower after passing a meandering part. Hence, flow velocity of flood is decreased as compared with that in Site A. Owing to wider stream width than that of Site A, larger-sized structure of weir would be considered

（△）

This site has the same characteristics as those observed in Site B.

（△）

River-bed conditions

Averaged size of diameter of sand and gravel was measured at 7cm in a simple measurement survey of river-bed materials, but the bounding stone with the diameter over 50cm are comparatively observed at here. Judging from the above-cited tendency, velocity of the stream flow is faster, it make larger-sized bolder sediment easier Therefore, it can be concluded that stable water way is not easily changed by small-sized

Averaged size of diameter of sand and gravel was measured at about 5cm by the result of simple measurement survey of river-bed materials, but the bounding stones with the diameter ranging 50cm~20cm were comparatively observed. The sizes of these are found smaller than those found in the Site A. judging from the above-cited tendency, sedimentation with smaller diameter are easy

This site has the same characteristics as those observed in Site B.

(Existing head works)

Site B

Site C

(Existing head race)

Approx. 200m

Taklai river Flow

Approx. 200m

Site A (adopted)

2-11

flood flow.

（○）

because the flow velocity is slower than that of the Site A. Though the sedimentation is also influenced by the condition of supply of sand and stones from the upstream side, the river-bed seems to be more easily shifted as compared with the Site A.

（△）

（△）

Water-intake conditions

Since the height of the river-bed is almost the same as that of the existing bed level of the head race, the height of back-water rising at the head works can be minimized. Since the narrow stream width, water can easily be caught.

（○）

The elevation of the river-bed is lower than that of the existing bed level of the head race, leading to the necessity of fairly high back-water rising by about 2meter at the head works.

（△）

Current elevation of the river-bed is further lower than that of the Site B, it becomes necessary to raise the back water level by about 4 meter at the head works.

（△）

Construction conditions

Since it is possible to make the width and height of the weir smaller size owing to the proper topographic and water intake conditions, the construction cost can be economized than other site.

（○）

Due to improper topographic and water intake conditions, wider weir with higher height and longer apron is needed, thus leading to higher construction cost as compared to the Site A.

（×）

Due to improper topographic and water intake conditions, a widest weir with highest height and longer apron is needed, thus leading the construction cost highest of the three candidate sites.

（×）

Stability against flood energy

Though this site is located at the location where flow velocity becomes rapid by topographic condition, in order to reduce the effect to the stream section can be minimized by making the height of the weir as low as possible, thus attenuating the impact of flood attack.

（○）

Though this site is located at a position where flow velocity becomes slower by its topographic condition, necessity arises to construction of higher weir, leading to disturbing of river flow, thus impacts of floods and bounding stones are considered to be greater.

（×）

Though this site is located at a position where flow velocity becomes slower by its topographic condition, it is necessary of the height of the weir. This gives a severe effect to river flow, leading to larger impacts by the floods and bounding stones.

（×）

Integrated evaluation

The scale of the facility can be made smallest among three candidate sites, and the highest water intake function can be expected. the construction cost is estimated at the lowest among these three sites. Though the site is located at the position where flood power is assumed strong, attenuation of the impact is possible by minimizing the scale of the structure.

○ （adopted location）

In this site, the scale of the structure is ranked at the second among three candidate sites. Though this site is located at a position where the flood impact can be weakened as compared to the Site A, higher rising of back water is required in order to secure the planned intake water. Thus, structure lead higher effect at flood than Site A. In addition, sand would more readily be sediment, due to the outlet out of narrow width

×

The scale of the structure in this site is largest among the 3 candidate. Though this site is located at a position where the flood impact can be weakened as compared to the Site A, higher rising of back water is required in order to secure the planned intake water. Thus, structure lead higher effect at flood than Site A. In addition, sand would more readily be sediment, due to the outlet out of narrow width

×

2-2-2-2-2 Type of the integrated head works

According to “The Standard criteria : Design of Head works in Japan”, the head works to be installed in torrential streams are roughly classified into 5 types, namely, gravitational/ natural intake type, diversion weir with sluice gate type, water cushion type, bar-screen (type of intake by underneath bar-screen, type of intake by the rear of bar-screen) and diversion weir with over-flow type guiding circle-arch face. Since among these, type of natural intake is the same type as it is currently used, and excluded from the examining evaluation while characteristics of other four types are compared and examined as shown tin the following table.

In evaluating for adaptability to the target river flow and intake function points of view, it is recommended to adopt the type of bar-screen is judged from durability against flood energy and stability of water intake for the available to highly variable discharge.

In this context, two types of bar-screen are applicable, namely, fixing bar-screen on the slope of the fixed weir or fixing it at the crest of the fixed weir. As a result of examining these from the standpoint of ease of water intake and effective use of water-head and also taking account of the scale of designed facility (collecting channel must be deepened, if bar screen is at slope of weir), the type of fixing the bar-screen at the crest of the weir is adopted.

2-12

Tab

le 2

-7: T

ype

s of

hea

d w

ork

s a

nd e

xam

ina

tion

of

wa

ter

inta

ke m

eth

od

Type

of w

eir

dive

rsio

n w

eir

Wat

er c

ussi

on

Bar

-scr

een,

wat

er in

take

un

dern

eath

the

scre

en

Bar

-scr

een,

wat

er in

take

at

the

rear

of t

he s

cree

n D

iver

sion

wea

r with

ove

r-flo

w a

t gu

idin

g ci

rcle

-arc

h fa

ce

St

ruct

ure

W

ater

inta

ke b

y in

stal

ling

a fix

ed w

eir

with

slu

ice

gate

to

orde

r to

mak

e ba

ck

wat

er

W

ater

inta

ke b

y in

stal

ling

a fix

ed w

eir

and

also

in

stal

ling

wat

er

cush

ion

unde

rnea

th th

e w

ater

dro

p

Wat

er in

let

is in

stal

led

at th

e si

de o

f the

wei

r.

W

ater

inta

ke b

y in

stal

ling

an o

verfl

ow

wei

r tra

vers

ing

the

stre

am

and

by

inst

allin

g ba

r-scr

een

at t

he t

op o

f cr

est.

Wat

er i

s co

llect

ed t

hrou

gh b

ar-s

cree

n in

to c

olle

ctin

g ch

anne

l.

T

he s

truct

ure

is s

imila

r to

the

typ

e sh

own

in

the

left,

bu

t th

e sc

reen

is

in

stal

led

at th

e sl

ope

of th

e cr

est.

Si

nce

inta

ke

quan

tity

is

as

larg

e as

ab

out

2.2m

3 /s a

nd w

ater

sho

uld

be c

olle

cted

by

wat

er-c

ushi

on

stru

ctur

e at

th

e do

wns

tream

to s

ecur

e th

e qu

antit

y.

W

ater

inta

ke b

y in

stal

ling

an o

verfl

ow

wei

r and

sha

ping

an

arch

of c

ircle

at t

he

over

flow

edg

e. W

ater

dro

ppin

g fro

m th

e ci

rcle

-edg

e is

into

the

colle

ctin

g ch

anne

l w

hich

is

inst

alle

d be

neat

h th

e ar

ch o

f ci

rcle

edg

e.

Adv

anta

ges

Th

is t

ype

can

colle

ct r

equi

red

wat

er

quan

tity,

can

keep

re

quire

d w

ater

in

co

nfor

mity

with

the

sca

le o

f irr

igat

ion

bene

ficia

ry.

th

e se

dim

enta

tion

can

be

redu

ced

by

the

flash

op

erat

ion

with

sl

uice

gat

e.

T

his

type

can

rel

ativ

ely

less

en t

he

quan

tity

of m

ixin

g sa

nd a

t its

inta

ke.

This

ty

pe

can

keep

th

e re

quire

d qu

antit

y of

wat

er i

ntak

e in

acc

orda

nce

with

the

scal

e of

the

bene

ficia

ry a

rea

Sinc

e th

e flo

od e

ffect

to w

eir i

s re

duce

d,

stab

ility

of th

e fa

cilit

y is

exp

ecte

d.

Th

e st

ruct

ural

adv

anta

ges

are

sim

ilar

to t

he t

ype

show

n in

the

left.

Sin

ce t

he

scre

en i

s in

stal

led

on t

he s

lope

of

the

wei

r, th

e sc

ale

of d

amag

es to

the

scre

en

can

be a

llevi

ated

.

S

ince

the

ove

rflow

ing

edge

has

a

shap

e of

arc

h, a

cen

trifu

gal f

orce

evo

lves

w

hen

wat

er

over

flow

s it,

th

us

it is

po

ssib

le to

mak

e le

ss le

ssen

the

degr

ee

of m

ixin

g sa

nd in

div

erte

d w

ater

.

Dis

adva

ntag

es

D

amag

es to

slu

ice

gate

s by

floo

d ar

e as

sum

ed

in

the

loca

tions

w

ith

high

er

flood

im

pact

, an

d al

so t

he s

truct

ure

is co

ncer

ned

dam

age

by

the

stru

ctur

al

dist

urba

nce

caus

ed b

y w

eir-u

p he

ight

Wat

er

inta

ke

beco

mes

im

poss

ible

on

ce s

tone

s an

d pe

bble

are

sed

imen

t on

the

wat

er c

ushi

on.

In

the

con

ditio

n of

th

is r

iver

tha

t flo

od d

isch

arge

per

uni

t w

idth

is

larg

e, t

he i

nsta

llatio

n of

thi

s st

ruct

ure

grea

tly d

istu

rbs

wat

er fl

ow, a

s a

resu

lt of

it,

le

ad

to

high

er

risk

of

dam

ages

to th

e st

ruct

ure.

S

ince

it is

inev

itabl

e to

mix

ing

of s

and

into

col

lect

ed w

ater

thr

ough

bar

-scr

een,

ne

cess

ity

som

etim

es

aris

es

to

inst

all

sedi

men

tatio

n po

nd.

The

mai

nten

ance

of

bar

-scr

een

is r

equi

red

to r

emov

e th

e cl

oggi

ng b

y sm

all b

olde

r.

P

ositi

on o

f co

llect

ing

chan

nel

in t

his

type

is

low

ered

as

com

pare

d w

ith t

he

type

sho

wn

in t

he le

ft ty

pe,

resu

lting

in

larg

er lo

ss o

f he

ad,

due

to t

he lo

wer

ed

heig

ht.

Th

e lo

wer

the

pos

ition

of

the

colle

ctin

g ch

anne

l is

, th

e th

icke

r th

e ap

ron

beco

mes

, le

adin

g to

hi

gher

co

nstru

ctio

n co

st.

Sinc

e th

e flo

od

disc

harg

e of

thi

s st

ream

is

huge

, hi

gh

prob

abilit

y of

dam

ages

to

the

part

of

wat

er c

ushi

on is

con

cern

ed.

In

this

ty

pe

of

wei

r, w

ater

in

take

qu

antit

y by

thi

s ty

pe is

lim

ited（

to le

ss

than

1m

3 /s）

The

cent

rifug

al

forc

e be

com

es

larg

er

as

stre

am

disc

harg

e in

crea

ses

and

flow

ve

loci

ty

is

acce

lera

ted,

so

wat

er in

take

itse

lf is

als

o lim

ited.

Eval

uatio

n on

th

e ad

apta

bilit

y to

th

e ta

rget

st

ream

an

d w

ater

in

take

fu

nctio

n

Sinc

e pa

rt of

flo

w

dist

urba

nce

incr

ease

s at

the

stre

am s

ectio

n un

der

the

cond

ition

that

eno

rmou

s flo

od e

nerg

y w

ith b

ound

ing

of s

tone

s an

d bo

ulde

r, fa

irly

larg

e st

reng

th is

nec

essa

ry fo

r th

e in

stal

led

stru

ctur

e.

This

typ

e is

not

so

adap

tabl

e to

this

stre

am.

Sedi

men

tatio

n of

St

one/

pe

bble

de

posi

t on

w

ater

cu

shio

n is

fu

lly

assu

mne

d, a

nd b

ecau

se e

limin

atio

n of

la

rge

ston

es a

re d

iffic

ult,

the

func

tion

of

wat

er

inta

ke

hind

ranc

e re

adily

ta

kes

plac

e.

Sin

ce th

e di

stur

bed

surfa

ce fl

ow

by

wat

er

cush

ion

durin

g flo

ods

give

s hi

gh r

isk

of d

amag

es t

o th

e st

ruct

ure.

Th

is ty

pe d

oes

not f

it to

this

stre

am.

T

he s

tabi

lity

of t

he f

acilit

y is

hig

h co

nfid

ence

be

caus

e of

th

e sm

alle

st

degr

ee

of

dist

urba

nce

to

the

stre

am

sect

ion.

Yet

, it

is s

till

nece

ssar

y to

re

info

rce

the

stru

ctur

e ag

ains

t the

hitt

ing

of

boun

ding

st

ones

.

Th

ough

m

aint

enan

ce

and

man

agem

ent

is

esse

ntia

l, st

abilit

y of

wat

er in

take

can

be

sust

aine

d.

S

and

mix

ing

is n

ot a

void

able

in

the

case

of

ba

r-scr

een

type

w

eir.

In

parti

cula

r, Th

is t

ype

has

low

er c

apac

ity

type

sho

wn

in th

e le

ft in

the

view

poi

nt o

f ef

fect

ive

use

of w

ater

hea

d, a

nd a

lso

the

cons

truct

ion

cost

is

conc

erne

d.

This

ty

pe d

oes

not e

xact

ly fi

t to

this

stre

am.

S

ince

int

ake

quan

tity

is s

truct

ural

ly

limite

d,

this

ty

pe

cann

ot

secu

re

the

desi

gn

inta

ke

quan

tity.

Beca

use

flow

ve

loci

ty in

crea

ses

durin

g ra

iny

seas

on, i

t m

akes

wat

er in

take

diff

icul

t.

Thi

s ty

pe

does

t not

fit t

o th

is s

tream

.

Judg

men

t △

×

○

△

×

2-13

2-2-2-2-3. Examination on the elevation of major parts of structures

(1) The crest of the weir

The water collecting channel is placed at the crest of the weir in the type of intake underneath

bar-screen to be adopted in the facility plan. Therefore it is designed to avoid mixing of mud/ sand

during water intake, and also to make less the effect of disturbance during floods as far as possible. In

order to avoid disturbing effect during floods, it is better to make the elevation of the weir crest as

close to the river-bed as possible, however, it become concerned about the mixing sand into the intake

water thus, it becomes necessary to keep the weir crest higher to some extent than the elevation of the

river-bed.

At the planned site has a

topography shown in the

right figure, the feature of

site is indicates outcrops at

the right bank and in the left

is seen the shallow sand

bank. The elevation of the

weir crest is determined by

this observation on the elevation of sand bank. Hence, the elevation of the weir crest is designed at EL

301.5m.

(2) The weir body

The elevation of the surface of the apron of weir is determined at EL 300.5m, around the same

elevation of the current river-bed, in order to avoid giving excessive impact to the weir by flood.

The elevation of foundation of the

weir body is to be judged by the

geological survey. The result of

this survey indicates that overall

geological feature in the planned

site are considered as those in

which stone/bolder and pebble

have been settled. Particularly,

according to the state of core

samples collected from the current

river-bed by a boring survey, small

and medium sized stone/boulder

and pebble are observed ranging

the depth of EL 299~ about EL 298m, and below these depth relatively larger sized stone/bolder and

pebble predominate is considered as the principle composition by the core samples, in addition these

strata are observed having compacted density. Therefore, the elevation of footing of weir body is

Fig 2-4: Transversal cross section of planned site

Fig 2-5: Profile of downstream side

Planned site of Head works

約110m

EL 298m~297m

changingpoint of riverbed by hugestone

FLOW

V=1:150H=1:1,500

Assumeddescended bedlevel (1/60)

Level of embedded foundationEL 297.5

2-14

determined at EL 298m.

In this connection, it was found that around 110m downstream from the planned site of head works,

the river-bed consists of huge stones with their diameter of 1m or larger, and this point is considered as

a turning point to a different bed profile. In other words, it is considered as keystone and the stability

of the river-bed has been kept by these stones.

Though it is difficult to evaluate the stability of these huge stones on river bed, but once the stability of

huge stones happens to be lost, the river bed at the upstream side begins to be lower elevation then the

gradient of the river-bed approaches to the mean river-bed gradient（I=1/60）, eventually until the

downstream of the river bed reach to EL 298 ~297m

Taking such observation of river-bed, it is designed that embedded foundation is installed at the rear

apron in order to secure the stability of the weir body and apron even if river-bed scouring takes place.

In this case, the elevation of the bottom of the embedded foundation is almost same the elevation at

the turning point of river-bed located at the downstream, namely, EL 297.5m.

(3) Elevation at the bottom of bed-protection

Bed protection work serves as the preventive measures against scouring evolved at the downstream of

apron. On the other hand, it has another objective of preventing extreme deformation of river-bed by

gently following gradual river-bed variation. Accordingly, the bed protection work is designed in a

form similar to the current shape of the river-bed. Since the height of a block is 1m, the elevation of

the bottom of bed-protection is designed at EL 299m that is lower by 1m than the elevation of current

river-bed EL 300m. In this case, as the difference of the elevation measured at around 50cm exists

between the apron and protection blocks, it is designed that the difference are attached on the surface

of blocks at their front edge so that they can be aligned to the current shape of the river-bed.

2-2-2-2-4 Examination of apron

The evaluation of apron is examined to an assumed section which is shown in the following table

preliminarily derived from the above-cited elevation to give an examination on the relevance of this

assumed section.

In this examination, the result of the hydrological evaluation on the design flood discharge

（1,710m3/s）around the location of the planned section in comparison with the assumed section is

also shown.

Downstream

of head works(No.0+14.5m)

Crest of the weir

(No.0)

Upstream of head works (No.0-26m)

Q: discharge (m3/s) 1,710 1,710 1,710

A: Area of flow (m2) 166.89 254.38 269.94

v : flow velocity (m/s) 10.2 6.7 6.3

h : water depth (m) 3.29 5.35 6.62

Z: water level (m) 303.79 306.85 307.31

Fr: Froude number 1.94 1.00 0.88

Table 2-8: Result of hydrological examination at the planned site

2-15

(1) Examination of the length of apron

The length of the apron is determined referring to the method of evaluation described in “Design

Standard of Head works, Japanese Government” and “Technical Standard of Kasen Sabou, Ministry of

Construction”. As to the length of apron, it is designed as head works of floating type because the

foundation of the head works is gravelly, permeable one.

a) Examination on Bleigh’s formula

Bleigh’s formula is referred to “Design Standard

of Head works, Japanese Government”

L＝ 0.6・C・√D1

where L : Length of rear apron（m） C: Bleigh’s coefficient 6（bounding stones, gravel/

sand ）

D1: Height from the surface of rear apron to the crest

of the weir 1.00（m）

L＝ 0.6×6×√1.00＝3.6m 4.0m

b) Examination on Rand’s formula

Rand’s formula is referred to” Technical Standard

of Kasen Sabou, Ministry of Construction”.

W / D = 4.3 ( hc / D ) 0.81

where W : Length of apron（m） D : Height difference 1.00（m）

hc : Critical water depth at the crest of the weir assuming the design discharge 1,710m3/s 5.35（m）

W = 4.3･D ( hc / D ) 0.81＝4.3×1.00× ( 5.35 / 1.00 ) 0.81＝16.7m 17.0m

Foundation Bleigh’s C Weighted Creep ratio C’

Silt or precipitated mud 18 8.5

Fine sand 15 7.0

Medium sand － 6.0

Coarse sand 12 5.0

Fine gravel － 4.0

Medium gravel － 3.5

Gravel & sand mixture 9 －

Coarse gravel containing boulder

－ 3.0

Bounding stones containing boulder and gravel

－ 2.5

Bounding stones, gravel and sand

4～6 －

Table 2-9: Bleigh’s C and Lane’s weighted creep ratio C’

Fig 2-6：Assumed section of the weir body

2-16

c) Determination of apron length

From the result obtained as above by means of

both formulas, the examination result is

summarized in the table shown in the right, thus

the length of the rear apron is determined as :

L=17.0m.

(2) Examination on piping

Examination on piping is made by means of the assumed section of weir body mentioned above. The

method of examination is derived from Bleigh’s and Rand’s formulas indicated in “Design Standard of

Head works, Japanese Government”. It is concluded from the following examinations that the

assumed section is judged safe against piping.

・Bligh’s method

S ≧ C・ΔH

where S: Length of path of percolation measured along the foundation face of the weir（m） Σ V＝2.50 + 2.50＝5.00m Σ H＝14.50m（length of weir body at upstream side） S = Σ v + Σ H = 5.00m + 14.50m = 19.50m C : Bleigh’s coefficient 6［above-cited］

Δ H : Maximum difference of water level between upstream and downstream sides 3.06（m）

6×3.06 = 18.36（m） ≦ S = 19.50（m） judged as safe

・Lane’s method

L ≧ C'’・ΔH

where : weighted length of percolation path（m） L =Σ V + 1/3･Σ H＝5.00m＋1/3×14.50m＝9.83m V : Length of percolation path to vertical direction（45° or steeper） 6.00（m）: the same as the examination by

Bleigh’s formula H : Length of percolation path to horizontal direction（45° or gentler）14.50（m）: the same as the examination by

Bleigh’s formula C' : Weighted creep ratio 3.0（bounding stones containing boulder and gravel: referred to above table）

ΔH : Maximum difference of water level between upstream and downstream 3.06（m）

3.0×3.06 = 9.18（m） ≦ L = 9.83m judged as safe

(3) Examination on the thickness of apron

The examination on the thickness of apron is made referring to “Design Standard of Head works,

Japanese Government” It is concluded from the following examinations that the safety of the assumed

section is secured.

t = 4/3 ×（ΔH – Hf）/（γ-1）

where : thickness at the point in consideration（m） ΔH : Maximum difference of water level between upstream and downstream sides 3.06（m） Hf = H / S × S' : Head loss of seepages up to the point in consideration（m） γ : Specific gravity of the material of weir body and apron 2.35 4/3 : Rate of safety

Method of examination

Length of apron Judgment

Bleigh’s formula 4.0m

Rand’s formula 17.0m ○ (adopted)

Table 2-10: Apron length by means of both formulas

2-17

S : Total designed length of path of percolation: 19.50（m）: the same as the examination by Bleigh’s formula

S' : Length of path of percolation to any point（m）

・Examination at the point A（downstream of the fixed weir）

3.06 HfA =

19.50×（2.50 + 3.50）= 0.94（m）

4 3.06－0.94 ＴA =

3 ×

2.35－1 ＝2.09（m）≦ 2.50（m） OK

2-2-2-2-5 Examination of bed pitching

(1) Examination on the length of bed protection

Bed protection is a facility to sustain the stability of river-bed against the supercritical flow which is

occurred by the hydraulic jump phenomenon in order to dissipate the water energy. Therefore, a length

of protected bed is hydraulically required enough to make hydraulic jump. However, since the target

river is a torrential stream with an average river-bed gradient of 1/60, river flow during floods

becomes almost jet flow, hydraulic jump required for energy dissipation does not hydraulically takes

place.

By this reason, the scale of the bed protection is designed at minimum requirement for the purpose of

preventing scouring at downstream apron or disturbance at river-bed surface.

In this design, the length of the bed protection is examined by means of Bligh’s formula in line with

“Design Standard of Head works, Japanese Government”.

L = Lb - La

Lb = 0.67・C・ （Ha・q）・f

where L : length of seed protection（m） Lb : Total length to protect including the length of the apron "La" and that of bed protection "L"（m） a : length of rear apron（m） Ha : Maximum difference of water level between upstream and downstream 3.06（m） q : Discharge per unit width derived from design flood discharge（Q = 1,710m3/s）（I m3/s/m） B : Width of waterway at the design section 45.3m = 39.8m + 5.5m q = Q / B = 1,710m3/s ÷ 45.3m = 37.7 m3/s/m f : Safety ratio in the case of fixed weir 1.0

C : Bligh’s coefficient by type of foundation ground 6

hence: Lb = 0.67×6× （3.06×37.7）×1.0 = 43.18 m（Required length including apron and bed

protection）

La = 17.00m （Total length of apron）

L = 43.18m – 17.00 = 26.17 m

From the result of above-mentioned examination, the necessary length for bed protection 26.17m

or longer is adopted as the extent of working bed protection.

2-18

(2) Examination of blocks for bed protection

Unit weight of a block is determined through the examination of the stability per piece of block in

conformity with the following formula described in “Design Standard of Head works, Japanese

Government”.

2g･W Ua＝(

3.19･A )1/2

where A : Area of collision of river flow（m2） W : weight of a piece of block（t） Ua : Allowable flow velocity （m/s）

Weights of a piece of block corresponding to various velocities are given in the following table. In this

regard, because the block is manufactured by cast-in-place concrete, conventional crop-shaped block

is employed for this type of structure.

Table 2-11: Weight of a piece of block and allowable flow velocity

Specification 3 ton 8 ton 8 ton × 2 connected

Size of block (m)

Weight of block 3.4 ton 8.2 ton 16.4 ton Area of block surface collided by flow

1.70 x 0.2 = 0.34 m2 2.80 x 0.2 = 0.56 m2 (2.80 +2.10) x 0.2+ = 0.98 m2

Maximum allowable velocity 7.8 m/s 9.5 m/s 10.2 m/s

Since the flow velocity likely to occur at the downstream of the head works during the design flood

discharge is estimated at about（1,710m3/s）10 m/s as a result of hydraulic calculation, blocks of a

specification with combined two pieces (8 ton/piece × 2) is adopted, because it can allow the

maximum flow velocity of 10.2m/s.

2-2-2-2-6 Examination of collecting channel

The design of the type of water intake below bar screen is based on “Design Standard of Head works,

Japanese Government”.

(1) Design of bar-screen

In “Design Standard of Head works, Japanese Government”, the interval of

bars used for the type of intake beneath the bar screen is generally given in

a range between 20mm and 30mm or so, however, it also points out that

choking often takes place over the screen. Therefore, taking account of

bar-intervals in case studies and of current state of river-bed sand and

2.80

Fig 2-7：Section of screen

2-19

pebble, the interval of 40mm is herewith adopted.

Also, regarding that a lot of bounding stones are observed in this river, the diameter of the bar is

designed at 100mm so that it can bear the hitting of bounding stones with the diameter of about 2m.

(Refer to the Appendix for the calculation of bar screen )

Assuming the above described conditions, the length of bar-screen, namely the width of collecting

channel is calculated. The length of screen bar is given as L0 in the below equation according to

“Design Standard of Head works, Japanese Government”. In this context, the width of water flow

surface at the main stream during dry season has been measured at about 25m in the site study (in

February), Taking this observation into consideration, the examination of the width of screen to be

installed is examined in this range of width. Also, in addition to the length of bar calculated below, the

extent of flow where water curtain along the surface of the bars is added to obtain the required length

of bars.

L = 2.8 Lo : Required length of bars

qo Lo =

μ･ψ･B･ （2ｇEo）where Lo : required length of bars necessary for collecting the whole amount of water requirement（m）

Qo : Discharge quantity（2.24m3/s） qo : Discharge per unit width（0.09m3/s/m = 2.24 m3/s ÷ 25m ） μ : Inflow coefficient（0.60） ψ : Degree of aperture（Σa / B, a : Width of bar-interval）ψ＝40 / 140＝0.286 B : Width of installing bar-screen（25 m） Eo : Energetic water head measured from the bottom of waterway at the upstream side（m） Eo = 1.5･hc＝1.5（q2 / g）1/3 hc : Marginal water depth（m）

g : Gravity acceleration（m/s2）

The following shows the result of this calculation. The height of the crest of the fixed weir is

determined as 0.90m＋0.20m＝1.10m, assuming the width of collecting channel at 0.9m, and

considering 0.2m as the space of installing bar-screen.

(2) Design of collecting channel

Considering that pebble and sand the sizes of which are smaller than 40mm are mixed in collected

water that flows inside the collecting channel, it is required to design it with a channel gradient that

does not allow the sedimentation of these solids inside it. As a range of gradient; 1/30 ~ 1/20 is given

in “Design Standard of Head works, Japanese Government”, larger gradient 1/20 is adopted here.

Since the depth of colleting channel should have the capacity of conveying the design intake

(2.24m3/s）, a calculation of the water level is performed based on the following conditions of the

B q Eo μ ψ Lo Ｌ＝2.8･Ｌo Remarks

(m) (m3/s/m) (m) (m) (m)

25.00 0.090 0.141 0.60 0.286 0.314 0.879 ⇒ 0.9m

Table 2-12: Calculation of bar-length

Fig 2-8: Required length of bar

2-20

Photo 2-1: State of the river-bed at planned site of head k

examination to determine the required depth.

L : Width of the collecting channel to the flow direction（0.90m） B : Width of the collecting channel to the direction of traversing the river（25.0m） n : Roughness coefficient of the collecting channel（0.016） I : Gradient of the collecting channel（1/20） Q : Discharge under examination（2.24 m3/s） ho : Water depth at the start of calculation（1.318m）※This value is equal to the sum of the water depth equivalent to the design discharge and 60% of the velocity head

The water depth of the downstream edge of the channel is calculated at 1.318 m from the above given

dimensions. Therefore, taking account of freeboard against the undulation of water surface and the

mixing sand and pebble, the depth of the collecting channel is designed at 1.318 m + 0.50 m = 1.818

m 1.80m. In this regard, water depth at the downstream edge of the channel is designed at 1.80m +

0.50 m = 2.30 m considering the thickness of the top cover of culvert (0.5m) for the purpose of

connecting the channel to the culvert at the downstream. The depth of the collecting channel at the

upstream side is designed at H = 2.30m - 1/20 × 25.00m = 1.05 m because the gradient of the channel

is I＝1/20.

The following shows the traversing section of collecting channel.

2-2-2-2-7 Surface protection work

(1) Necessity of constructing surface protection

work

Taklai river represents a torrential stream with

mountains of the altitude 2,000 ～ 3,000m as its

watershed. Huge rocks/ stones with their diameters

over 2m are scattered over the river-bed, large heap of

sand/ gravel deposits are also identified there (refer to

the photo).

In the case of installing structures under such conditions, it is suitable to judge the relevance of

Table 2-13: Result of the calculation tracing the water surface inside the channel

Fig 2-9: Section of collecting channel

Water depth

h(m)

D.S 0.00 0.000 2.240 1.318 1.187 3.537 0.335 1.888 0.182 0.000 1.500

U.S 25.00 1.250 0.172 0.310 0.279 1.519 0.183 0.617 0.019 0.004 1.579

No.Accumulatedistance (m)

Bed level (m) Q(m3/s)Wetted

perimeter(m)Hydraulicradius (m)

Area forflow (m2)

Velocity(m/s)

hv(m) hf(m) EL(m)

2-21

constructing them by considering correlation between such environmental conditions as density or size

of bounding stones or river-bed gradient and the relative strength of the planned structures. However,

concrete and numerical evaluation is difficult in the lack of streamlined references related to this

domain.

As a conventional clue for judgment, a tendency

as tabulated above table can be obtained from the

examined relation between the current width of the

river and the target flood discharge

（1,710m3/s）.This table shows example cases that

have statistically been studied and listed in “Design

Standard of Head works, Japanese Government”

and “Technical Standard of Kasen Sabou, Ministry

of Construction”. The conditions found in this

target site and the exemplified cases in Japan are not necessarily accorded, although it is evaluated that

assuming the flood discharge of 1,710m3/s the corresponding width of the stream should mostly range

120m～160m (in this assumption, high discharge and the flood are deemed as the same). Whereas, the

example of Taklai River gives too narrow width, namely about 60m.

Similarly, a calculation based on this table for the discharge per unit width gives 28.5m3/s/m in the

case of Taklai River, implying that the scale of the force of river-flow and energy during floods

accompanied by bounding stones and pebble are considered fairly large as compared with ordinary

streams listed up in the example cases.

In other words, in constructing concrete structures in the target river, it is readily imagined that

collided/ flood damages of the structures will be resulted in a few years unless protective or

reinforcing measures are applied, eventually leading to early loss of water intake function. In particular,

one of the reasons why medium and small scaled fluvial structures like weirs has not been constructed

in Bhutan.

Accordingly, in designing head works, it is planned to lay relevant protecting/ reinforcing materials

over the surface of the structure body where flood flow directly contacts. Work measures to be

proposed for this objective are to be judged with referring to the examples of construction work

actually implemented as protection measures shown in “Design Standard of Head works, Japanese

Government”.

General causes that bring wearing and deformation over the surface of apron are the actions of impacts,

abrasion, cavitations etc by the flowing down of sand and gravel. Particularly, Taklai River has a

character of accompanying bounding stones under the condition that huge flood discharge passes

narrow stream width, and this is why impact shock of bounding stones is greatly concerned as the

cause of deformation.

Even though a construction work existed that is semi-permanently durable against impact shock of

Designed high discharges (m3/s)

Width of river (m)

Discharge per unit width

(m3/s)

300 40~60 7.5~5.0

500 60~80 8.3~6.3

1,000 90~120 11.1~8.3

2,000 160~220 12.5~9.1

5,000 350~450 14.3~11.1

This site (Taklai River)

1,710 About 60 28.5

Table 2-14: Examples related to designed high discharges and stream idth

2-22

huge bounding stones under the above-cited conditions, it may be physically difficult or becoming too

large scale and economically consumptive. Therefore, it would be considered relevant to apply

measures that can allow to make a premise of regular management of repairs and maintenance. To

realize this measures, the work that can provide certain strength that is readily repairable, at the same

time that can repair with cheap materials is considered suitable. Accordingly, in selecting the method

of protection work for the apron, attention will be paid to the following criteria based on the basic

principles:

1. A premise is placed to be repaired and maintained regularly for apron.

2. In order to be repaired readily, the serious damage is prevented and the materials that can

readily be available in Bhutan are used.

3. Protection work for apron is selected in the process of the evaluation on the effect against

damages not only by abrasion but also by collided shock by bounding stones.

(2) Kind of protection work for apron

Various kinds of apron protection methods have been proposed from past example cases as shown in

“Design Standard of Head works, Japanese Government”. According to this standard, surface

protection methods are roughly classified into three categories, namely ①making the anti-abrasive

coating layer over the surface of concrete,②mixing anti-abrasive material in the cast concrete and ③

improving quality of concrete. In this evaluation, two more methods are added, namely “high strength

concrete containing rail method” and “high strength precast concrete method” as implemented

examples in Japanese head works.

Table 2-15: Kind of work methods for apron surface protection

Methods listed in “Design Standard of Head works, Japanese Government”

Method Method to form anti-abrasive film at the surface of concrete

Method to mix anti-abrasive material in concrete

Method to improve quality of concrete

Other works with actual examples of performances

Work

a) Stone protection work b) Steel protection work c) Epoxy resin-mortar d) Elastic sheet work e) Cast steel plate work f) Hyper-strength fiber

reinforced concrete

g) Iron powder concrete work

h) Steel grid work

i) Vacuum concrete work j) Granulisic concrete

work k) High strength concrete work

l) high strength concrete containing rail method

m) high strength precast concrete method

①Forming anti-abrasive film/coating at the surface of concrete.

a) Stone protection method

In this stone protection method in Japan, protection with cut stone, cobble stone, query stone etc

have hitherto been practiced providing excellent anti impact and anti-abrasive work. This was used

until around 1960, but recently rarely utilized due to technical degradation of masonry, difficulty of

procuring high quality stone materials, high construction costs and issue arising from detachment

from basement concrete. On the other hand, in development country where it is easy to obtain the

suitable stone, the masonry structure can be observed relatively.

2-23

Breakage of stone protection is not started with abrasion of paved stones but it is escalated by the

accelerated pulled/ fallen off of paved stone alignment, against which such device as to increase

length of stone edge is needed. In addition, it is necessary for preventing falling off of lined or

paved stones not to expose the part of mortar plastering between two adjacent stones or to make

stone surface as smooth as possible without leaving concave or convex part.

b) Steel board protection method

This method, consisting of anchoring steel boards to the basal concrete and fixing them with anchor

bolts and surrounding parts with welding, has effect of increasing impact or abrasion tolerance.

However, problems arise in such a way that steel boards separate from the anchored basal concrete

due to thermal stress, or steel boards are deformed to corrugated shape by impacts of collision with

boulder and bounding stones ad subsequently the convex part tends to be susceptible to abrasion,

thus much higher abrasion rate than the initial expectation has been reported. In addition, the work

is heavy because of the accompanied necessity of frequent welding, also requiring higher

installation cost equivalent to several times as much as that incurred for other protective measures.

c) Epoxy-resin mortar plastering work

Paste made of epoxy resin and silica sand (quartz sand containing high glassy ingredient) is utilized

in this work, and this mixture has anti-abrasive character. It has strength of around 10N./mm2～

80N /mm2, with an excellent resistance against abrasion, but inferior resistance against impact

shock because of its thin coating about 20mm. It also has problem of detachment from the basal

concrete mass by defoliation.

d) Elastic board work

This method, consisting of anchoring elastic organic boards made of poly-urethane derivatives to

the basal concrete mass and fixing them with anchor bolts etc It has high impact-absorbing effect

by the elastic boards, with excellent anti-impact and anti-abrasive natures. Nevertheless, it has a

weak point of its adhesion with the basal concrete. In recent years, coping with washing away loss,

such measures have been taken such as “gear-fitting shape” fixing in order to prevent corrosion of

fixing iron fitting or stripping of elastic boards. This work also incurs high cost several times as

much as that of other protective measures.

e) Cast steel plate work

This method, consisting of anchoring anti-abrasive cast steel boards made of poly-u attached to the

basal concrete mass and fixing them with anchor bolts, is excellent tolerance against impact shock

and abrasion. it has also similar problem to that of the above-mentioned elastic board method.

f) Hyper-strength fiber reinforced concrete work

Hyper-strength fiber reinforced concrete work utilizes buried forms in which cement milk is filled

by grouting. Buried forms are manufactured in factories. The resulted concrete has strength against

compression of about 150N/mm2, with excellent resistance against abrasion.

2-24

② Mixing anti-abrasive material in concrete

g) Iron powder concrete work

Soon after casting concrete, iron powder is spread over cast concrete surface as thick as 3 ~ 4 mm

so that iron can be unified with cast concrete mass. However, detachment is readily induced

because of iron has different expansion coefficient from that of concrete. This method does not give

so much excellent resistance against abrasion and is susceptible to impact damages.

h) Steel grid work

This method only replaces a part of fine aggregates of ordinary concrete with specially selected

iron particles, thus having almost the same characteristics as those of iron-powder concrete.

Therefore, it has not greater resistance against abrasion, and also it has weak resistance against

impact.

③ Improving quality of concrete

i) Vacuum concrete work

Immediately after casting concrete, moisture contained in concrete is absorbed out fro the surface

by vacuum treatment, thus making water cement ratio in concrete smaller and this leads to

improved quality of cast concrete itself (strength etc). Though the treatment can increase strength

against compression and resistance against abrasion by both 20 ^ 30%, it has weak resistance

against impact. Therefore, this method is suitable to rivers where less boulder / sand and gravel

bounding.

j) Granulisic concrete work

This work was utilized for the purpose of making crest of erosion and torrent control dams more

resistant against abrasion or of repairing weir body and apron. Water cement ratio in this work is

made extremely smaller without employing fine aggregates but only coarse aggregates and cement

paste are used for kneading so as to provide rich mix concrete with water cement ratio at around

30%. This mixture is excellent resistance against abrasion and impact, but as it is a kind of

hard-kneaded concrete with a slump of nearly 0cm, it has inferior workability in the case of using

large amount of concrete though it is suitable for small scaled work like repairing etc.

k) High strength concrete work

Rich mix concrete with lowered water cement ratio is employed in this work, showing both

excellent anti-abrasive and highly impact resistant nature. Nevertheless, in the case of construction

in rivers with abundant bounding stones, this material is often used combined with other members,

or other method is often selected. Construction work with this concrete is similar to that of ordinary

concrete, thorough curing after casting is essential because rich mix is used in this case, otherwise

risk of evolving cracks would increase. In the actual examples the strength of 30~50N/mm2 and

casting thickness of 30～50cm have been adopted. In particular, in the case of overseas works,

2-25

around35N/mm2 has been adopted partly because difficulty arises in securing high quality of the

materials or favorable work environment (referring to the performances in East Timor).

④ Other works with actual examples of performances

l) High strength concrete containing rail method

In addition to characteristics that high strength concrete is equipped, rail used for railway, a

member with high stiffness is placed in a screen shape over the surface for the purpose of

improving resistance against impact and high strength concrete is cast in between the placed rail.

m) High strength precast concrete work

This work consists of concrete sheets manufactured in factories that are carried to the site, then

filling cement milk by grouting after installing them on the surface of structure to be protected with

anchor bolts. The strength attained by this work is equivalent to that of high strength concrete,

namely 100n/mm2.

(3) Evaluation of protection work of the apron

Various case examples are available on the protecting work of apron surface as given above the

evaluation In here. The method of protection work for Apron is evaluated by following indicators, with

taking consideration current state of the site.

Table 2-16: Evaluation indicators based on the basic principles of the design

Evaluation indicator Contents of evaluation Resistance against abrasion Evaluation of resistance against abrasion caused by sand/ pebble and stone, referring to

the descriptions in existing references Resistance against impact Evaluation of resistance against impact shock caused by sand/ pebble and stone,

referring to the descriptions in existing references Workability Evaluating readiness/ difficulty of work in Japanese construction cases Material procurement Evaluating readiness/ difficulty of procurement in Bhutan Operation & maintenance Evaluating readiness/ difficulty in the case of repairing and maintaining facilities in

Bhutan

The following table shows the comparison on the above-listed evaluation indicators.

2-26

Tab

le 2

-17

: C

ompa

rison

tab

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f a

pro

n p

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ctin

g w

ork

Apr

on p

ro-

tect

ing

wor

k Ab

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on

resi

stan

ce

Impa

ct

resi

stan

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Wor

k-

abilit

y Pr

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ing

read

ines

s O

/ M

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adin

ess

Initi

al

cost

E

xam

ple

of p

erfo

rman

ce

Inte

grat

ed e

valu

atio

n

Ston

e pr

otec

tion

○

(2)

○

(2)

△

(1)

○

(2)

△

(1)

○

(2)

AIM

OT

O H

.W

UE

DA

H.W

H

AK

US

AN

H.W

10pt

Pro

cure

men

t of

mat

eria

l st

one

is c

onsi

dere

d po

ssib

le a

t th

e si

te t

houg

h pr

oces

sing

is

requ

ired

. W

ork

is p

erfo

rmed

by

skil

led

mas

onry

eve

n in

Ja

pan,

anx

iety

is

felt

for

the

wor

k te

chni

ques

in

Bhu

tan.

In

the

case

th

at s

ome

pile

d st

ones

fal

l ou

t, ac

cele

rate

d es

cala

tion

of

coll

apsi

ng

dam

age

is a

nxio

usly

con

cern

ed

Stee

l bo

ard

prot

ectio

n △

(1

) △

(1

) ×

(0

) △

(1

) ×

(0

) △

(1

) M

INO

WA

H.W

N

ISH

I IW

AS

AK

I H

.W

4pt

Wor

kabi

lity

is

low

bec

ause

of

a lo

t of

wel

ding

wor

k. I

n th

e ca

se t

hat

stee

l boa

rds

are

deta

ched

, rep

airi

ng a

t the

sit

e is

impo

ssib

le.

Epox

y-re

sin

mor

tar

plas

terin

g ○

(2

) ×

(0

) ○

(2

) ×

(0

) ×

(0

) ×

(0

)

KA

WA

I H

.W

TO

KA

TI

H.W

K

AW

AT

OU

H.W

4pt

Thi

s w

ork

has

infe

rior

res

ista

nce

agai

nst

impa

ct.

It i

s ne

cess

ary

to

proc

ure

mat

eria

ls i

n Ja

pan,

and

if

nece

ssit

y ar

ises

for

rep

airi

ng,

it i

s im

poss

ible

to r

epai

r at

the

site

.

Elas

tic b

oard

wor

k ○

(2

) ○

(2

) ○

(2

) ×

(0

) ×

(0

) ×

(0

) IN

UY

AM

A H

.W

SH

IN K

INO

MA

TA H

.W

6pt

It i

s re

quir

ed t

o pr

ocur

e m

ater

ials

in

Japa

n, a

nd i

f ne

cess

ity

aris

es f

or

repa

irin

g, it

is im

poss

ible

to r

epai

r at

the

site

.

Cas

t st

eel

boar

d w

ork

△

(1)

△

(1)

×

(0)

×

(0)

×

(0)

△

(1)

Exa

mpl

e of

per

form

ance

o

f th

is

case

is

no

t av

aila

ble

3pt

It i

s re

quir

ed t

o pr

ocur

e m

ater

ials

in

Japa

n, a

nd i

f ne

cess

ity

aris

es f

or

repa

irin

g, it

is im

poss

ible

to r

epai

r at

the

site

.

Hyp

er-s

treng

th f

iber

re

info

rced

con

cret

e ○

(2

) ○

(2

) ○

(2

) ×

(0

) ×

(0

) ×

(0

) S

HIK

AG

OU

H.W

K

AN

NA

GA

WA

H>

W

6pt

It i

s re

quir

ed t

o pr

ocur

e m

ater

ials

in

Japa

n, a

nd i

f ne

cess

ity

aris

es f

or

repa

irin

g, it

is im

poss

ible

to r

epai

r at

the

site

.

Iron

pow

der

conc

rete

wor

k △

(1

) △

(1

) △

(1

) △

(1

) △

(1

) △

(1

) IN

UY

AM

A H

.W

6pt

Ant

i-ab

rasi

ve o

r an

ti-i

mpa

ct s

hock

eff

ect

cann

ot b

e ex

pect

ed m

uch.

If

nece

ssit

y ar

ises

for

rep

airi

ng, i

t is

hard

to r

epai

r at

the

site

.

Stee

l grid

wor

k △

(1

) △

(1

) △

(1

) ×

(0

) △

(1

) △

(1

) S

AN

UK

I H

.W

5pt

Ant

i-ab

rasi

ve o

r an

ti-i

mpa

ct s

hock

eff

ect

cann

ot b

e ex

pect

ed m

uch.

If

nece

ssit

y ar

ises

for

rep

airi

ng, i

t is

hard

to r

epai

r at

the

site

.

Vacu

um

conc

rete

w

ork

○

(2)

×

(0)

×

(0)

○

(2)

×

(0)

×

(0)

INU

YA

MA

H.W

S

AN

UK

I H

.W

OK

AM

OT

O H

.W

4pt

Thi

s w

ork

has

infe

rior

res

ista

nce

agai

nst

impa

ct.

Als

o, i

f ne

cess

ity

aris

es f

or r

epai

ring

, it i

s im

poss

ible

to r

epai

r at

the

site

.

Gra

nulis

ic

conc

rete

w

ork

○

(2)

○

(2)

×

(0)

○

(2)

△

(1)

△

(1)

AZ

US

AG

AW

A H

.W

AIM

OT

O H

.W

8pt

Bec

ause

sl

ump

is

too

low

, ca

refu

l co

nstr

ucti

on

man

agem

ent

is

requ

ired

. M

ost

of p

ast

perf

orm

ance

s w

ere

lim

ited

to

part

ial

repa

irs.

W

hen

repa

irin

g is

nee

ded,

it’s

har

d to

rep

air

at th

e si

te.

Hig

h st

reng

th

conc

rete

wor

k ○

(2

) △

(1

) ○

(2

) ○

(2

) △

(1

) ○

(2

)

RO

KU

SE

KI

H.W

IS

HIB

E H

.W

AS

UW

A H

.W

10pt

Thi

s is

eas

ily

appl

ied

in o

vers

eas

wor

k be

caus

e m

ater

ials

do

not

requ

ire

any

spec

ific

ity.

Man

y of

rec

ent

expe

rien

ces

in J

apan

hav

e th

e st

reng

th o

f 50

N/m

m2 ,

but

in t

he o

vers

eas’

exa

mpl

es s

tren

gth

of a

bout

35

N/m

m2

beco

mes

upp

er l

imit

. In

the

cas

es w

here

spe

cifi

c re

sist

ance

ag

ains

t im

pact

is

requ

ired

, th

is m

ater

ial

is u

sed

toge

ther

wit

h ot

her

anti

-im

pact

sho

ck m

ater

ials

. Lar

ger

rang

e of

rep

air

are

need

ed i

n O

.M.

as c

ompa

red

wit

h th

e w

ork

cont

aini

ng r

ail.

Hig

h st

reng

th

conc

rete

co

ntai

ning

ra

il

met

hod

○

(2)

○

(2)

○

(2)

△

(1)

○

(2)

△

(1)

YO

KO

E H

.W

AIM

OT

O T

OK

OD

OM

E

SIR

OG

AN

E H

.W

10pt

Rai

l and

H-b

eam

mus

t be

proc

ured

in I

ndia

, and

they

are

not

so

spec

ial

mat

eria

l an

d so

pro

cura

ble

ther

e. T

his

wor

k is

esp

ecia

lly

exce

llen

t in

an

ti-i

mpa

ct

effe

ct.

Tho

ugh

abra

sive

de

form

atio

n ta

kes

plac

e ov

er

conc

rete

su

rfac

e in

be

twee

n ra

ils,

da

mag

e is

li

mit

ed

beca

use

it’s

su

rrou

nded

by

rail

. The

dam

ages

are

rep

aira

ble

wit

h co

ncre

te.

Hig

h st

reng

th

prec

ast c

on. w

ork

○

(2)

○

(2)

○

(2)

×

(0)

×

(0)

×

(0)

INA

OK

AW

A H

.W

6pt

It i

s ne

cess

ary

to p

rocu

re m

ater

ials

in

Japa

n, a

nd i

f ne

cess

ity

aris

es f

or

repa

irin

g, it

is im

poss

ible

to r

epai

r at

the

site

.

※ I

n th

e ev

alua

tion

in th

is ta

ble,

the

foll

owin

g po

ints

are

giv

en: ○：

2 pt

, △：

1 pt

and

×：

0 pt

2-27

From the result of comparison evaluation in the above table, feasible work with excellent anti-abrasive

and anti-impact effect and that materials are possible to procure in Bhutan as well as operation and

maintenance can be easy at the site is focused into two methods, namely, “①stone protection” and “②

high-strength concrete work containing rail. In this context, high strength concrete work also has the

same mark points as integrated evaluation, there remains a concern in the use of the this method alone

because it has lower on the resistance against impact in comparison with other two focused methods.

Therefore, it is planned to adopt this method at the sites where direct impact does not act or influence.

The following shows an image of “①stone protection” and”② Work with high strength concrete

containing rail. In this figure, although there are various kinds of stone protection work, both examples

are often observed in overseas construction work and those adopted for surface protection in Japan are

illustrated.

Stone protection work Stone protection often observed in overseas work Stone protection used for surface protection in Japan

・Outline Concrete mixed with stones of voluntary size (around 30cm in diameter or smaller) is cast. Another method is available that inserts stones from the rear side. This method is also utilized to save the volume of cment. In this case, boulder is mixed not only over the surface biut also in the internal space.

・Outline Stones of the size 300mm are paved over the apron. Stone used for this work are preliminarily processed for shape-up in preparation for paving in order. In most of Japanese cases purchased stone material is used.

Work with high strength concrete containing rail

・Outline H-beam for installing is paved over the surface of apron with a thickness of 0.5m and rail for railway is installed vertically to H-steel. Rail and H-steel are fixed be weldering or with fitting instrument.

The above-mentioned, two protection works, is examined to the apron where impact by bounding

stones is large. As to “①stone protection” and”② Work with high strength concrete containing rail”

adopted here will be evaluate in detail in the following:

Table 2-18: Stone pitching work, Work with high strength concrete containing rail（reference: Bolder concrete work）

0.5m

Flow

less concrete abrasion for thesmooth surface

Reduce the impact to the basestone for the smooth surface

set the processed stoneof 300 mm size so as topave in order

Side section of surface protection

2-28

① Stone protection

・As to resistance against abrasion, that against impact and workability of stone protection

Because stone itself used for stone protection is around 2 ~ 3 times as strong as general concrete, the

strength of stone is considered excellent as far as it is evaluated only in terms of quality of material.

However, the strength in the protective work for apron is given not only by the strength of individual

materials but as a unity of materials utilized in the work. Therefore, in order to make it effective for a

protective work, it is required to pay careful attention in the method of the work including; use of

appropriate quality of stone with enough strength, securing to fix stones with around the same size

(about 30cm in length) over the concrete matrix to be protected, securing smooth stone pavement

without part of outstanding convex or concave as possible because impact of bounding stones to such

undulated part may trigger to loose on the adhesion of paved stones to concrete matrix.

Photo shown in the right side illustrates an example of

weir in Japan to which stone protection protective work

has been applied. Stones are paved by skilled masonry

and the completed stone wall has been set in an excellent

order without any outstanding cavity.

In this work, it is important to set stones in the right

disposition and to keep quality control, and the work

used to be performed by skilled masonry staff in Japan.

However, recently this work hasn’t been applied due to

shortage of technicians. One of the reasons of requiring

skilled masonry originates is from the fact that this method has not publicly been authorized. It has

also been reported that this methods has not subjectively applied mainly because problem often arises

from falling out of some paved stones due to improper construction performances.

On the other hand, different from the above-described method, there is another way of the work in

which natural boulder pieces is used without any treatment or processing, only laying over the surface

of the apron. In this case, it is required to remove the any convex/ concave surface of stones as much

as possible, though some roughness is inevitably left, leading to inferior effect as a protective work.

As a conclusion, this work has higher difficulty ranking but if satisfactory work is performed and the

suitable stones are possible to obtain, a high effect can be expected as a protective work by low

materials cost. Notwithstanding, sufficient protective effect can hardly be expected under the situation

of failure of securing technical confidence/ credibility, thus escalated damage due to detachment of

paved stones is worried. Depending on the extent of damages, quick response for repairing may turn

out to be difficult.

・As to procurement of materials to be used in protective work and O/M of stone protection work

As a large quantity of bolder pieces is found in the site of Taklai River, procurement of the material is

Photo 2-2: An example of weir protected by stone pitching (Hakusan head works Ishikawa Prefeture

Flow

2-29

considered easily possible. Choosing pieces with their diameter of 40 ~ 50 cm among them, and

arrange them into the size of around 30cm by trimming them through processing, then paving them

through the work so that they can tightly adhere to the underneath concrete mass. In this case, number

of boulders necessary for covering the area of around 680m2 that requires protective work comes to

5,560, namely, assuming the size of boulder as 30cm x 30cm, interval width in between neighboring

boulder pieces as 5cm, 680m2 / (0.35m x 0.35m) = 5,551≒5,560.

In operation and maintenance, it is enough to repair the range of fallen out stones by the similar way,

but it is necessary to train and acquire the work techniques required for the construction period.

Further, if the state of paving boulder pieces at the time of construction is not favorable, the damaged

area would be greater.

② Work with high strength concrete containing rail

・As to resistance against abrasion, that against impact and workability of the work with high

strength concrete containing rail

Work with high strength concrete containing rail utilizes rail manufactured in factories under quality

control. The rail is fixed with bolts or by welding inside the weir body. Concrete used in this work can

also be provided under ordinary quality control, thus the work can be performed under relatively easily

secured quality of construction.

After the rail is fixed with bolts or welding, the fixed part can be covered inside the cast concrete, and

there remains no convex or concave part on the surface of the completed protective work, thus

loosening by the shock of impact hardly results.

On the other hand, since high strength concrete that is filled in the space between rails has inferior

resistance against impact to the fixed rail, some extent of damage by impact is inevitable. However,

considering the whole apron, the portion of concrete is surrounded by rails, thus the integrated strength

is exerted in this unified and continuous body, consequently leading to limited range of damages.

Besides, it is concerned that the part of rail is damaged

arising the necessity of changing/ renewing, but the

experiences in Japanese cases constructed in torrential

streams with greater impact of bounding stones shows that

there has not been such injury or necessity of change at

least for 30 years. It is judged that this fact verifies the

following: since the rail and the fixed part of rails are

protected by cast concrete, almost no worry remains of

washing loss of materials due to loosening.

The photo in the right shows a case of constructing this protection work in Japan. H-beam is installed

beneath the rail, and after fixed with the rail setting in the upper position, high strength concrete is cast

filling the whole space in unity.

Photo 2-3: A case of constructing the work of high strength concrete containing rail (Yokoe head works, Ishikawa Prefecture Japan

Flow

2-30

Thus, it is concluded that the work exerts enough strength as a protective work through the unification

with materials utilized, with high credibility of securing quality of construction.

In this context, the following 3 reasons imply

the fitness and effectiveness of the work of high

strength concrete containing rail to this river:

1. As regards discharge per unit width that

evaluate the energy during floods, the value of

Taklai River and that of Yokoe head works in

Japan that is the one of the cases where this work was applied roughly accords,

2. As regards environment where impact of the bounding stones exerted to the apron generates, Yokoe

head works have higher possibility of impact occurrence,

3. Under these conditions, no cracking or other serious injury has so far appeared on the apron at

Yokoe head works, thus the application of this method to the target river is considered relevant.

・As to procurement of materials to be used in protective work and O/M of the work with high

strength concrete containing rail

As to rail and H-beam, as they have not been manufactured in Bhutan, it is necessary to procure them

from India. In this regard, it is cost to procure and transport the rail and H-beam though, since both of

these materials do not require any particular specification, in other words they are generally dealt by

any steel producers, no problem arises to obtain them.

Quantity of each material to be disposed over an area of about 680m2 where surface protective work is

required comes to; rail: 17m x about 130 rail（equivalent to 40kg/m）, H-beam: about 39.5m x 5rod

（equivalent to H x B =250 x 125）.

Although a premise has been proposed that damaged parts over concrete filled in between rails should

pertinently be repaired and maintained, possibility of occurring some deformation on rail during

service period may remain, such damage or injury as requiring repair or renewal has not been given

for at least 30 years in the past experiences. Considering this fact, as to conceivable operation and

maintenance during service period, repairing damaged parts over concrete in between rails would be

needed. In the case of such repairing, fragile part around the damaged parts is removed and then fill

with new concrete, thus operation and maintenance at the site can readily be practiced.

(4) Apron protective work to be adopted

The selected two methods are evaluated in an integrated way based on the above-mentioned

comparative assessment, and the result of the evaluation is tabulated as follows, and it is finally

determined to adopt the work with high strength concrete containing rail.

Taklai River head works Yokoe head works

Design flood discharge 1,710m3/s 4,600m3/s

Length of weir About 60m 144m

Discharge per unit width 28.5m3/s/m 31.9m3/s/m

Height of weir 1.0m 7.4m

Table 2-19: Faciliy environment of Taklai River head works andYokoe H.W

2-31

Table 2-20: Table of comparison to determine the work to be adopted

Stone protection work High strength concrete containing rail

Since the strength of individual stone pieces is sufficient, excellent anti-impact and anti-abrasive effect can be expected, provided that adhesion between aligned stones and concrete mass beneath them is secured. However, unless construction work is properly carried out, function as a protective work that is exerted by unified mass with the apron can hardly be expected, emerging falling out of the paved stones that may be escalated to enlarged range of damages.

Quality of construction can readily be secured under this work, the strength is exerted as a protective work through the unification of the protected body and materilas utilized for protection with a high quality. Though damages to high strength concrete cast and filled in between rails are inevitable, rail and apron concrete can continuously be fixed and exert integrated strength, thus the damaged range is limited.

Resistance against impact and abrasion

○ ○ Since high level of construction techniques is required, actual performances with this method is few in Japan. Construction techniques should also be ensured and it is important in the case of applying this method in Bhutan, but construction quality is hardly secured because of lack of clear construction standard for this work.

Since rail that is produced in factories under quality control is used inside the weir where it is fastened with bolts or welded, and also concrete can be cated under quality control by contractor, therefore sustenance of construction quality control is relatively easy.

Readiness of construction quality control

△ ○ Materials can be obtained in and around of the site. At the initial construction stage, about 5,560 stones are required. ・Initial cost of constructing surface protective work （including materials and construction works） Target area：680m2 Stone material：5,560

3,900Nu/m2（wet masonry and processed works） 3,900Nu/m2×680m2＝2,652,000Nu

2.7 million Nu / set

Such steel materials as rail and H-beam are procured from India. but since they are not materials that need special order, supply of these is easily available。 However, cost is highly incurred as compared with stone protection. ・Initial cost of constructing surface protective work（including materials and nstallation & construction） Target area: 680m2 Rail: 17m x about 130（equivalent to 40kg/m）, H-steel: about 39.5m x 5（equivalent to H x B =250 x 125 ） 10,900,000 Nu（rail works including materials）

3,000,000 Nu（materials for rail fix and works ）

13.9 million Nu / set

Procurement of materials

○ △ Even damages take place, procurement of repairing materials is easy. However, it is necessary to master and learn the construction techniques at the construction stage from Japanese technician. Also, if the state of paving stones at the construction stage is not proper, damage occurring later would be escalated and the range of requiring rehabilitation becomes larger. ・Estimated O/M cost （Contents of repair: chipping concrete and repair of stone protection）

4.6000 Nu / m2

Necessity of repairing damages on high strength concrete may arise. Because rail itself has high stiffness and it is fixed with bolts or by welding, necessity of replacement wouldn’t arise during the service period. In this regard, normal strength concrete is used for repair, the strength after repair becomes weaker than original design.

・Estimated O/M cost （ Contents of repair: chipping concrete and rehabilitation）

600 Nu / m2

Operation & maintenance

△ ○

Though this method is really excellent from material procurement point of view, apprehension arises from failure of security on the credibility of construction techniques and quality. If construction quality is defect, effect of surface protection may become weaker, leading to larger range of repair and damage goes beyond the possibility of rehabilitation. Although cost of the work is inexpensive, ensuring the effect as a protective work would be inferior.

Procurement of the materials is possible in India and repair of high strength concrete filling in between rails would be necessary as O/M during the service period. Though initial construction cost is more expensive than the stone protection, both credibility on the strength of the protective work and readiness of O/M after the construction are superior thereto.

Integrated evaluation

△ ○

（adopted）

2-32

(5) Protection work in other parts

As the overflowing part of upstream

of the head works thrusts 1m at

maximum from current level of

river-bed, impact of bounding stones

is inevitable. Since this part has

bending structure, installation of rail

method examined above is difficult to

apply. Protective work with

steel-board can be considered to

partially protect with such processed

steel material. However, application

of steel-board protection work has

risk of washout loss induced, so it

arise necessary to consider again the

installation.

Re-installation of steel-board is done by welding new iron sheet in a way to close the washed out part,

but the tight contact with the under lying concrete is not so easily fixed, and usually another method of

fixing such as fixing by bolts. But it is obvious that such maintenance is almost impossible for local

facility keepers, thus protective work by means of concrete structure has to be adopted so that local

staff can manage it.

Considering all that is mentioned above, it is designed that boulder concrete is constructed at the

upstream of the weir body so that the excavated part is filled to the same level as that of overflow with

a gradient to the upstream side. Applying this structure, impact of bounding matters does not directly

contact toward overflowing part of the weir body. Then, the overflowing part of the weir body is

designed to construct with high strength concrete in order to reduce the abrasion. Also, downstream

slope of the overflowing part is designed to have the gradient of 1 : 0.2 that is adopted in order to

make less damages given by rolling bounding stones. Furthermore, the angle is trimming with a

circle-arch to reduce the impact of damages.

In this concern, the refilled part by bolder concrete does not unify with wire body itself. Therefore,

even though this part was more or less damaged it does not influence the function of the weir itself. In

addition, because this part is made of boulder concrete, it can readily and cheaply be repaired

whenever necessity arises to repair, also effect of preventing scouring at the excavated part can be

expected.

Fig 2-10: Range of applying apron protective work

2-33

2-2-2-3. Design of head race

Water diverted from the integrated head works

is conveyed to the 1st siphon of H.L.C. part

main through the head race running along the

river. Out of the total length around 1,050m of

the head race, 510m remains as earth canal and

the rest 540m is the canal of rectangular section.

Also, gabion baskets have been laid at a part of

the river side along the head race.

In this design, water intake by the integrated

head works and the connection of the head race

with the head works are reviewed, thereby

designing the structure secure the safety for any fatal influence of abrasion by abnormal velocity and

sedimentation sand occurring during intake and floods. The result of hydraulic calculation with design

flood discharge at the section of head race（1,710m3/s）is illustrated in the following figure, in which

red colored line indicates water level.

From this result, it is clear that the water level crosses over around existing pipe culvert along the

existing head race below the water level. It follows that necessity arises from this result to protect

canal from such as sand and bounding stones washed down by floods in the section of 360m from

head works. By this reason, it is designed as a culvert structure accompanying with bed protecting

work. Also, if any gate facility is installed along this section, it cause an obstacle against flood flow.

Therefore any gate facility is not installed in this section so as not to prevent flood flow. In this

connection, as to the downstream side of this 360m section, the head race canal is designed as open

canal because the flood water level runs below the existing head race.

Fig 2-11: Disposition of existing head race and existing gabion revetment

Planned site of head works Existing pipes culvert

Designed section of culvert Designed section of open canal

(about 360m)

Fig 2-12; Vertical section of the river

2-34

(1) Structure of the part of culvert

The structure of the culvert body is designed as concrete considering readiness of local operation and

maintenance along with the basic principles. Inner cross section of the culvert is designed in

consideration with the construction ease of the concrete work and practicability of O/M as the

following: assuming H × B = 1.0m × 1.5m, verified with Manning’s formula, to ensure a

cross-sectional area of flow: 2.24m3/s.

In this concern, as the section of culvert

submerges under the water surface during floods

and risk of the damages by torrential flow or

abrasion may arise, it is designed to bury the

culvert body as far as possible. As a clue of

determining the depth of laying the culvert, the

bottom depth of the existing head race can be

made as a target elevation is roughly adjusted. And

the bottom line of the designed head race will be

connected to the H.L.C.

In this context, because of not installing any gate

at the integrated head works, the gradient of the

culvert is designed so that sand and gravel passing

bar-screen with the maximum diameter of around

30 ~40 mm do not deposit inside it.

Taking account of all mentioned above, canal gradient of the culvert section is designed at 1/150. The

resulting flow velocity to evolve and tractive particle size at this gradient are showed in the above

table, and the target particle size in this facility（30 ~40 mm）is not deposited in it. As to the

relationship between the crest elevation at the culvert and the bottom elevation of the existing head

race, it is shown in “2-2-3 Outline design drawing No. 3-1”.

a) Protective work at the river side

Embankment at the river side has risk of being influenced by abrasion, impact of bounding stones and

scouring.

Though it is difficult to quantitatively assess the influence of abrasion and bounding stones, influence

by these factors is considered limited as compared with the environment where the integrated head

works are planned because the vicinity of this facility is situated at the inner side of meandering at

river. Taking this into consideration, cross-section of concrete is designed at the minimum thickness

required for the river structures: more than 0.35m (sourced by Japanese Standard), but for the section

where velocity of the river flow is rapid, it is determined at the minimum thickness of the member for

apron described in “Design Standard of Head works”: 0.60m in order to reduce injuries at the surface

Designed intake

quantity Half of this quantity

Examined discharge 2.24m3/s 1.12m3/s

Water depth 0.607 m 0.371 m

Width of canal 1.500 m 1.500 m

Cross-sectional flow area

0.910 m2 0.556 m2

Hydraulic radius 0.335 m 0.248 m

Roughness coefficient 0.016 0.016

Canal gradient 1/150 1/150

Evolving flow velocity 2.46 m/s 2.02 m/s

Tractive particle diameter

About300 mm About 200 mm

Target particle diameter

30 ~40 mm 30 ~40 mm

Assessment result OK OK

Table 2-21: Tractive particle size at each level of discharge

Moving particle size (m) : d = Vc 2 / 20 where Vc (m/s) : marginal flow velocity to move

2-35

of wall that receives impact of stream flow. Similarly, to prevent scouring, it is designed to install

embedded foundation of 1m thick beneath the wall at the river side and, furthermore, to install bed

protection block for the flow velocity. The evolving flow velocity of the culvert section is calculated as

shown in the table below derived from hydrological calculations for the design flood discharge. The

dimensions of this block are determined referring to the afore-mentioned “2-2-2-2-5 Examination of

bed protection”.

The bed protection work applied to the culvert section is concrete block. In this connection, the

ranging about 290~360m at the section of head race as shown in the table is located

at the shallow position compared

with the flood water level, and the

flow area around this section is

culculated about 10% of the total

flow section. Under these

conditions, the mean flow velocity

around this section is predicted at

about less than half (3m/s）of the

mean velocity （ 6m/s ） .Taking

account of the flow velocity to be applied to the gabion layer as bed protection work ranges about 5 ~

4m/s, gabion work is designed to apply to the section between about 290~360m.

b) Preventing measures against scouring at the side of rock mass

The mountain side of the culvert section consists of compacted sand~ gravelly river terrace that is not

considered fully stable because it has been formed by sedimentation. Adopting such slope protective

work as concrete lining is concerned to secure a long-term stabilization of slope surface, but actually

the canal is planned to construct with a culvert structure, so the water-flow at culvert can be

guaranteed even if some extent of collapse took place over the slope.

By this reason, necessity of slope protection does not need. In addition, the river terrace at the right

bank where head race runs is located inside of meandering part of the river, the extent of collapse over

the slope is considered limited in a sporadic occurrence. In this connection, excavation of the

mountain becomes necessary in the course of the construction work, it is designed to arrange the

excavation gradient at 1:1.0 that gives stability over the sand/ gravelly mountain. At the same time,

since the section of culvert is submerged under flood water, gabion layers are to be laid over the range

of ground excavation up to the level of the top of the culvert- head race for preventing scouring.

c) Standard section of the culvert section

From the result of above-cited examination, the standard cross section of the culvert is given as the

following figure:

Evolving flow velocity in the culvert section and foot protection block to be applied

Applying section Section up to about160m from head

works

Section between 160~290m

Section between 290~360m

Examined discharge 1,710 m3/s 1,710 m3/s 1,710 m3/s

Flood level WL 303.8 ~303.4m WL 303.4 ~300.9m

WL 300.9 ~299.1m

Culvert crest elevation EL 300.5 ~299.5 m EL 299.5 ~298.6 m

EL 298.6 ~298.2 m

Water depth 3.3 ~ 3.9m 3.9 ~ 2.3m 3.9 ~ 0.9m

Section flow velocity 8 ~7 m/s 7 m/s ~ 5 m/s 6 m/s (3m/s)

Block to be applied 8 ton Block (P.V:9.5m/s)

3 ton Block (P.V:7.8m/s)

Gabion baskets(P.V:5.0m/s)

Table 2-22: Hydraulic calibration values & examination of applicable bed protection block

2-36

Section Section about 160m from head works Section of the range 160~290m Section of the range 290~360m

Outlined lay-out

Bed protection 8 ton Block 3 ton Block Gabion layer

(2) Planned outlet of the culvert

When flood flow enters into the culvert section, it is discharged at the flow velocity of about 4.0m/s at

around the outlet of the culvert. A dissipater facility is planned to install in order to prevent flood

damages to the canal. The basic type of the dissipater to be adopted is water-cushion. However, since

the vicinity of the planned installation site of the dissipater has a narrow topography, it is impossible to

install large sized dissipater. It follows that the size of water cushion is to be made minimum size, but

also gabion layers are laid over the bed of the canal in order to expect the additional dissipating effect

brought by the high roughness of the gabion.

In this regard, since water flow is temporarily stagnated at water cushion, the sediment of the

transported sand/ gravel with larger particles, 2 ~ 30 mm in diameter is predicted. To cope with this

sedimentation, a sand drain gate is installed. At the same time, flood flow is dissipated in this section,

surplus water is planned to release at this point to the river.

a) Design of dissipating facility (absorbing canal)

Hydraulic condition at the outlet of the culvert section during design discharge is calculated by the

following formula given in “Design Standard of Canals, Japanese Government”:

where Qa：conveyable water volume (m3/s) L：Length of culvert (360 m) A：cross section of the culvert (1.50 m2) D：Hydraulic radius ( 0.30 m) fe：inflow head-loss coefficient 0.5 h：Difference of elevation between flood level and height of ceiling of culvert outlet (9.04m = HWL 306.85 – WL 297.81.m) fo：outlet head-loss coefficient 1.0 f：Friction loss coefficient f=2gn2/R(1/3) = 0.0075) n：Roughness coefficient 0.016

Qa = 1.50 m2×√{ (2×9.81×9.04m) / (0.5+1.0+0.0075×360m / 0.3m) } = 6.16 m3/s

Va = 6.16 m3/s ÷ 1.5 m2 = 4.11 m/s

The scale of the dissipation facility is calculated so as to satisfy the following formula given in

“Design Standard of Canals, Japanese Government”:

P > 3M

where P : static water pressure at the terminal edge of water cussion (γw × Bo × Hn2/2 ) kN

M : change in kinetic mass at the position that falling water shoot reaches the bottom of water cussion (γw×Q

DL

fff

hgAQ

e

a

0

2

hbhf

+ h

D Hn

hDh2

Table 2-23: Standard cross section of the culvert section

Fig 2-13 Image figure of dissipating

2-37

×Vm/g) kN γw : unit volumetric weight of water: 9.8 kN/m3 Q : discharge (6.16 m3/s) Hn : wager depth at terminal edge of water cussion ( hD + h2 + V22/2g) m Vm : flow velocity at the moment that falling water shoot reaches the bottom of water cussion Vm = √( 2g ×(He1 + hf +hD + hb) m/s

Under the given condition, in the examination by the above

formula, about 3m is required for height of drop（hf + hD）

while around 6m is needed for the width of canal （Bo）and even

as long as about 10m is necessary for its length in order to obtain

the dissipation effect (refer to case 1 in the right). Nevertheless,

topography observed in the vicinity of the planned outlet of the

culvert section where the dissipater is to be installed is

characterized with neighboring with slope of mountain in the

right side while in the left side the elevation difference between

this site and the river-bed is only about 3m (refer to the overall

design map). Hence, the above calculated scale would result in

almost entire excavation of the planned site, an anxiety arises

from this result that the installation of the calculated scale

dissipater on the contrary may disturb the stability of the ground

of the site.

Accordingly, another case is assumed in which the range of absorbing canal is limited within the area

of dropping water, designing a scale of the depth of 1.5m, the width of 3.0m and the length of 7.5m

deriving from the scale of the culvert and the topographic condition of the site, then P = 10.4 kN、M =

5.1 kN is obtained（refer to Case2 in the above table）. Under this assumption, though P ≒ 2M < 3M,

energy dissipating effect can be obtained against the annual-mean scale of flood, and as measures for

the occasion of occurring the scale of the design discharge. So it is designed to lay gabion layers inside

the downstream canal so as to structurally satisfy the dissipating effect with this combination of

dissipater and gabion.

The following figure shows the cross section of the dissipating facility.

Fig 2-14: Cross section of the dissipater

1.50

1.00 1.50

1.70

1.00

1.00

Case1 Case2

Q (m3/s) 6.16 6.16

V1 (m/s) 4.11 4.11

He (m) 1.86 1.86

Δh1 (m) 3.00 1.50

h2 (m) 0.71 0.71

Δh2 (m) 1.50 1.50

V2 (m/s) 2.90 2.90

Vm (m/s) 9.77 8.12

Hn (m) 2.64 2.64

L (m) 3.90 2.82

9.75 7.06

10.00 7.50

B (m) 6.00 3.00

P (kN) 20.85 10.43

M (kN) 6.14 5.10

3M (kN) 18.41 15.31

Lr=2.5L (m)

Table 2-24: Examination of the scale of dissipater

2-38

b) Structure of spillway for surplus water

The spillway for the surplus wateris designed to construct at the downstream of the dissipating facility,

for which an examination is made deeming the difference between inflow quantities into head race

during floods: 6.16m3/s and design inatake quantity: 2.24m3/s, namely 3.92m3/s as surplus water.

The structure of the spillway is designed in a way that cut-out part is worked at the flank wall from

which surplus water is evacuated into the original stream. For determining its size, water depths are

calculated at the above-cited two levels of discharges, deeming the difference of these two depths as

the depth of overflow on the spillway, for calculating the length required for releasing the target

surplus quantity: 3.92m3/s, namely the length of the spillway. In this process, the length of the spillway

is derived from Forchheimer’s formula.

ho + h2Q = 2/3 × μ × √2g L × (

2 ) 3/2

3Q

ho + h1L = 2× μ × √2g × (

2 ) 3/2

where Q : (surplus)discharge (3.92 m3/s) μ : overflow coefficient 0.644 g : gravitational acceleration 9.8m/s2 L : length of overflowing apron (m) γw : unit volumetric weight of water 9.8 kN/m3 h1 : overflow depth at upstream side : 0.468 m = 1.468 m (depth of upstream side) – 1.00m (height of flank wall) h0 : overflow depth at downstream side : 0m （making 0 at the lower edge of the spillway）

3 × 3.92 0.468 +0 L =

2× 0.644 × √19.62 × (2

) 3/2 = 18.21m

As a result, the length of the spillway is determined at 18.21m or longer, to be constructed in the

section shown below:

(4) Structure of the section of existing open channel

Out of the section of open channel, that of rectangular section 370m long has longitudinal slope of

about 1/140, lined with concrete of a thickness of around 10cm. Because evolving flow velocity inside

the channel exceeds allowable velocity of concrete lined canal of the lining thickness of less than

10cm, namely 1.5m/s calculated by Manning’s formula (based on the Design Standard of Canal Works,

Fig 2-15. Cross section of spillway

2-39

Japanese Government), it is designed to reinforce it with 20cm thick concrete without re-bar. In this

case of this thickness of concrete, allowable velocity comes to 3.0m/s. The following shows the result

of this hydraulic calculation of the existing canal.

(5) Plan of sedimentation basin

Since any gate facility is not planned to install for preventing floods in the vicinity of the head works

in this planned head race of the target facilities, sand/ gravel flowing from the head works flows down

in the head race. Though it is designed with a canal gradient that does not allow sand sedimentation in

the head race, it is required to eliminate flowing down sand /gravel before flowing into the H.L.C.

For this purpose, in order to evacuate sand/ gravel with the diameter of 0.3mm or larger that is harmful

to the irrigation as described in the "Design Standard of the Head Works, Japanese Government", a

sedimentation basin is to be installed around the upstream of No.1 siphon where land space for

constructing the planned facility can be procured.

The design of the sedimentation basin is based on the Design Standard of the Head Works, Japanese

Government.

a) Gradient of the sedimentation basin

The gradient of the bottom of the sedimentation basin is

planned referring to the Froude number for “sand drain

channel” described in “Hydrological Design of River

Structures, Japanese Government”, marking at around Fr = 2.5.

Taking the connection to the existing canal into consideration,

the Froude number is calculated under the gradient of I = 1/35

assuming uniform flow. It gives Fr = 2.3 as shown in the below

table, and this value is to be adopted.

Existing section After reinforcing it

Examined discharge 2.24m3/s 2.24m3/s

Water depth 0.25 m 0.27 m

Width of the canal 4.50 m 4.10 m

C.S.* area of flow 1.138 m2 1.104 m2

Wetted perimeter 5.006m 4.639 m

Hydraulic mean depth 0.227 m 0.238m

Roughness coefficient 0.016 0.016 m

Canal gradient 1/140 1/140

Flow velocity 1.97 m/s 2.03 m/s

Allowable flow velocity 1.5m/s 3.0m/s

Judgment NG OK

* C.S.: cross-sectional

Existing section Discharge of sand draining 2.24m3/s Water depth 0.080 m

Width of the canal 7.000 m C.S.* area of flow 0.871 m2 Wetted perimeter 7.249m Hydraulic mean depth 0.120 m Roughness coefficient 0.016 Canal gradient 1/35 Width of the canal 2.57 m/s Fr 2.3 * C.S.: cross-sectional

Fig 2-16: Image of repair of rectangular sectioned open channel in headrace

Table 2-25: Hydraulic calculation of the existing rectangular sectioned canal

Table 2-26: Calculation of gradient of sedimentation basin

2-40

b) Width of the sedimentation basin

The width of the sedimentation basin in the case of draining sand with jet flow by giving bottom

gradient to the basin is calculated with the following formula according to “Design Standard of Head

Works, Japanese Government”.

where B : width of sedimentation basin（m） h : water depth over the precipitated sand sediment 1.13 m ※ Assuming that the thickness of the sediment sand is about 40cm, or two times as much as the depth of incised

part of sand drain channel: 20cm and the water depth over this deposited sand is assumed at around 1.13m. In this connection, water depth at the downstream channel of the basin is 0.33m.

Q : designed quantity of flow per sand drain ditch 1.12 m3/s = 2.24 m3/s× 1/2 α : coefficient taking account of velocity fluctuation within the sedimentation basin 1.0

k : ＝τc / (ρ･i ) = U*c2 / i

U*c2 = 134.6 ･d 31/22 (0.118 < d < 0.303 cm) ･･･Iwagaki’s formula ρ : density of water flow 1.00 tf/m3 i : bottom gradient of sedimentation basin ( = 1 / 35) d : particle size as target of treatment in cm (targeting around 2mm by the result of site study)

k = 0.04878 = 134.6 × ( 2mm / 10 ) 31/22 / (1/35) × 10-4

Calculation with the formula

1.0 × 1.122 B =( 1.132 +

0.04878× 1.132 ) 1/2 – 1.13 = 3.50m / vent

As the sedimentation basin is designed at two continuous basins, the width of water flow in the basin

is designed at 3.50 × 2 = 7.00m.

c) Length of the sedimentation basin

Length of the sedimentation basin is determined by the following formula derived from sediment

precipitation theory described in “Design Standard of Head Works, Japanese Government”.

Q L =K ×

B×Vg where L : length of the sedimentation basin（m）

K : safety coefficient or 2.0 Q : designed quantity of flow per sand drain ditch 1.12（m3/s） B : width of sedimentation basin 3.50（m） Vg : precipitation velocity of finest particles to let precipitate 0.131m/s（obtaining by proportional division in the values given in the table below）

Table 2-27: Value of allowable marginal precipitation velocity in turbid water

Specific gravity of turbid water Particle size (mm) 0.1 0.2 0.3 0.5 1.0 2.2 3.0

1.100 υg(m/sec) 0.003 0.010 0.025 0.049 0.085 0.140 0.194

α・Q2 B =( h2 +

k・h2 ) 1/2 - h

2-41

1.12 L = 2.00 ×

3.50×0.131 = 4.9m → 5.0m

As a result of above calculation, the length of the sedimentation basin is designed at 5.00m.

2-2-2-4. Reinforcement of the existing gabion wall

The existing protection work on the banks of head race along the Taklai River consists of slope

protection by gabion. As this protection has height of over 5m and a steep piling-up gradient of 1:

0.2, this structure is concerned to easy collapse by outer force. In the occasion of flood disaster in

2010 gabion laid as wide as about 500m was washed away by flood water and also upstream part of

head race was collapsed, eventually leading the failure to Taklai Irrigation Area for longer than a half

year.

At present, damaged gabion wall has been rehabilitated to maintain the original configuration. taking

this into consideration, design is made into consideration of the following with a premise that gabion

is utilized in the plan as it is currently placed.

(1) Method of reinforcing the existing gabion wall

Since back side of the existing gabion wall is an independent state of stability, earth pressure of back

side earth does not exert to gabion. Hence, concerned outer forces possibly exerting to gabion is from

the river side include flood pressure etc. Judging from this state, as a strategy of design for protection,

pertinent and economical design will be resulted from the use of the existing gabion work as it is and

additional protection work in front of the existing gabion layers to increase resistance against flood

flow and impact by bounding stones. In the table below is shown the some works to make it tolerant

against outer force, but from the standpoints of reinforcing effect and ease of construction, covering by

concrete retaining wall is considered appropriate.

2-42

Table 2-28: Methods of reinforcing the existing gabion protection

Protective work by protection with huge sized stones

Protective work by concrete retaining wall Protective work by concrete blocks

Structure

Placing huge stons of the required size in front of the existing gabion. Material available at the site is utilized, but large amount of material is necessary for this work.

Covered by concrete retaining wall that has suitable weight and thickness at the front side of on the existing gabion layers.

Concrete blocks with required weight are piled at the front of the existing gabion layers.

Designed flow velocity 5m/s～6m/s ditto ditto

Required weight or size

Diameter: 2.5m～3.0m（5t~8t） (slope of stone pile 1:1.5)

Thickness of materials: thicker than 35cm (thickness is determined by stability calculation)

Heavier than 3t～4t

Reinforcing effect

Because huge stones have high strength, high reinforcing effect can be obtained provided that stone piling is properly worked.

Since this is a common work for river bank protection, reinforcing effect is securely expected. In addition, because it has considerable thickness of the materials, it also has resistance against impact of small bounding stones.

This is also an ordinary type of protection. It is often adopted in the case of expecting bed protection and effect of dissipating waves. This method is considered inferior to that shown in the left column because of longer resistant surface for the water flow.

Ease of construction work

While hoisting weight reaches about 5t~8t, necessary radius of hoisting work comes to around 10m. Therefore, such heavy machinery as crawler crane is required for this work. It is practically difficult to pile up different shaped stones, also the work accompanies with danger. Since huge stones satisfying the necessary specification is not abundantly found in the site, it may be required to transport them from other places. Not recommendable due to not only its inferiority from ease of work, but also the limited usage of huge sized crane to revetment work is arisen economic waste.

Since the work utilized cast-in-place concrete, it has an excellent ease of construction. Economic concern may arise, because the section of the work is lengthy.

Though this work is similar to the construction of concrete structures, it has a different process that blocks are cast in manufacturing yard then piled up with a crane. From design concept point of view, this method has a similarity to the concrete retaining wall mentioned in the left, and reinforcing effect is also similar thereto, but it has inferior ease of construction because of additional necessity of piling up.

Appraisal

Though the work requires a large sized crane, its transportation to the site is difficult, and its usage is limited, resulting in uneconomical method. Collection of enough materials of huge stones is also difficult.

（×）

This method has high ease of construction and also high protective effect. As to economic issue, the quantity of concrete will be economized by examining the size of protection.

（○）

Though similar evaluation is made to the concrete retaining wall mentioned in the left, this method is considered to have inferior ease of construction because of additional requirement of work for piling up.

（△）

(2) Range of applying protection measures to the existing gabion wall

The range of protecting concrete retaining wall is planned by hydrological calculation in which

river-bed shape is considered. The length of the range towards the downstream side of the river is

2-43

determined equal to the range of the existing gabion layers adjacent to the head race: 410m. As regards

the height of the reinforced concrete retaining wall is determined taking account of increment of water

level caused by the meandering flow of the river added to the water depth which is calculated for the

designed flood discharge.

From the result of hydrological calculation at the typical section of the existing gabion work, water

level is derived as WL295.0~292.0m. Adding 0.6 m which is the height increase of the water level the

meandered part to this elevation, the height of water level reach HWL 295.6~292.6m.

Table 2-29: Calculation of water level increase at meandered part of river stream

Formula for the calculation Result of calculation

B : 80m

V : 5m/s

rc : 360m

Δh0: 0.65 m

Δh0=B･V2/g/ rc Δh1=Δh0/2

where Δh1 ：increment of water level by meandering (m) B ：Mean width of water surface in the mending section, Obtained from plane figure (80m) V ：Mean flow velocity in the vicinity of meandering part Obtained from hydrological calculation (5.3 m/s) rc ：Meandering radius Obtained from plane figure (350 m) g ：9.81m/s2

In this calculation, the range of rc<10 is adopted in consideration. Δh1: 0.56m → 0.6m

As a result, the water depth around the site is calculated at 2.6m as obtained from the ground level of

the existing gabion wall which is EL293.0 ~ 290.0m, adding as free board to this in consideration of

the influence by surface wave etc, therefore the height of the concrete retaining wall is determined at

3m.

(3) Examination on bed protection for the wall

From the result of the following examination, the depth of scouring likely to evolve is estimated at

around 2m. Since flow velocity of the examined section is estimated at around 5m/s, gabion layer is

planned to install within the depth of 2m as embedded foundation work, and it is also planned to re-fill

at the excavated range with gabion during the construction of concrete retaining wall.

According to “Planning and Design of Revetment / Groin”, maximum depth of scouring is estimated

by the water depth for the occurrence of mean annual maximum discharge, in which the relationship in

some studied cases is illustrated in the figure below. Although this is not necessary of relation between

Japanese example cases and Taklai River, because these are a different stream flow environment, it is

merely used as a rough standard to estimate the necessary range of embedded foundation

Fig 2-17: Water level at design flood discharge and water depth around gabion wall

2-44

The flood discharge during rainy season with one year of return period of Taklai River 790m3/s is

deemed as mean annual maximum discharge to examine and estimate scouring around the existing

gabion wall.

Around the existing gabion wall, flow area for the above-cited discharge is estimated in the following:

flow area; 184.169m2 and the width of water surface; 98.1m, from these mean depth; Hn comes to

184.169 m2 / 98.1 m = 1.88m. Similarly, meandering radius of the stream around the site is estimated

at about 360m derived from the land survey map then r / B =3.7 is derived. Under this condition,

Hmax / Hn = 2.2 is obtained from the table, and the maximum scouring water depth is calculated at;

Hmax = 2.2 × 1.88 = 4.136m. Hence, the maximum souring depth is estimated at 4.136m – 1.88m =

2.256m →2m.

In this context, flow velocity of the site becomes around 5m/s, the maximum value of velocity is

concerned partly reaching greater depending on the river flow condition because the flow energy is

strengthened at meandering part. However, taking consideration as follows;

・existing gabion wall still remain partly for more than 5 years after their rehabilitation,

・the water flow impact does not directly exert, because the planned bed protection work is almost

laid under the ground,

・the economy of the work should be considered because the planned bed protection as wide range as

410m,

Therefore gabion work is judged suitably effective as embedded foundation and bed protection

within above section.

(4) Structure of the existing gabion revetment

As a result of the above discussion, the reinforcing method of

the existing gabion wall is illustrated as the figure in the right.

The size of concrete retaining wall has been identified

through the calculation of stability for the independent

structure.

In this work, weep holes (φ50mm) are installed over the

Fig.2-18：Relationship between Hm/Hn at meandering part and r/B

Where Hm: maximum scouring depth (m) Hn: water depth at mean annual maximum discharge :1.88 (m) r : radius of the meandering part 360 (m) B: width of water surface at mean annual maximum discharge :98.1(m)

Fig 2-19: Cross section around gabion revetment 2-45

retaining wall to drain the rain water.

・Calculation Condition

The calculation section show in right figure

Concrete：23kN/m3、Behind water depth：2m、Internal friction of soil：φ35°、Wet unit weight：

19kN/m3（Submerged unit weight：20kN/m3）

・Result of calculation

For the overturning -0.258m≦ 0.417m (capacity.)：OK

For the sliding 1.50≦1.5 (capacity.)：OK

2-2-2-5. Protection dike at the downstream of Taklai River

At the point of the downstream of the river, about 2 km from the planned site of the integrated head

works, a natural diversion of flow line was formed at the right bank side during a flood that gave

damage of sweeping away to a part of farmland at downstream. To prevent the repeated damages, the

Bhutan side provided protection works by gabion

around beginning of inflow part, but all the work was

washed away by the flood occurred in 2010, thus this

section is currently left without any protection works.

To cope with such damage, a dike is planned to

construct for protection of farmland. In this plan, the

maximum height of dike is same level as the river

terrace at the existing upstream and downstream.

Fig 2-21: Location of the planned embankment

Fig 2-20 : Section for calculation

2-46

(1) Examination of the height of dike

According to the result of a hydraulic calculation, the flood water level during the designed flood

discharge （1,710m3/s）is almost the same as the calculated height of the planned dike, and any free

board to generally be considered cannot be considered due to the topographic limitation. However, the

designed dike can manage to prevent the invasion of the designed flood discharge into farmland. Even

if overflow of flood took place over the crest of the planned dike, the extent of overflow is considered

limited to a few dozen m3/s, it is judged that decisive influence to farmland rarely happens, thus the

construction of the dike is considered high effect.

The height of the crest of the dike is designed at the same as existing river terrace, namely 3.0m.

(2) Examination of width of the dike

The width of the dike is designed so as to fill with the required width for the designed flood discharge

（1,710m3/s）. Based on the Japanese standard, it is designed at 4m or wider.

(3) Structure of the dike

As the result of the above examination, the structure of the dike is illustrated below. The structure at

river side is made similar to the reinforcement by the existing gabion layers at upstream along the head

race, and the rear side is protected with gabion layers in order to prevent erosion by overflowing flood

water. In this occasion, in constructing the dike, firstly the trapezoidal section with the width of the

crest 4m, slope gradient 1:1.5 is worked, and later the section is trimmed to correspond with the

planned section for installing structure.

Fig 2-22: ：Flood water level at around the section of planned Dike

Fig 2-23：Typical section of Protection Dike

2-47

2-2-2-6. Existing main canal and related facilities

(1) Rehabilitation for the flow capacity of the Existing main canal and related facilities

The existing main canal and related facilities can almost flow the design intake discharge: 2.24m3/s

without any change in its section, however, there is a section in short of free board of the canal around

the outlet of the first siphon. It is therefore designed that this section is raised up the wall. In addition,

by the reason that not only free board of link canal is insufficient, but also flow velocity exceeds the

allowable flow velocity: 1.5m/s (based on the “Design Standard of Canal Work, Japanese

Government”), it is necessary to reinforce the canal bottom.

The discharge of the L.L.C. is 0.92m3/s which is less than half that of H.L.C. However, L.L.C has

almost the same section area as H.L.C. Therefore it is specified that L.L.C has sufficient capacity of

conveyance by the examination of H.L.C. on its flow capacity only.

Table 2-30: Evaluation and treatment of canal flow capacity Name of canal Shape of canal section Evaluation Method of treatment to improve flow Downstream side of first siphon at H.L.C.

Rectangle section (wet masonry)

Free board is not sufficient Actual Hfb =0.12 m < 0.15m = Fbr

The existing wall needs to rise up. 10cm more or less is added to existing wall in free board.

H.L.C Trapezoidal section(lined with wet masonry)ﾞ

Possible to use the existing section as it is Treatment is not necessary

Link canal Trapezoidal section(wet masonry)

Free board is not sufficient Actual Hfb =-0.09 m < 0.14m = Fbr

The bottom gradient of the link canal changes at every vertical drop. Therefore, the required height of wall is examined for each section divided by vertical drop. Also, as to canal gradient, it is individually examined by section. Here, only the notice is made on the necessity of raising up wall for the canal, as well of the reinforcement of the canal bottom for the section where flow velocity exceeds 1.5m/s.

The methods of reinforcing or of rehabilitating each of main canals are shown in “Outline Design Drawing

No.13”.

(2) Additional repair and rehabilitation of related facilities and canal section

As regards related structures, breakage and leakage of wall of wet masonry canals, stones dropped down

inside canals, operational disorder / degradation of water-stop of gates, exposure and cracking of siphon

tubes are issues to be coped with. For the broken parts it is planned to repair and replace. However some

related facilities is inevitable to receive the damage by strong force such as dropped stone or abrasion.

Therefore, as the basic policy for the rehabilitation and improvement for these structures, the concrete

works is adopted. Because the possibility of the continuous maintenance and suitable durability is required

for these structures

Also, at confluence between L.L.C and Link canal, gabion layer for dissipation is planned to install and be

closed by concrete retaining wall. In addition, a gate is designed to install to control inflow water from the

river.

Individual methods of repair and rehabilitation are shown in detail in “Outline Design Figure No.13 and

No.15”. The following pictures show the state of damages on the main canal and related structures.

2-48

Table 2-31: Evaluation with visual observation on canals and related structures

Name of canal Item (parts, place) Quantity Photo for reference Countermeasures

The part requiring rehabilitation at the damaged wall of the canal

L=115m

Wet masonry is rehabilitated for the recovery t.

The section requiring prevention of dropping stones from the mountain lying behind canal

L=200m

Concrete cover with 20cm thick is installed at the upper part of the canal

The road bridge constructed over the canal is required repair

2 sites

It is renewed into a concrete bridge of the dimension: B×L = 4.0m ×3.9m

The part requiring repair for the leakage from the bottom of the canal

2 sites

It is repaired by plastering mortar inside the canal, also lining concrete outside of the canal.

Damaged gates 8 gates

Gates are renewed.

The site where newly constructed check gate is required.

1site

A gate is installed.

The site where new construction of diversion gate is required.

1 site

The gate is exchanged.

The part requiring protection for the exposed siphon pipe L=45m

The exposed part of the siphon is covered by concrete.

High Level Canal

The part requiring repair for the broken siphon pipe 1site

Cracking is repaired with concrete lining.

Damage of masonry wall

Fallen stone

Mountain side

Exposed re-bar

Leaking water from canal

loss of spindle

Loss of spindle

Exposed siphon

2-49

The part requiring to install the screen for preventing dropping into the inlet and outlet of the siphon

4 sites

Screens are installed on the inlet and outlet of the siphon.

The part requiring repair for breakage at flank wall of the canal

L=20m

It is rehabilitated partly

The site where replacement of the gate is required. 2 sites

The gate is replaced. Low Level Canal

Confluence between LLC and link canal which need the counter measure for inflow of flood

1 site

A gate is installed to prevent invasion of flood flow.

The section where repair and rehabilitation of canals are necessary（ around the end point of the link canal）

L=40m

The existing canals are repaired.

Link Canal

The section where raising up wall is necessary

The whole section (L=980m)

---

The height of raising up by 20cm~30cm on average is worked and the bottom is thickened against the rapid flow velocity

Loss of the gate guide

End of link canal Inlet of siphon

In-flow of flood water

Section of earth canal Section of wet masonry

2-50

2-2-3 Outline design drawing

Drawing List

DRW No. Drawing Name Pcs

No.1 General Map of the Taklai Irrigation System 1

No.2 General Plan of Taklai River 2

No.3 Longitudinal Profile of Taklai River 2

No.4 General Plan of Head Works 1

No.5 Longitudinal Section of Head Works 3

No.6 Cross Section of Outlet of Box Culvert 2

No.7 General Plan and New Open Canal 4

No.8 New Open Canal 2 and Sedimentation Basin 3

No.9 Longitudinal Profile of Candidate Site for Protection Dike 1

No.10 Longitudinal Profile of Link Canal 2

No.11 Cross Section of Link Canal 4

No.12 Longitudinal Profile of High Level Canal 7

No.13 Rehabilitation Plan of High Level Canal 3

No.14 Longitudinal Profile of Low Level Canal 4

No.15 Improvement Plan of Existing Confluence 1

Total 40

2-51

00.5

12

Kilo

met

ers

Kal

i Riv

er

Mao River

Taklai

Rive

r

00

Ta

kla

i Irr

iga

tion

Sys

tem

in S

arp

ang

Dis

tric

t T

he

Pro

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for

imp

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me

nt o

f

Ge

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l Ma

p o

f th

e T

akl

ai I

rrig

atio

n S

ysyt

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Ｎ

Flow

Flow

Hea

d w

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nal

High

leve

l can

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2nd

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on

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C.G

3

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C.G

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C.G

8

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on to

Hill

C.G

9

C.G

11

C.G

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C.G

13

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Low

leve

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Earth

can

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Low

leve

l can

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Link

can

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Exi

stin

g R

oad

s

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L= 0

.98

km

L= 6

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m

L= 1

.04

km

L= 2

. 9km

C.G

1C

.G2

C.G

7

C.G

3C

.G4

C.G

5C

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C.G

10

L= 2

.2km

Prot

ectio

n D

ike

Gen

eral

Map

of

the

Tak

lai I

rrig

atio

n S

ysyt

em

No.1

2-52

BH 1

BH 2

BH 3

BH 4

TBM

1

305

310

310

315

300

310315

300

305

305

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2

Ｎ

RL'

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SC.8

SC.3

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SC.3

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SC.8

SC.9

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SC.6

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Gen

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27,000

We t m as on ry

G a bions

W e t ma so n ry

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R=28.85 m

23°3

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68,4

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n of

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lai R

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g G

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55,5

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11,8

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11,96

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in P

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1.0

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No.2-2

2-54

300.75

300.90

300.53

300.70300.47300.11300.20300.09300.01299.94299.85299.84299.87300.01

299.07299.24

299.02

298.84

298.06

297.79

297.88

298.09

297.60

297.07

297.27297.16

297.01

296.99

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296.22

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300

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75m

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klai

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in S

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150

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prov

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nal P

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Long

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nal P

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(1/2

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ter o

f Hea

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orks

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SC.4

SC.5

SC.6

SC.7

SC.8

Pipe

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ting

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m X

2

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1,03

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535.

5mEx

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SC.10

299.76

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-26.40

2.879.60

18.1318.7321.8223.8926.0727.9129.7331.6336.03

74.0079.20

89.26

94.05

113.99

121.47

137.05

154.44

161.89

178.49

196.67203.61

220.30

243.87

259.29265.38270.85275.91281.64

319.45

419.10

63.60

371.10

6.44

10.84

9.12

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00

1:150

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Bed

leve

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Exis

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er B

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249.83

291.58 482.79

300.47 91.68

298.41

298.13

297.90

298.31299.49

299.12

300.24

298.37

298.31

2.876.73

8.530.6

3.092.072.131.891.821.904.40

10.405.20

10.06

27.57

287.92

385.75

453.85

372.66374.11

375.62

406.90

2.37

19.93

7.49

15.58

8.39

16.45

16.60

18.186.94

16.69

23.57

15.426.095.475.065.73

2.42

6.28

31.58

12.20

28.94

10.13

34.75

53.211.44

1.51

21.15

EL 3

01.5

EL 3

03.53,

500

SC.11539.57 56.78+56.78

14,9

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00 10,0

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11,8

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2°0

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(303.50)301.50

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300.00300.00

299.00

299.00

EL 2

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EL 2

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EL

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11

EL 2

96.8

1

EL 2

98.3

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296

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299.20

298.97

298.91

298.74

298.67

298.60

298.47

298.14

297.27

296.81

296.81

296.81

296.81

296.81

299.10

23°3

0'0"

R=28

.85m

TL=6

.00m

SL=0

.62m

146,

200

New

Ope

n C

anal

1

EL 2

99.0

Hig

h w

ater

leve

l (1,

710m

3/s)

No.3-1

2-55

295

300

305

290

SC.12

SC.13

SC.14

SC.15

SC.16

581.79

679.41

777.79

909.60

953.42

SC.11482.79

Hor

izon

tal S

cale

1:1

500

Verti

cal S

cale

1:1

500

75m

03-2Ta

klai

Irrig

atio

n Sy

stem

in S

arpa

ng D

istric

t

H=1

:500

V=1:

150

The

Proj

ect f

or im

prov

emen

t of

Long

itudi

nal P

rofil

e of

Tak

lai R

iver (

2/2)

1:15

00

1:150

285

291.58

285.95

1st s

ipho

ne -

Inle

t(φ

800m

m)

Exis

ting

Hea

drac

e C

anal

L=

1,03

9.5m

Exis

ting

Con

cret

e C

anal

L=

535.

5mL=

131.

97m

Exis

ting

Earth

Can

al

Bed

leve

l of

Exis

ting

Hea

drac

e C

anal

Riv

er B

ed le

vel

28.94

99.00

97.61

98.39

131.81

43.82

1.202.371.41

1039.501040.69

1044.481043.06

86.08

SCAL

E H

=1:1

500,

V=1:

150

Long

itudi

nal P

rofil

e of

Tak

lai R

iver

(2/2

)

Assu

med

bed

leve

l

20,7

0011

,960

55,5

0025

,700

11,8

00

294.13

292.87

292.87

292.55

88,1

60N

ew O

pen

Can

al 2

287.00

146,

200

New

Ope

n C

anal

1SC.11539.57 56.78

+56.78296.81

EL 2

96.8

1

370,

030

Ris

ed u

p by

Con

cret

e on

Exis

ting

Hea

drac

e C

anal

37,5

00Se

dim

enta

tion

Basin

Hig

h w

ater

leve

l (1,

710m

3/s)

No.3-2

2-56

00-0Ta

klai

Irrig

atio

n Sy

stem

in S

arpa

ng D

istri

ct

H=1

:250

Gen

eral

Pla

n of

Hea

d W

orks

Gen

eral

Pla

n of

Hea

d W

orks BH

1

BH 2

BH 3

BH

4

TBM

1

TBM

2

EL 3

01.5

EL 301.3

EL

301.

5

EL 300.55

EL 300.45

EL 300.32

EL 300.26

EL 3

03.5

EL 301.5

EL 3

00.5

Exis

ting

rock

Exi

stin

g ro

ck

(Wing)

1,500

3,350

600350

25,0001,000

3,90

05,

300

9,20

0

6,50

0

14,9

00

350

250

4,00

013

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12,900

38,900 9,450

10,5

00

200

27,6

00

3,50

0

8,200 1,250

2,500 1,900

(Bar screen)

23,5

00

2,30

01,

000

3,34

016

0

1,800900

650

EL

301.

5

Flow

1:2.

0

1/20

1,00

020

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01,

200

EL

299.

0(be

d le

vel E

L 29

8.0)

8t B

lock

by

Bol

der C

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3,00

0

1,90

0 1001,00

01/15

0

20,0

00

1/15

0

1,30

0

9°38'15"

100

45,000

Riv

er G

augi

n S

tatio

nw

ith L

aser

Typ

e

C

D

C

D

EE

FF

GG

BBA

A

45°0'0"

1:1

Protection Work on Apron

Protection Work on Apron

3,30

0

200

5,500

43,150

1:5.

58

Box

cul

vert

Box

culv

ert

B x

H =

1.5

m x

1.0

m

400

5,310

Bar

scr

een

De

tail

40

S=

1:5

0

100

1,30

0

10040

8,70

0

460

4,00

0

Stee

l Bar

φ10

0

2,690

5,200

200

900

200

90039,800

3 5 30

2,45061

013

,000

4 ,0 9 0

3,100

1,70

0

2,400

1,700

950

5,910

12,6

50

4,400

8,590

5 ,5 90

3,15

0

3,95

07,

360

Gab

ion

300

120

300

128250122500

S=1/

10Se

c. A

-A

Fix

bolt

De

tail

of

Pro

tect

ion

Wo

rk o

n A

pro

n

Top

View S=

1/30

3000

＠30

00

S=1/

30Si

de V

iew

600

＠30

00

Ａ Ａ

50040kg/m Rail ＠300

H 2

50xB

125x

9.7x

6.9

H 2

50xB

125x

9.7x

6.9

Fix

bolt

40kg

/m R

ail

S=1/

10

Exp.

j t=

20m

mW

ater

sto

p B

=300

mm

Spac

er

Anch

or D

22

Det

ail

Spac

er

H 2

50xB

125x

9.7x

6.9

Flow

Anch

or D

22Fl

ow

40kg

/m R

ail

H 2

50xB

125x

9.7x

6.9

Hig

h st

reng

then

con

cret

e

@30

0

Bolder Concrete

Bolder Concrete

No.4

2-57

00-0Ta

klai

Irrig

atio

n Sy

stem

in S

arpa

ng D

istri

ct

H=1

:100

The

Proj

ect f

or im

prov

emen

t of

Long

itudi

nal S

ectio

n of

hea

d W

orks

Long

itudi

nal S

ectio

n of

hea

d W

orks

Sec

tion

A-A

S=

1:10

0

10,5

001,

000

200

900

1,24

0

3,34

010

,660

1,000

1,00

012

,000

1,00

04,

550

14,5

006,

000

27,0

00(B

ed P

rote

ctio

n)

1:0.2

EL

299.

0

EL

301.

5

160

Bar

scr

een

1,000

EL 3

00.0

1,000

1,0001,500

Bol

der C

oncr

ete

Hig

h st

reng

then

con

cret

e

3,500 500

4,000

500

Tie

bar D

19

pipe

φ30

pipe

φ30

250

Bold

er C

oncr

ete

Hig

h st

reng

then

con

cret

e

3,00

0

1,00

02,

000

Bold

er

Con

cret

e

Oil

pain

t50

0

EL

300.

5

2,100

850

EL 3

01.3

6,50

0

8t B

lock

by

Bol

der C

oncr

ete

250

950

500

2,500

1,100

600500

1,500

3,000

EL

300.

55E

L 30

0.45

Box

culv

ert

B x

H =

1.5

m x

1.0

m

3,90

35,

300

14,9

00B

ox C

ulve

rtB

ox C

ulve

rt

1:5.

58

Flow

1:0.2

500

1,30

01,

040

1,00

0

1,500

1,900

1,400

DL=

295.

0

10,5

001,

000

200

900

1,24

0

3,34

0

1,000

1,00

012

,000

1,00

04,

550

14,5

006,

000

2,000

1:0.2

EL 3

01.5

EL

299.

0

EL 3

03.5

EL 3

01.5

160

Bar s

cree

n

1,000

EL

300.

0

1,0001,500

Bol

der C

oncr

ete

Hig

h st

reng

then

con

cret

e

3,500 500

4,000

500

Tie

bar D

19

pipe

φ30

pipe

φ30

250

Bol

der C

oncr

ete

Hig

h st

reng

then

con

cret

e

3,00

0

1,00

02,

000

Bol

der

Con

cret

e

Oil

pain

t50

0

EL

300.

5

2,100

850

EL 3

01.3

10,6

606,

500

8t B

lock

by

Bol

der C

oncr

ete

250

950

500

2,500

1,100

600500

1,5002,500

1,30

0

1 :2 .

0

1,04

0

1:0.2

1,5001,500

3,000

1,000500

1,400

1,900

Flow

100

Sec

tion

B-B

S=

1:1

00

DL=

295.

0

27,0

00(B

ed P

rote

ctio

n)

1,100

300550250

Tie

bar D

19D

19 L

=1,0

00 @

1,00

0

1,00

0

Hig

h st

reng

then

con

cret

e

Bol

der C

oncr

ete

Tie

ba

r D

etai

lS

=1

:50

@10

00

EL 3

00.0

1,900

2,700

2,500

820

1/20

@10

00

@10

00

1/20

@10

00

3,50

0

2,000

500

200

800

400

1,800

1,000

510

Wat

er s

top

B=3

00

R=3

00R

=300

R=3

00

100

100

100

100

Wat

er s

top

B=30

0mm

R=3

00

1:1.0

1 :1 .0

1:0.5

1:0.5

pipe

φ30

@10

00

pipe

φ30

@10

00

No.5-1

2-58

00-0Ta

klai

Irrig

atio

n Sy

stem

in S

arpa

ng D

istri

ct

H=1

:200

The

Proj

ect f

or im

prov

emen

t of

Cro

ss S

ectio

n of

Wei

r

HW

L 30

6.85

m (Q

=1,7

10m

3/s)

25,0

0012

,900

1,00

0

38,9

00

2,000

1,000 2,500

5003,500

Bar

scr

een

5,500

EL 3

00.5

EL

301.

5

3,35

0

3,500

1,2001,800500

5,350

1,25

0

9,45

0

600

350

1,50

0

39,8

00

EL

300.

5G

abio

n

EL

300.

55

1,000 1,000

1,85

0

100

350350

350

5,50

0

250

4,65

050

0

700

350 500

2,45

0

1,700

39,8

0060

0

Sec

tion

C-C

S=

1:20

0

Se

ctio

n D

-DS

=1

:200

EL

299.

20

EL

303.

5

4,70

03,

000

EL

301.

5

Box

cul

vert

B x

H =

1.5

m x

1.0

m

Exis

ting

rock

2,00

01:1.0

1 :1.0

43,1

501,

700

500

700

350

1:1 .0

DL=

295.

0

EL

298.

0

2,500

Bol

der C

oncr

ete

Hig

h st

reng

then

con

cret

e

500

Bol

der C

oncr

ete

Hig

h st

reng

then

con

cret

e

1,5002,500

1,80

090

065

0

EL

299.

22,000

500

850

1:0.5

1/20

EL

300.

45

200

Bol

der C

oncr

ete

7,70

0

Cro

ss S

ectio

n of

Wei

r

DL=

295.

0

1,000

EL 2

97.5

EL 2

98.0

5,20

050

0

19,4

5019

,450

Exp.

j t=

20m

mW

ater

sto

p B

=300

mm

Exp.

j t=

20m

mW

ater

sto

p B

=300

mm

PL-

9x50

0

Anc

hor B

olt

M24

x600

RBφ

100

L-12

0x12

0x8

PL-

12x5

0

PL-9

x350

PL-1

2x50

EL 3

01.5

EL

301.

3ｘ

φ13

250@

250

ｘφ1

325

0@25

0

Hig

h st

reng

then

con

cret

e

(Ben

ding

Wor

ks)

(Ben

ding

Wor

ks)

150

12

25

100

200

200

200

30

70

80

246

764

1,01

01,

000

R 6 00

3,34

0

1,00

0

Bar

scr

een

Det

ail

S=

1:2

5

130

Hig

h st

reng

then

con

cret

e

100

100

40

100 40

Ba

r sc

ree

n D

eta

ilS

=1:

25

Ste

el B

ar φ

100

1,30

0

No.5-2

2-59

00-0Ta

klai

Irrig

atio

n Sy

stem

in S

arpa

ng D

istri

ct

H=1

:200

The

Proj

ect f

or im

prov

emen

t of

Cro

ss S

ectio

n of

Wei

r

C L

DL=

300.

0

EL 2

99.0

EL

300.

0

Se

ctio

n E

-ES

=1

:200

EL

300.

42

1,000 1,000350350

EL

299.

07

600

1,50

0

32,7

80

1,85

0

100

2,45

0

1,700

Gab

ion

350

Se

ctio

n F

-FS

=1

:200

4,00

0

350 25

02,

700

3,50

0

2,000

EL

301.

5

EL 3

03.5

EL

301.

5

2,000

DL=

300.

0

Se

ctio

n G

-GS

=1

:200

1,25

0

3,000

EL

301.

5

1,000

350

25060

0

750

500

DL=

300.

0

3,500

200

Box

cul

vert

B x

H =

1.5

m x

1.0

m

8t B

lock

by

Bol

der C

oncr

ete

1,00

0 250

2,25

0

3,50

0500

350

Bol

der C

oncr

ete

t=35

0 350

Bol

der C

oncr

ete

t=35

0

EL

300.

5

1,5001,500

2,00

01:1.0

2,00

0

1 :1 .0

Cro

ss S

ectio

n of

Wei

r

3,500

Flow

Flow

1:2.

0

Bac

kfille

dby

Bol

der C

oncr

ete

Bold

er C

oncr

ete

2,500

500

Hig

h st

reng

then

conc

rete

1,000

1,000

Bol

der C

oncr

ete

2,500

2,020

1,030

4,470

8t B

lock

by B

olde

r Con

cret

e

8t B

lock

by B

olde

r Con

cret

e

1,000

No.5-3

2-60

00-0Ta

klai

Irrig

atio

n Sy

stem

in S

arpa

ng D

istri

ct

H=1

:200

The

Proj

ect f

or im

prov

emen

t of

Cro

ss S

ectio

n of

Out

let o

f Box

Cul

vert(

1/2)

3to

n Block～

Gabi

onS=1:200

Cro

ss S

ectio

n of

Out

let o

f Box

Cul

vert(

1/2)

177°

0'0"

8ton Bl

ock～

3ton Block

3ton

Block

S=1:200

S=1:200

1,500350 350

2,200

1,500350 350

2,200

Box

culv

ert

B x

H =

1.5

m x

1.0

m

Box

culv

ert

B x

H =

1.5

m x

1.0

m

Gab

ion

Gab

ion

3ton

Blo

ck

Gab

ion

EL 299.49

2°0'0"

1/15

0

1,500350 350

2,200

1,500350 600

2,450

130,

000

1,00

050

,000

3ton

Blo

ck8t

on B

lock

Box

cul

vert

B x

H =

1.5

m x

1.0

mG

abio

n

3ton

Blo

ck8t

on B

lock

3ton

Blo

ck

3ton

Blo

ck

Gab

ion

Flow

Flow

Flow

2,000

2,0002,000

No.6-1

2-61

00-0Ta

klai

Irrig

atio

n Sy

stem

in S

arpa

ng D

istri

ct

H=1

:100

The

Proj

ect f

or im

prov

emen

t of

Cro

ss S

ectio

n of

Out

let o

f Box

Cul

vert(

2/2)

Sec

tion J-J

S=1:100

EL

300.

02

Gab

ion

1,700

2,700

1,000

1,85

0

100

8t C

oncr

ete

bloc

k

DL=

297.

0

1,700

EL

299.

49

Gab

ion

1,60

0

DL=

297.

0

Box

cul

vert

B x

H =

1.5

m x

1.0

m

350

350

1,50

0 EL

298.

62

Gab

ion

Gab

ion

DL=

296.

0

C L

2,20

0

2,00

0

1:1.0

3t C

oncr

ete

bloc

k

1:0.5

1:0.5

1:0.5

Section

I-I

S=1:100

Secti

on H-H

S=1:100

Cro

ss S

ectio

n of

Out

let o

f Box

Cul

vert(

2/2)

Box

cul

vert

B x

H =

1.5

m x

1.0

m

Box

culv

ert

B x

H =

1.5

m x

1.0

m

600

350

1,50

0

2,45

0

350

350

1,50

0

2,20

0

3501,000350

1001,700

3501,000

1001,700

3501,000

1,700

2,700

1,000

1,700

2,700

1,000

350

350

200 70

0

200 70

0

1,60

0

200 70

0

2,00

02,

000

2,00

0

2,00

0

1,000

1,000

1,000

No.6-2

2-62

16,0

00

Wet masonry

GabionsWet masonry

Gabions

R=2

8.85

m

23°3

0'0"

CL=

11.8

3 m

EL 2

96.8

1(b

otto

m)

Brid

ge

68,4

70

3,000

1

1

5,00

05,

000

1'

1'

Gen

eral

Pla

n an

d N

ew O

pen

Can

al 1

(1/4

)

00-0Ta

klai

Irrig

atio

n Sy

stem

in S

arpa

ng D

istri

ct

H=1

:200

The

Proj

ect f

or im

prov

emen

t of

Gen

eral

Pla

n an

d N

ew O

pen

Can

al 1

(1/4

)

Exi

stin

g P

ipe

Cul

vert

(φ90

0mm

x 2

, L=2

.5m

)

55,9

00

1,00

0 500

2,950

Gab

ions

500

680

Gab

ions

Flow

EL

297.

81

Wet

mas

onry

1,00

0

2,500

2502,000250

2,500

3503,000350

3,700

2,80

0

750 25

0

5,00

011

,500

7,50

0

350

26,8

00

～G

abio

ns(φ

5mm

200m

m)

～G

abio

ns(φ

5mm

200m

m)

～G

abio

ns(φ

5mm

200m

m)

1,000 1,000

5,000

250

2502,000250

2,500

Gab

ions

250 250

KL

MN

OP

Flow

Flow

Out

let o

f Box

cul

vert

L=26

.8m

New

Ope

n C

anal

1

New

Ope

n C

anal

1L=

146.

2m

L=14

6.2m

1,500

1,50

0

600

2,100

760

1,140

EL

296.

81

(bot

tom

)

EL 2

96.8

1(B

ox c

ulve

rt bo

ttom

)

EL 2

95.3

1(O

utle

t of B

ox c

ulve

rt bo

ttom

)

EL

295.

11

EL 2

96.8

1

(bot

tom

)

EL

296.

81

(bot

tom

)

～G

abio

ns(φ

5mm

200m

m)

27,1

50

27,1

50

19,3

50

13,6

00

7,85

0

23,0

40

20,4

80

17,9

30

12,6

90

9,96

0

7,23

0

4,46

0

1,69

0

1,670

11,8

30 4,75

0

1/15

0

Fille

d W

ith C

oncr

ete

Gat

e80

0x80

0

Ope

ratio

n de

ck

5,00

0

27,1

50

Section N

'-N'

S=1:100

N'

N'

1,00

0

Flow

EL

297.

81

Brid

ge

Section

O'-O'

S=1:100

O'

O'

EL

296.

81

EL

296.

81

150

2500

San

d D

rain

Pip

eφ8

00

Flow

Flow

No.7-1

2-63

00-0Ta

klai

Irrig

atio

n Sy

stem

in S

arpa

ng D

istri

ct

H=1

:100

The

Proj

ect f

or im

prov

emen

t of

Gen

eral

Pla

n an

d N

ew O

pen

Can

al 1

(2/4

)

Gen

eral

Pla

n an

d N

ew O

pen

Can

al 1

(2/4

)

EL

298.

31

EL

295.

31

EL 2

96.8

1

～G

abio

ns(φ

5mm

200m

m)

～G

abio

ns(φ

5mm

200m

m)

EL 2

96.8

1

11,1

50

2,80

05,

000

1,000 350

3,200

1,000 250

EL

295.

11

Lon

gitudi

nal section of O

utlet of Box Cul

vert o

n right side

S=1:100

DL=

295.

0

136,

200

7,85

035

026

,800

750

250

1,500

3,000

EL

297.

81

EL 2

96.8

1

350

700

1,7001,500

1,5001,000500

K

350

Tie

bar

1,000

500

250

DL=

295.

0

250

5,00

05,

000

136,

200

EL

296.

81

250

750 100

EL

297.

31

EL 2

97.8

1

EL

296.

81

EL 2

98.3

1

EL

295.

31

EL 2

96.8

1

～G

abio

ns(φ

5mm

200m

m)

～G

abio

ns(φ

5mm

200m

m)

EL

296.

81

11,1

50

2,80

05,

000

1,000 350

3,000

3,200

EL 2

97.8

1

EL 2

95.1

1

250

500

750

DL=

295.

0

1,000

1,000 250

26,8

0035

0

7,85

0

EL

297.

81

700

1,7001,500

1,5001,000500

350

Gat

e80

0x80

0

LM

N

OP

Longitudinal section of Outlet of Box Culvert on left side

S=1:100

55,9

0011

,830

150

1,00

068

,470

1,000

500

250

DL=

295.

0

250

5,00

05,

000

136,

200

EL

296.

81

250

750 100

EL 2

97.3

1

EL

297.

81

EL

296.

81

55,9

0011

,830

150

1,00

068

,470

136,

200

Brid

ge2

Brid

ge2

250

250

350

250

150

3503

50

800350350

1,500

700

350

350

350

800350350

1,500

700

Flow

Flow

Flow

Flow

8,45

0

6,00

01,

500

350

10,9

0025

0

10,9

00

7,80

0

7,80

0

Out

let o

f Box

cul

vert

L=26

.8m

New

Ope

n C

anal

1L=

146.

2m

New

Ope

n C

anal

1L=

146.

2m

Out

let o

f Box

cul

vert

L=26

.8m

New

Ope

n C

anal

1L=

146.

2m

New

Ope

n C

anal

1L=

146.

2m

2,000

2,500

350

350

250

250

250

500

8,65

0

11,0

004,

750

2,80

0

2,350

1,250

2,850

1,750

1,350

Brid

ge1

Brid

ge1

D16

L=1

000

@50

0mm

Tie

bar

D16

L=1

000

@50

0mm

Tie

bar

D16

L=1

000

@50

0mm

Tie

bar

D16

L=1

000

@50

0mm

Tie

bar

D19

L=5

00 @

200m

m

1/15

0

No.7-2

2-64

00-0Ta

klai

Irrig

atio

n Sy

stem

in S

arpa

ng D

istri

ct

H=1

:100

The

Proj

ect f

or im

prov

emen

t of

Gen

eral

Pla

n an

d N

ew O

pen

Can

al 1

(3/4

)

350

350

1,50

0

EL 2

98.3

1

EL

296.

81

EL 2

95.3

1EL

295

.11

1,500

2,10

0

EL

297.

26

EL

296.

26

DL=

293.

0

350

3,00

035

0

3,70

060

0

150100

3503,200

3,550

3,300250

3,550

1,000

EL 2

96.8

13,00

035

035

0

2,850

1,500

1,000

C L

3,70

09,

000

350

350

2,350

100

EL 2

97.8

1

DL=

295.

0

2,00

0

1:1.0

2,00

0

1:1.0

2,00

0

1:1.0

～G

abio

ns(φ

5mm

200m

m)

～G

abio

ns(φ

5mm

200m

m)

Gab

ion

1,000

1,000

Gab

ions

～G

abio

ns(φ

5mm

200m

m)

Section K

-KS=1:100

Section L

-LS=1:100

Gen

eral

Pla

n an

d N

ew O

pen

Can

al 1

(3/4

)

2,20

0

3,90

0

3,90

0

800

4,00

0

2,00

0

1,000

1,0001,000

1,000

4,00

0

～G

abio

ns(φ

5mm

200m

m)

5,00

0

2,00

0

5,50

0

6,50

0

Gab

ions

～(φ

5mm

200m

m)

Gab

ions

～(φ

5mm

200m

m)

Ope

ratio

n de

ck

Sta

irs

250

250

1,00

0

750

Stai

rs

1,000

1,000

No.7-3

2-65

00-0Ta

klai

Irrig

atio

n Sy

stem

in S

arpa

ng D

istri

ct

H=1

:100

The

Proj

ect f

or im

prov

emen

t of

Cro

ss S

ectio

n of

Out

let o

f Box

Cul

vert(

2/2)

Sec

tion J-J

S=1:100

EL

300.

02

Gab

ion

1,700

2,700

1,000

1,85

0

100

8t C

oncr

ete

bloc

k

DL=

297.

0

1,700

EL

299.

49

Gab

ion

1,60

0

DL=

297.

0

Box

cul

vert

B x

H =

1.5

m x

1.0

m

350

350

1,50

0 EL

298.

62

Gab

ion

Gab

ion

DL=

296.

0

C L

2,20

0

2,00

0

1:1.0

3t C

oncr

ete

bloc

k

1:0.5

1:0.5

1:0.5

Section

I-I

S=1:100

Secti

on H-H

S=1:100

Cro

ss S

ectio

n of

Out

let o

f Box

Cul

vert(

2/2)

Box

cul

vert

B x

H =

1.5

m x

1.0

m

Box

culv

ert

B x

H =

1.5

m x

1.0

m

600

350

1,50

0

2,45

0

350

350

1,50

0

2,20

0

3501,000350

1001,700

3501,000

1001,700

3501,000

1,700

2,700

1,000

1,700

2,700

1,000

350

350

200 70

0

200 70

0

1,60

0

200 70

0

2,00

02,

000

2,00

0

2,00

0

1,000

1,000

1,000

No.7-4

2-66

00-0Ta

klai

Irrig

atio

n Sy

stem

in S

arpa

ng D

istri

ct

H=1

:200

The

Proj

ect f

or im

prov

emen

t of

New

Ope

n C

anal

2 a

nd S

edim

enta

tion

Basin

(1/3

)

New

Ope

n C

anal

2 a

nd S

edim

enta

tion

Basi

n(1/

3)

Lc

Rc

BM

2

250

roug

h ro

ad

1 1

1'

1'

Flow

Flow

3,500

250

750

750

1,000

1,000

2503,500250

4,000

2003,500200

3,900

10,3

5055

,500

10,3

5011

,800

3503,5001503,500350

7,850

2503,500250

4,000

1,00

0

3553,500355

2543,5001503,500254

350 350

250

250W

et s

tone

pitc

hing

67,6

00

Mai

nten

ance

gat

eH

x B

= 0

.5 x

1.5

5

Brid

ge

San

d D

rain

Pip

eB

x H

= 1

.0m

x 1

.0m

Wet

sto

ne p

itchi

ng

Wet

sto

ne p

itchi

ng

1:1

Wet

sto

ne p

itchi

ng

1:1

Wet

sto

ne p

itchi

ngW

et s

tone

pit c

hing

Wet

sto

ne p

itchi

ng

1:1

1:1

1:1

1:1

55,5

00

20,7

00

R=56

.85

m

CL=1

1.96

m

12°2

'55"

11,9

60

Dem

oliti

on o

f the

exi

stin

g w

all

5,00

0

5,00

05,

350

5,35

05,

000

7,658

4,210

5,890

6,090

1,50

03,

500

15,0

00

400

1,90

0

250

Sed

imen

tatio

n Ba

sin

L=37

.5m

New

Ope

n C

anal

2L=

88.1

6m

New

Ope

n C

anal

2L=

88.1

6m

500

960

30,1

00

1,5501,550

Gat

eB

x H

= 1

.0m

x 1

.0m

37,5

00

150

150

4,110

1/70

1/35

1/70

1/70

1/35.6

S=1:200

Gen

eral

Pla

n of

New

Ope

n C

anal

2

S=1:200

Gen

eral

Pla

n of

Sed

imen

tatio

n Ba

sin

No.8-1

2-67

00-0Ta

klai

Irrig

atio

n Sy

stem

in S

arpa

ng D

istri

ct

H=1

:100

The

Proj

ect f

or im

prov

emen

t of

New

Ope

n C

anal

2 a

nd S

edim

enta

tion

Basin

(2/3

)

New

Ope

n C

anal

2 a

nd S

edim

enta

tion

Basi

n(2/

3)

EL

292.

87EL

292

.55

EL

291.

95

Bol

der c

oncr

ete

EL 2

90.6

2

Exis

ting

gate

H x

B =

1.1

x 1

.15

Con

cret

e

Wet

sto

ne p

itchi

ng

1:1

1:1

Wet

sto

ne p

itchi

ng

25,7

00

10,3

50

1,00

0

11,8

00

200

1,50

020

0

15,3

50

1,00

0

1,000

250

67,6

00W

et s

tone

pitc

hing

1,90

0

645350

350

15,0

005,

150

10,1

00

U

500

W

Section R-R

-2S=1:100

EL

292.

87E

L 29

2.87

EL

293.

37

Ope

ning

1/35

1:1

Wet

sto

ne p

itchi

ng

B x

H =

1.0

m x

1.0

m

88,1

6025

700

15,3

50

350

67,6

00W

et s

tone

pitc

hing

600

710

595350

350

ST

5,35

015

000

1:1

Wet

sto

ne p

itchi

ng

1/70

DL=

290.

0

500

250

EL

294.

13

1 11'

1'

Secti

on R-R-1

S=1:100

Flow

Flow

Mai

nten

ance

gat

eH

x B

= 0

.5 x

1.5

5

150

350

350

350

350

V

Q

EL

294.

30

EL

294.

30

EL

294.

30

DL=

290.

0

Brid

ge

87,8

1035

0 350

87,4

60

5,00

05,

000

10,3

5022

01,

850

2,93

035

0

550

20,8

00

4,65

05,

350

10,8

001,

000

10,0

00

1,100

500

1,400

350

1,500

3,50

01,

500

5,00

0

1,250

1,450

1,550

9,65

0

1,750

1,830

2,050

750

750

255

255

1,600

200

1,000

500

960

960

1,250

22,1

50

2,250

500100

Tie

bar

D16

L=1

000

@50

0mm

Tie

bar

D16

L=1

000

@50

0mm

Tie

bar

D16

L=1

000

@50

0mm

T'

1:1.0

1:1.0

3,36

0

1:1.0

930

1/70

ST

QT'

UW

V

No.8-2

2-68

Section S

-SS=1:100

250

3,50

025

0

4,00

0

500 250

750

Sec

tion T

-TS=1:100

350

7,15

035

0

7,85

0

1,400 350

1,750

C L

3,50

015

03,

500

350

350

7,85

0

Section

U-U

S=1:100

250

5,70

025

0

6,20

0

500 250

750

2,77

515

02,

775

250

250

6,20

0

Sec

tion W

-WS=1:100

250

3,50

025

04,

000

500 250

750

C L C L

C L

00-0Ta

klai

Irrig

atio

n Sy

stem

in S

arpa

ng D

istri

ct

H=1

:100

The

Proj

ect f

or im

prov

emen

t of

New

Ope

n C

anal

2 a

nd S

edim

enta

tion

Basin

(3/3

)

New

Ope

n C

anal

2 a

nd S

edim

enta

tion

Basi

n(3/

3)

Section Q

-QS=1:100

250

3,50

025

0

4,00

0

500 250

750

C L

EL 2

94.1

3

1,00

03,

500

1,00

0

DL=

292.

0

Sec

tion V

-VS=1:100

250

3,50

025

0

4,00

0

500 250

750

C LBr

idge 1,

550

400

1,55

0

150

100

100100

100

100

100

750

750

550

100

200

450

20045

0

250

Sec

tion T'-T'

S=1:100

350

7,15

035

0

7,85

0

1,500 550

2,050

3,50

015

03,

500

350

350

7,85

0

C L

100

1/35

.6

Gat

eB

x H

= 1

.0m

x 1

.0m

San

d D

rain

Pip

eB

x H

= 1

.0m

x 1

.0m

1,000

200

No.8-3

2-69

(m)

Dis

tanc

e

(m)

Dis

tanc

e

260

Hor

izon

tal S

cale

1:1

000

Verti

cal S

cale

1:1

000

50m

03-1Tak

lai I

rrig

atio

n S

yste

m in

Sar

pang

Dis

tric

t

H=1

:100

0V=

1:50

0

Th

e P

roje

ct fo

r im

prov

emen

t of

Long

itud

inal

Pro

file

of

Can

dida

te S

ite fo

r P

rote

ctio

n D

ike

No.

(m)

Cro

ss s

ectio

n

Accu

mul

ate

SCAL

E H

=1:1

000,

V=1:

100

Long

itudi

nal P

rofil

e of

Can

dida

te S

ite fo

r Pro

tect

ion

Dik

e

1:10

00

1:100

(m)

Elev

atio

nR

iver

Bed

265

270

265.87 0.00265.59 2.16265.10 5.58

264.63 12.63

264.69 22.42

264.31 37.17

264.39 42.52

264.30 55.17

264.45 61.97

264.01 81.26

264.02 100.68

264.55 122.07

264.42 141.98

264.27 163.62

264.05 174.99

263.89 180.40

263.78 194.79

264.05 202.82

263.73 209.81

263.71 216.76

263.66 223.33

263.74 229.73

263.81 236.92

263.66 244.53

263.62 252.21

262.97 277.49

263.17 284.37

262.83 289.53

263.23 294.59

262.99 300.18

263.36 305.96

263.25 310.96

263.19 315.98

263.43 321.57263.31 326.02

263.13 331.75

262.85 338.47

0002.163.42

7.05

9.79

14.75

5.35

12.65

6.80

19.29

19.42

21.39

19.91

21.64

11.37

5.41

14.39

8.03

6.99

6.95

6.57

6.40

7.19

7.61

7.68

25.28

6.88

5.16

5.06

5.59

5.78

5.00

5.02

5.594.45

5.73

6.72

NO.1

NO.2

NO.3

NO.4

NO.5

NO.6

NO.7

450

3,0003,900

2,00

0

1,07

093

0

2,00

0

2,000

1,00

0

for t

he b

ed p

rote

ctio

nG

abio

ns

～(φ

5mm

20

0mm

)

Prot

ectio

n w

all

EL 2

93.0 ~

290.

0

aa

a-a

3,900

1,000 1,000

(Protection wall)

(Gabion) (Gabion)

EL 2

64.4

(U.S

)~

262.

2 (D

.S)

for t

he b

ed p

rote

ctio

nG

abio

ns

～(φ

5mm

20

0mm

)

Gen

eral

Pla

n fo

r the

Pro

tect

ion

Dik

e SC

ALE

=1:1

50

400

Fille

d w

ith b

olde

r and

san

d

L=34

0.00

m

1,0003,000

EL 2

67.4

(U.S

)~

265.

2 (D

.S)

1:1.51 :1 .5

Tem

pora

ry D

ike fo

rm

Tem

pora

ry D

ike

form

Not

e) A

t firs

t, th

e te

mpo

rary

dik

e fo

rm s

hall b

e em

bank

ed d

uly.

Seco

nd, t

he te

mpo

rary

dik

e fo

rm s

hall

be c

ut to

set

the

gabi

ons.

900

100

No.9

2-70

(m)

Dist

ance

(m)

Elev

atio

n

(m)

Dis

tanc

e

(m)

wal

l (st

art -

end

)

1:15

00

1:300260

270

280

250

Can

al B

ed

Accu

mul

ate

Can

al S

lope

Can

al S

lope

Plan

ned

Hei

ght o

f rai

sed

(m)

botto

m(s

tart-

end)

Hei

ght o

f rai

sed

Actual Plan

0.000283.0790.931283.0801.000285.0091.195285.0135.964284.678 6.024283.051

12.470283.288

86.414283.00286.488281.45592.402281.648

101.316281.610

129.644281.353129.689279.675

174.611279.280174.660277.501

193.901277.542193.941275.950201.130276.038

217.726276.090217.740274.475

246.847274.430246.881272.931

271.140272.600271.180271.424

300.893271.456

326.538271.338326.569269.684

381.344269.740381.423268.081

413.876268.180413.946266.743

463.899266.570463.964265.172

489.942265.110489.990263.577

500.450263.695

519.274263.518 519.319

261.942

290

246

Box

Cul

vert

(0.9

1m x

0.5

1m)

Link

can

al D

iver

sion

gat

e

0.0690.1954.7690.06

6.446

73.9440.0745.914

8.914

0.04544.922

44.9220.049

19.2410.04

7.189

16.5960.014

29.1070.034

24.2590.04

29.713

25.6450.031

54.7550.079

32.4530.07

49.9530.065

25.9780.048

10.46

18.8240.045

1/259 existing

1/126 1/320

1/114 1/320

1/367 existing

Reverse 1/350

1/647 existing

1/73 1/320

1/644 existing

Reverse 1/320

1/289 existing

1/419 1/350

1/106 existing

SCAL

E H

=1:1

500,

V=1:

300

Long

itudi

nal P

rofil

e of

Lin

k ca

nal (

1/2)

0.931

Reverse 1/320

Hor

izon

tal S

cale

1:1

500

Verti

cal S

cale

1:3

000

75m

00-1Ta

klai

Irrig

atio

n Sy

stem

in S

arpa

ng D

istri

ct

H=1

:150

0

The

Proj

ect f

or im

prov

emen

t of

Long

itudi

nal P

rofil

e of

Lin

k ca

nal (

1/2)

V=1:

300

B.P.

Bigi

nnin

g of

Lin

k ca

nal

BP.

+12.

5N

o.1

Dro

p

No.

2 D

rop

No.

3 D

rop

No.

4 D

rop

No.

5 D

rop

No.

6 D

rop

No.

7 D

rop

No.

8 D

rop

No.

9 D

rop

No.

10 D

rop

No.

11 D

rop

No.

12 D

rop

No.

13 D

rop

- 0.150None

- 0.2700.100

- 0.3590.100

- 0.20None

- 0.100

- 0.250

- 0.356

- 0.300

- 0.105

- 0.200

- 0.250

- 0.147

0.221

None

0.100

None

0.328

None

None

0.302

0.150

0.105

0.100

0.20

0.221

0.250

0.100

0.300

0.328

0.200

0.250

0.349

- 0.261

- 0.354

- 0.100

- 0.356

- 0.100

- 0.100

- 0.2530.100 0.159 - 0.194

No.10-1

2-71

(m)

Dist

ance

(m)

Elev

atio

n

(m)

Dis

tanc

e

(m)

wal

l (st

art -

end

)

1:15

00

1:300260

270

280

250

Can

al B

ed

Accu

mul

ate

Can

al S

lope

Can

al S

lope

Plan

ned

Hei

ght o

f rai

sed

(m)

botto

m(s

tart-

end)

Hei

ght o

f rai

sed

Actual Plan

489.942265.110489.990263.577

500.450263.695

519.274263.518 519.319

261.942 523.211262.091523.410263.636528.264

263.605

528.329262.080

548.242261.990548.296260.582554.120260.895

597.397260.607 597.463258.827

599.619258.868

650.864258.744650.873257.218

693.797257.178693.815255.724699.598255.642

739.336255.440739.380253.922

774.190253.790774.208252.141

800.149252.050

820.809251.907820.850250.412

874.700249.864 874.734

248.724 877.678248.561

900.335

248.697

973.519247.651

984.306246.934

290

246

Box

Cul

vert

25.9780.048

10.46

18.8240.0453.8920.1994.8540.065

19.9130.0485.83

43.2770.0662.156

51.2450.009

42.9240.0185.783

0.044

34.810.018

25.941

20.660.041

53.850.0342.944

17.034

31.277

10.787

1/106 existing

1/221 existing

1/150 existing

1/413 existing

1/1073 existing

1/1073 existing

1/264 existing

1/199 existing

1/98 1/320

1/50

No.

12 D

rop

No.

13 D

rop

No.

14 D

rop

No.

15 D

rop

No.

16 D

rop

No.

17 D

rop

No.

18 D

rop

No.

19 D

rop

No.

20 D

rop

No.

21 D

rop

+8.5

7+2

5.6

+67.

51+1

09.5

7

Hor

izon

tal S

cale

1:1

500

Verti

cal S

cale

1:3

000

75m

00-2Ta

klai

Irrig

atio

n Sy

stem

in S

arpa

ng D

istri

ct

H=1

:150

0

The

Proj

ect f

or im

prov

emen

t of

Long

itudi

nal P

rofil

e of

Lin

k ca

nal (

2/2)

V=1:

300

883.301

942.242

5.623

41.907

None

None

None

None

None

- 0.100

- 0.517

None

None

None

None

None

None

None

0.100

0.100

0.138- 0.479

recon-struction

(elevation)

SCAL

E H

=1:1

500,

V=1:

300

Long

itudi

nal P

rofil

e of

Lin

k ca

nal (

2/2)

+2.9

4

249.109Plan

ned

cana

l bed

1/320

1450

248.513

(drop)

248.724

1/320recon

-struction

248.513

247.063(elevation)

(elevation)

246.934(elevation)

+68.

24

942.967 0.725 (Drop)

- 0.2530.100 0.159 - 0.194

- 0.1000.100

No.10-2

2-72

DL=

276.

00

DL=

275.

00

00-1Tak

lai I

rrig

atio

n S

yste

m in

Sar

pang

Dis

tric

t

0

SCAL

E: 1

:100

5m

S=1:

100

SCAL

E =1

:100

Cro

ss S

ectio

n of

Lin

k C

anal

(1/4

)

Th

e P

roje

ct fo

r im

prov

emen

t of

Cro

ss S

ectio

n o

f Lin

k C

anal

(1/

4)

BP.+

12.5

- N

o.1

DL=

284.

500

No.

1 -

No.

2

DL=

281.

500

(Sta

rt Po

int)

DL=

281.

500

No.

2 -

No.

3

DL=

279.

500

DL=

279.

500

DL=

277.

500

DL=

276.

00

(End

Poi

nt)

DL=

283.

000

No.

5 -

No.

6

No.

3 -

No.

4

No.

4 -

No.

5

(Sta

rt Po

int)

(End

Poi

nt)

(Sta

rt Po

int)

(End

Poi

nt)

(Sta

rt Po

int)

(End

Poi

nt)

(Sta

rt Po

int)

(End

Poi

nt)

(Sta

rt Po

int)

(End

Poi

nt)

DL=

274.

00

DL=

277.

500

Stan

dard

cro

ss s

ectio

n fo

r im

prov

emen

t SC

ALE

=1:5

0

401

372

200

200

355

331

Gro

und

line

Rai

sed

up w

all

by w

et m

ason

ry

cut l

ine

C L

C m

2Exca

vatio

nB

m2

Rai

sed

up b

otto

mby

con

cret

eD

m2

(L=7

4m)

(L=4

3m)

(L=4

5m)

(L=1

9m)

(L=2

4m)

(L=2

9m)

A m

401

374

355

331

524

491

615

576

200

200

452

423

452

423

200

200

200

200

474

411

352

309

502

435

502

435

EL 2

84.6

78EL

283

.002

EL 2

81.7

48

EL 2

79.7

75

EL 2

81.6

14

EL 2

79.6

34

EL 2

77.5

80EL

277

.542

EL 2

76.2

59EL

276

.190

EL 2

74.4

75EL

274

.43

(Chipping)

1:0.5

existing

slope

U.S

U.S

D.S

U.S

D.S

U.S

D.S

U.S

D.S

U.S

D.S

No.11-1

2-73

No.

6 -

No.

7

DL=

273.

00D

L=27

3.00

No.

7 -

No.

8

DL=

271.

50

No.

8 -

No.

9

DL=

269.

50D

L=26

9.50

No.

9 -

No.

10

DL=

268.

00D

L=26

8.00

No.

10

- N

o.11

DL=

266.

50

No.

11

- N

o.12

DL=

265.

00

00-2Tak

lai I

rrig

atio

n S

yste

m in

Sar

pang

Dis

tric

t

0

SCAL

E: 1

:100

5m

S=1:

100

SCAL

E =1

:100

Cro

ss S

ectio

n of

Lin

k C

anal

(2/4

)

Th

e P

roje

ct fo

r im

prov

emen

t of

Cro

ss S

ectio

n o

f Lin

k C

anal

(2/

4)

(Sta

rt Po

int)

(End

Poi

nt)

(Sta

rt Po

int)

(End

Poi

nt)

(Sta

rt Po

int)

(End

Poi

nt)

(Sta

rt Po

int)

(End

Poi

nt)

(Sta

rt Po

int)

(End

Poi

nt)

(Sta

rt Po

int)

(End

Poi

nt)

DL=

271.

00D

L=26

6.50

(L=2

4m)

(L=5

5m)

(L=5

5m)

(L=3

3m)

(L=5

0m)

(L=2

6m)

DL=

265.

00

200

200

200

200

352

309

608

524

541

499

541

499

568

524

349

322

200

200

200

200

641

604

420

388

478

445

478

445

533

498

533

498

Stan

dard

cro

ss s

ectio

n fo

r im

prov

emen

t SC

ALE

=1:5

0

Gro

und

line

by w

et m

ason

ry

cut l

ine

C L

C m

2Exca

vatio

nB

m2

by c

oncr

ete

D m

2A

mR

aise

d up

wal

lR

aise

d up

bot

tom

EL 2

71.4

24EL

271

.338

EL 2

66.7

50EL

266

.743

EL 2

65.1

72EL

265

.110

EL 2

73.0

31

EL 2

69.8

40

EL 2

68.2

80EL

272

.956

EL 2

70.0

12

EL 2

63.3

83

(Chipping)

1:0.5

existing

slope

U.S

D.S

U.S

D.S

U.S

D.S

U.S

D.S

U.S

D.S

U.S

D.S

No.11-2

2-74

No.

12

- N

o.13

DL=

263.

5D

L=26

3.5

No.

13

- N

o.14

DL=

262.

0

No.

18

- N

o.19

DL=

254.

0

No.

19

- N

o.20

DL=

252.

0

No.

20

- N

o.21

DL=

250.

5D

L=24

9.5

00-3Tak

lai I

rrig

atio

n S

yste

m in

Sar

pang

Dis

tric

t

0

SCAL

E: 1

:100

5m

S=1:

100

SCAL

E =1

:100

Cro

ss S

ectio

n of

Lin

k C

anal

(3/4

)

Th

e P

roje

ct fo

r im

prov

emen

t of

Cro

ss S

ectio

n o

f Lin

k C

anal

(3/

4)

(Sta

rt Po

int)

(End

Poi

nt)

(Sta

rt Po

int)

(End

Poi

nt)

(Sta

rt Po

int)

(End

Poi

nt)

(Sta

rt Po

int)

(End

Poi

nt)

(Sta

rt Po

int)

(End

Poi

nt)

DL=

262.

0

DL=

254.

0

DL=

252.

0

(L=2

9m)

(L=2

9m)

(L=3

5m)

(L=4

7m)

(L=5

4m)

200

200

200

200

362

389

440

483

312

330

312

330

324

347

324

347

200

200

200

200

470

322

470

322

512

353

978

699

Stan

dard

cro

ss s

ectio

n fo

r im

prov

emen

t SC

ALE

=1:5

0

Gro

und

line

by w

et m

ason

ry

cut l

ine

(Chipping)

C L

C m

2Exca

vatio

nB

m2

1:0.5

existing

slope

by c

oncr

ete

D m

2A

m

No.

14

- N

o.18

(L=1

91m

)N

o ne

ed th

e im

prov

emen

t

Rai

sed

up w

all

Rai

sed

up b

otto

m

EL 2

62.0

80EL

261

.990

EL 2

53.9

22EL

253

.790

EL 2

52.1

41EL

251

.907

EL 2

63.7

95

EL 2

50.5

12

EL 2

63.7

12

EL 2

49.8

64

U.S

D.S

U.S

D.S

U.S

D.S

U.S

D.S

U.S

D.S

U.S

D.S

No.11-3

2-75

SCAL

E =1

:100

Cro

ss S

ectio

n of

Lin

k C

anal

(4/4

)

No.

21

00-4Tak

lai I

rrig

atio

n S

yste

m in

Sar

pang

Dis

tric

t

0

SCAL

E: 1

:100

5m

S=1:

100

Th

e P

roje

ct fo

r im

prov

emen

t of

Cro

ss S

ectio

n o

f Lin

k C

anal

(4/

4)

EL 2

49.1

05

EL 2

48.7

15EL

248

.513

DL=

248.

5

DL=

248.

5D

L=24

8.0

EL 2

48.6

97

EL 2

48.5

53

DL=

248.

0

DL=

248.

0

No.

21+2

.94

No.

21+8

.57

No.

21+2

5.6

No.

21+6

7.51 EL

247

.063

DL=

247.

0

No.

21+6

8.24

No.

21+1

09.5

7

EL 2

46.9

34

DL=

246.

5

Stan

dard

cro

ss s

ectio

n fo

r rec

onst

ruct

ion

SCAL

E =1

:50

C L

Exca

vatio

nB

m2

1:0.5

by c

oncr

ete

D m

2

Can

al b

otto

m

Wal

l by

wet

mas

onry

C m

2

Emba

nkm

ent

A m

2

Con

cret

cap

E m

2

1:0.5

(m2)

Gro

und

line

(m2)

(m2)

(m2)

(m2)

(m2)

0.14

(m2)

D.S

No.11-4

2-76

0.000294.212

2.057294.195 290.619

4.992290.6195.042295.994

HLC-2294.067

206.128294.125

230.646294.778 290.592

233.678290.592 292.075243.766292.052245.081292.407248.511292.113273.837292.009 290.842

277.320290.807 291.042

281.344289.528 289.806281.765289.803 289.732

307.149289.600 288.307310.562288.312 288.572311.080288.560 287.105314.631286.993 287.274315.183287.288 287.215

343.790287.060

346.592287.058

370.033286.918 287.038370.538287.049 285.685373.970285.636 285.918374.496285.911 285.804379.107285.793 285.846379.667285.833 285.775393.093285.509 285.664393.931285.662 283.892398.654283.831 284.053405.779284.142431.334283.927

505.788283.991

575.298283.966

587.528283.982

599.578284.024605.578283.979610.767283.979

622.550283.993

637.158283.938

705.496283.937

715.105283.964

734.105283.810738.283283.906741.521283.902

750.273283.914

763.827283.923

781.900283.877

803.962283.899

818.687283.890

828.714283.888

844.651283.830

871.890283.808

882.994283.837886.848283.850887.958283.850

904.594283.844

Accu

mul

ate

Dis

tanc

e

Elev

atio

n2(u

pper

)

Cro

ss S

ectio

nno

.

Siphon

Elev

atio

n1(d

own)

Dis

tanc

e

Gate

of S

iphon

1st S

iphon

(Inle

t)

Cros

s Brid

ge

B=2.

8m

Pipe

of A

qued

uct

Instr

umen

t Stat

ion

3.550290.619 HLC-1

HLC-3

HLC-4290.592

276.975290.811 HLC-5

232.182

305.867289.584 HLC-6

HLC-7

HLC-8

HLC-9

HLC-10

HLC-11

HLC-12

EL29

0.62

Botto

m L

evel

of S

ipho

nEL

290.

59Bo

ttom

Lev

el o

f Sip

hon

277.904291.012 289.544

1st S

iphon

(Outl

et)

1:25

00

1:250

280

285

290

295

300

305

Hor

izon

tal S

cale

1:2

500

Verti

cal S

cale

1:2

500

125m

Dra

wing

No. 03

-1SC

ALE

UN

ITRE

V.

Takl

ai Ir

rigat

ion

Syst

em in

Sar

pang

Dist

rict

H=1

:250

0V=

1:25

0

The

Proj

ect f

or im

prov

emen

t of

Long

itudi

nal P

rofil

e of

Hig

h Le

vel C

anal

(1/7

)

SCAL

E H

=1:2

500,

V=1:

250

Long

itudi

nal P

rofil

e of

Hig

h Le

vel C

anal

(1/7

)

HLC-0000

2.057

1.4420.050

100.280

24.518

1.49610.0881.3153.43025.326

0.345

3.4400.421

1.2823.4130.5183.5510.552

28.607

2.802

23.4410.5053.4320.5264.6110.56013.4260.8384.7237.12525.555

74.454

69.51

12.23

12.056.0005.198

11.783

14.608

68.338

9.609

19.0004.1783.238

8.752

13.554

18.073

22.062

14.725

10.027

15.937

27.239

11.1043.8541.110

16.636

1.493

3.138

1.536

24.102

0.584

Ref

eren

ceD

raw

ing

Rih

abilit

atio

nIte

m

1st S

ipho

n φ8

00m

m

Lege

nd

C.G

: C

heck

Gat

eD

.G :

Ditr

ibut

ion

Gat

e

Cros

s Brid

ge

B=3.

2m

Ris

en u

p w

all b

y 0.

1mL=

165.

0mR

ihab

ilitat

ion

of W

et M

ason

ry w

all

L=74

.5m

Cov

ered

by

conc

rete

L=2

05.8

m

Begin

ning

of H

igh L

evel

Cana

l

Gro

und

Leve

l

L=22

5.69

m

Inst

all t

he S

afet

y Sc

reen

x2

105.848 100.806

Inte

rval

AIn

terv

al B

300

2100

300

800

765

1650

765

3180

1700

Inte

rval

A :

Stan

dard

Sec

tion

SCAL

E 1:

100

Inte

rval

B :

Stan

dard

Sec

tion

SCAL

E 1:

100

1:0.45by

Mor

tare

dW

et M

ason

ryby

Mor

tare

dW

et M

ason

ry

No.12-1

2-77

904.594283.844

962.054283.808

973.829283.800

1006.046283.786

1008.807283.672

1012.741283.770

1049.467283.857

1062.667283.840

1070.557283.860

1076.889283.767

1107.051286.326

1161.315283.768

1170.676283.779

1183.142283.769

1198.896283.720

1215.883283.731

1231.063283.715

1270.987283.642

1302.371283.644

1305.742283.669

1317.108283.663

1335.048283.652

1346.347283.631

1380.264283.656

1409.425283.636

1432.345283.654

1450.190283.605

1461.991283.604

1478.944283.604

1508.230283.591

1529.448283.551

1529.739283.550

1530.360283.576

1540.342283.576

1543.417278.6681543.454285.261

1544.013285.261

1581.135285.136

1581.170278.8861583.866281.2671589.560283.4101598.364283.413

1599.137283.413

1607.880283.409

1626.889283.413

1645.730283.203

1658.746283.394

1661.650283.393

1699.252283.393

1710.270283.400

1725.156283.401

1743.950283.406

1762.041283.389

1775.979283.375

1796.743283.380

1809.192283.345

HLC-12

HLC-13

HLC-14

HLC-15

HLC-16

HLC-17

HLC-19

HLC-20

HLC-21

C.G.

1 2nd

Siph

on (in

let)

2nd

Siph

on (o

utlet

)

EL27

8.89

Botto

m L

evel

of S

ipho

nEL

278.

67Bo

ttom

Lev

el o

f Sip

hon

Accu

mul

ate

Dis

tanc

e

Elev

atio

n2(u

pper

)

Cro

ss S

ectio

nno

.

Elev

atio

n1(d

own)

Dis

tanc

e

1:25

00

1:250

270

275

280

285

290

295

300

Hor

izon

tal S

cale

1:2

500

Verti

cal S

cale

1:2

500

125m

Dra

win

g No

. 03-2

SCAL

EU

NIT

REV

.

Takl

ai Ir

rigat

ion

Syst

em in

Sar

pang

Dis

trict

H=1

:250

0V=

1:25

0

The

Proj

ect f

or im

prov

emen

t of

Long

itudi

nal P

rofil

e of

Hig

h Le

vel C

anal

(2/7

)

SCAL

E H

=1:2

500,

V=1:

250

Long

itudi

nal P

rofil

e of

Hig

h Le

vel C

anal

(2/7

)

16.636

57.460

11.775

32.217

2.761

3.934

36.726

13.200

7.890

6.332

30.162

54.264

9.361

12.466

15.754

10.439

15.18

39.924

31.384

3.371

11.366

17.940

11.299

39.917

29.161

22.920

17.845

11.801

16.953

29.236

21.218

0.291

0.621

9.982

3.0750.037

0.614

37.104

0.0352.6965.6948.804

0.773

8.743

19.009

18.841

13.016

2.904

37.602

11.018

14.866

18.794

18.091

13.938

20.764

12.499

Cros

s Brid

ge

B=3.

9m

L=85

mL=

7.9m

L=15

.8m

L=31

.4m

Lege

nd

C.G

: C

heck

Gat

eD

.G :

Ditr

ibut

ion

Gat

e

D.G.

1(Ex

pired

)

W x

H =

1.95

m x

1.4m

Cros

s Brid

ge

B=2.

9m

D.G.

2

W x

H =

0.5m

x 1.

5m

　φ8

00 x

2pi

pe2n

d Si

phon

L=37

.7m

Rih

abilit

atio

n of

Wet

Mas

onry

wal

lL=

20.0

mR

ihab

ilitat

ion

of W

et M

ason

ry w

all

L=29

.2m

Rih

abilit

atio

n of

Sip

hon

inle

t

Rep

lace

the

D.G

.2

BxW

xH=2

.8m

x2.8

mx6

.6m

Ref

eren

ceD

raw

ing

Rih

abilit

atio

nIte

m

Cov

ered

by

conc

rete

on

Top

(t=0.

20)

Cov

ered

by

conc

rete

on

Top

(t=0.

20)

Inst

all t

he S

afet

y Sc

reen

x2

1205.444 6.548

HLC-18

Inte

rval

BIn

terv

al B

765

1650

765

3180

1700 Inte

rval

B :

Stan

dard

Sec

tion

SCAL

E 1:

100

1:0.45

by M

orta

red

Wet

Mas

onry

Reh

abilit

atio

n of

leak

ing

at A

qued

uct

L=10

m

Reh

abilit

atio

n of

leak

ing

at A

qued

uct

L=19

m

No.12-2

2-78

1809.192283.345

1822.535283.351

1825.507283.3561835.822283.351

1867.351283.261

1880.986283.315

1898.711283.278

1909.158283.290

1913.141283.292

1950.530283.225

1981.869283.179

1996.530283.178

2009.122282.934

2034.296283.179

2057.663283.139

2061.567283.129

2101.893283.1422109.342283.101

2123.795283.121

2133.968283.121

2147.052283.111

2163.676283.084

2190.576283.107

2226.714283.149

2244.546283.190

2258.560283.139

2258.717283.138

2259.440283.145

2287.669283.174

2318.658283.180

2326.527283.172

2345.807283.123

2377.141283.101

2398.102283.080

2441.344283.053

2471.736282.9862471.985282.9852472.648282.984

2503.281282.951

2567.721282.892

HLC-21

HLC-22

HLC-23

HLC-24

HLC-25

Accu

mul

ate

Dis

tanc

e

Elev

atio

n2(u

pper

)

Cro

ss S

ectio

nno

.

Elev

atio

n1(d

own)

Dis

tanc

e

1:25

00

1:250

280

285

290

295

300

Hor

izon

tal S

cale

1:2

500

Verti

cal S

cale

1:2

500

125m

Draw

ing

No. 03

-3SC

ALE

UNI

TR

EV.

Takl

ai Ir

rigat

ion

Syst

em in

Sar

pang

Dist

rict

H=1

:250

0V=

1:25

0

The

Proj

ect f

or im

prov

emen

t of

Long

itudi

nal P

rofil

e of

Hig

h Le

vel C

anal

(3/7

)

SCAL

E H

=1:2

500,

V=1:

250

Long

itudi

nal P

rofil

e of

Hig

h Le

vel C

anal

(3/7

)

270

275

12.499

13.343

2.97210.315

31.529

13.635

17.725

10.447

3.983

37.389

31.339

14.661

26.9

36.138

17.832

14.014

0.157

0.723

28.229

30.9897.869

19.280

31.334

20.961

43.242

30.3920.2490.663

30.633

64.44

Lege

nd

C.G

: Ch

eck

Gat

eD

.G :

Ditri

butio

n G

ate

Cros

s Brid

ge

B=3.

0mCo

ncre

te C

ross

Brid

ge

B x L

= 4

.0m

x 3.

2m

Conc

rete

Cro

ss B

ridge

B x L

= 4

.0m

x 3.

2mD.

G.3

W x

H =

0.9m

x 1.

6mC.

G.2

W x

H =

1.95

m x

1.5m

C.G.

3

D.G.

4W

x H

= 1.

95m

x 1.4

m

Rep

lace

the

Brid

geR

epla

ce th

e Br

idge

12.592

25.174

23.367

3.904

40.3267.449

14.453

10.173

13.084

16.624

2569.157282.892

2596.826282.856

2639.237282.792

2639.389282.792

2640.123282.789

2643.829282.762

2713.981282.738 HLC-26

1.436

27.669

42.411

0.152

0.754

3.686

70.152

Cros

s Brid

ge

B=1.

44m

C.G.

4

D.G.

5W

x H

= 1.

95m

x 1.4

m

W x

H =

0.5m

x 1.

45m

Ref

eren

ceD

raw

ing

Rih

abilit

atio

nIte

m

Begin

ning

of L

ink C

anal

W x

H =

0.5m

x 1.

6m

Inte

rval

B

765

1650

765

3180

1700 Inte

rval

B :

Stan

dard

Sec

tion

SCAL

E 1:

100

by M

orta

red

1:0.45

Wet

Mas

onry

Reh

abilit

atio

n of

leak

ing

at A

qued

uct

L=21

m

No.12-3

2-79

2713.981282.738

2735.699282.750

2779.052282.7342779.296282.734

2779.985282.705

2840.229282.652

2851.356282.616

2867.874282.642

2893.440282.606

2911.605282.586

2940.560282.5772940.865282.577

2941.554282.576

2966.849282.549

2978.241282.5552985.704282.535

2998.208282.565

3018.513282.600

3022.666282.595

3025.486282.555

3025.707282.523

3027.240284.197

HLC-26

EL28

1.92

Botto

m L

evel

of S

ipho

nEL

280.

44Bo

ttom

Lev

el o

f Sip

hon

3251.774283.950

3251.837280.440

3252.646280.440

3253.644280.440

3253.705281.511

3254.172282.2773259.522282.2243268.750282.235

3287.641282.2503294.195282.247

3316.114282.254

3334.212282.268

HLC-27

Accu

mul

ate

Dis

tanc

e

Elev

atio

n2(u

pper

)

Cro

ss S

ectio

nno

.

Elev

atio

n1(d

own)

Dis

tanc

e

1:25

00

1:250

280

285

290

295

300

Hor

izon

tal S

cale

1:2

500

Verti

cal S

cale

1:2

500

125m

Dra

win

g No

. 03-4

SCAL

EUN

ITR

EV.

Takl

ai Ir

rigat

ion

Syst

em in

Sar

pang

Dist

rict

H=1

:250

0V=

1:25

0

The

Proj

ect f

or im

prov

emen

t of

Long

itudi

nal P

rofil

e of

Hig

h Le

vel C

anal

(4/7

)

SCAL

E H

=1:2

500,

V=1:

250

Long

itudi

nal P

rofil

e of

Hig

h Le

vel C

anal

(4/7

)

270

275

70.152

21.718

43.3530.244

0.689

60.244

11.127

16.518

25.566

18.165

28.9550.305

0.689

25.295

11.3927.463

12.504

20.305

4.153

2.820

0.221

1.533

224.534

0.063

0.809

0.998

0.061

0.4675.3509.228

18.8916.554

21.919

18.098

Lege

nd

C.G

: Ch

eck

Gat

eD

.G :

Ditri

butio

n G

ate

Cros

s Brid

ge

B=4.

2mD.

G.6

W x

H=0.

5m x

1.45

m

C.G.

5

W x

H=1.

95m

x 1.4

m

3rd

Siph

on (i

nlet)

3rd

Siph

on (o

utlet

)

　3r

d Si

phon

φ10

00 x

2Pi

pes

L=22

4.5m

Rep

lace

the

C.G

.5In

stal

l the

saf

ety

scre

en x

2C

over

ed b

y co

ncre

te o

n th

e Si

phon

3365.145282.232

3375.383282.240

3385.867282.218

3396.737282.3653396.877282.3673397.628282.3773417.096282.200

3429.483282.200

3442.530282.208

3450.849282.191

3463.236282.198

3472.858282.202

3503.193282.225

3512.478282.191

3524.527282.191

3537.295282.178

3550.323282.164

3569.174282.164

3579.315282.185

3594.394282.164

3610.971282.157

30.933

10.238

10.484

10.8700.1400.751

19.468

12.387

13.047

8.319

12.387

9.622

30.335

9.285

12.049

12.768

13.028

18.858

10.141

15.079

16.577

C.G.

6

D.G.

7W

x H=

1.95

m x

1.25

m

W x

H=0.

5m x

1.5m

Ref

eren

ceD

raw

ing

Rih

abilit

atio

nIte

m

EL28

2.52

3C

anal

Ele

vatio

nEL

282.

277

Can

al E

leva

tion

Inte

rval

BIn

terv

al B

765

1650

765

3180

1700 Inte

rval

B S

tand

ard

Sect

ion

SCAL

E 1:

100

Mor

tare

d

1:0.45

Wet

Mas

onry

No.12-4

2-80

3610.971282.157

3690.481282.143

3704.170282.121

3720.517282.130

3742.408282.127

3795.304282.109

3805.555282.109

3876.017282.083

3936.890282.084

3936.990282.084

3938.566282.071

3970.282282.019

3993.246282.069

3997.016282.054

4018.064282.0104025.465282.014

4035.758282.016

4060.057282.015

4069.962282.010

4079.341282.015

4183.277281.984

4186.890281.983

4219.766281.954

HLC-28

HLC-29

Accu

mul

ate

Dis

tanc

e

Elev

atio

n2(u

pper

)

Cro

ss S

ectio

nno

.

Elev

atio

n1(d

own)

Dis

tanc

e

1:25

00

1:250

280

285

290

295

300

Hor

izon

tal S

cale

1:2

500

Verti

cal S

cale

1:2

500

125m

Draw

ing

No. 03-5

SCAL

EU

NIT

REV

.

Takl

ai Ir

rigat

ion

Syst

em in

Sar

pang

Dist

rict

H=1

:250

0V=

1:25

0

The

Proj

ect f

or im

prov

emen

t of

Long

itudi

nal P

rofil

e of

Hig

h Le

vel C

anal

(5/7

)

SCAL

E H

=1:2

500,

V=1:

250

Long

itudi

nal P

rofil

e of

Hig

h Le

vel C

anal

(5/7

)

270

275

16.577

79.510

13.689

16.347

21.891

52.896

10.251

70.462

60.873

0.100

1.576

31.716

22.964

3.770

21.0487.401

10.293

24.299

9.905

9.379

103.936

3.613

32.876

Lege

nd

C.G

: Ch

eck

Gat

eD

.G :

Ditri

butio

n G

ate

D.G.

8

Chec

k Gat

e Re

gues

t

4232.828281.943

4244.674282.139

4248.762282.133

4390.250281.910

4413.746281.934

4444.665281.929

4469.143281.903

13.062

11.846

4.088

141.488

23.496

30.919

24.478

Cros

s Brid

ge

B=4.

1m

Ref

eren

ceD

raw

ing

Rih

abilit

atio

nIte

m

C.G.

7

D.G.

9W

x H

= 1.

95m

x 1.

5m

W x

H =

0.7m

x 1.

5m

Inst

all t

he N

ew C

heck

Gat

e

Inte

rval

BIn

terv

al C

New

C.G

.1W

x H

= 1

.95m

x 1

.20m

765

1650

765

3180

1700 Inte

rval

B :

Stan

dard

Sec

tion

SCAL

E 1:

100

675

1450

675

2800

1500

Inte

rval

C :

Stan

dard

Sec

tion

SCAL

E 1:

100

1:0.45

by M

orta

red

Wet

Mas

onry

by M

orta

red

Wet

Mas

onry

1:0.45

No.12-5

2-81

4469.143281.903

4550.351281.849

4572.685281.876

4589.552281.921

4599.086281.870

4611.759281.9114611.983281.9124612.669281.915

4613.422282.238

4673.269282.239

4693.062282.231

4713.336282.205

4725.684282.217

4743.041282.198

4772.798282.177

4790.003282.201

4799.715282.199

4856.262282.170

4866.125282.156

4902.200282.027

4903.184282.022

5063.998282.088

5067.081282.0875074.754282.037

5112.032282.041

HLC-30

Accu

mul

ate

Dis

tanc

e

Elev

atio

n2(u

pper

)

Cro

ss S

ectio

nno

.

Elev

atio

n1(d

own)

Dis

tanc

e

1:25

00

1:250

280

285

290

295

300

Hor

izon

tal S

cale

1:2

500

Verti

cal S

cale

1:2

500

125m

Dra

win

g No

. 03-6

SCAL

EU

NIT

REV

.

Takl

ai Ir

rigat

ion

Syst

em in

Sar

pang

Dist

rict

H=1

:250

0V=

1:25

0

The

Proj

ect f

or im

prov

emen

t of

Long

itudi

nal P

rofil

e of

Hig

h Le

vel C

anal

(6/7

)

SCAL

E H

=1:2

500,

V=1:

250

Long

itudi

nal P

rofil

e of

Hig

h Le

vel C

anal

(6/7

)

270

275

24.478

81.208

22.334

16.867

9.534

12.6730.2240.686

0.753

59.847

19.793

20.274

12.348

17.357

29.757

17.205

9.712

56.547

9.863

36.075

0.984

160.814

3.0837.673

37.278

Lege

nd

C.G

: C

heck

Gat

eD

.G :

Ditr

ibut

ion

Gat

e

C.G.

9

D.G.

11W

x H=

1.94

m x 1

.20m

W x

H=1.

10m

x 1.

5m

Cros

s Brid

ge

B=3.

1m

C.G.

8D.

G.10

W x

H=1.

94m

x 1.5

6m

W x

H=0.

7m x

1.52

m

5128.131282.038

5142.346282.017

5151.817282.010

5173.034282.042

5226.230282.082

5227.140282.083

5284.503281.901

2596.328281.951

5307.006281.979

5344.151281.965

5359.470281.935

HLC-31

16.099

14.215

9.471

21.217

53.196

0.910

57.363

11.825

10.678

37.145

15.319

C.G.

11D.

G.14

W x

H=1.

00m

x 0.5

m

W x

H=0.

70m

x 0.

71m

Cros

s Brid

ge

B=0.

9m

D.G.

12

W x

H=0.

70m

x 1.

35m

C.G.

10

D.G.

13W

x H=

1.0m

x 0.

5m

W x

H=0.

70m

x 1.3

5m

Rep

lace

the

D.G

.10

Rep

lace

the

C.G

.9In

stal

l the

New

C.G

.1R

epla

ce th

e D

.G.1

3R

epla

ce th

e C

.G.1

1

Ref

eren

ceD

raw

ing

Rih

abilit

atio

nIte

m

Begin

ning

of S

iphon

to H

ill at

D.S

.are

a

W x

H =

1.2

m x

1.9

5m

Inte

rval

CIn

terv

al D

675

1450

675

2800

475

950

475

1900

1500

950

Inte

rval

C :

Stan

dard

Sec

tion

SCAL

E 1:

100

Inte

rval

D :

Stan

dard

Sec

tion

SCAL

E 1:

100

1:0.45

1:0.5

by M

orta

red

Wet

Mas

onry

Wet

Mas

onry

No.12-6

2-82

5359.470281.935

5426.708281.914

5440.216281.911

5481.847281.901

5482.816281.901

5500.520281.885

5511.049281.882

5519.400281.883

5529.121281.878

5537.610281.864

5573.156281.869

5581.924281.877

5591.230281.8755597.681281.860

5672.027281.824

5724.206281.827

5725.091281.827

5796.820281.782

5824.037281.746

5840.608281.750

5851.960281.750

5871.769281.708

5896.241281.698

5897.708281.698

5924.767281.668

5971.776281.682

5995.570281.665

HLC-32

Accu

mul

ate

Dis

tanc

e

Elev

atio

n2(u

pper

)

Cro

ss S

ectio

nno

.

Elev

atio

n1(d

own)

Dis

tanc

e

1:25

00

1:250

280

285

290

295

300

Hor

izon

tal S

cale

1:2

500

Verti

cal S

cale

1:2

500

125m

Dra

wing

No. 03

-7SC

ALE

UN

ITR

EV.

Takl

ai Ir

rigat

ion

Syst

em in

Sar

pang

Dist

rict

H=1

:250

0V=

1:25

0

The

Proj

ect f

or im

prov

emen

t of

Long

itudi

nal P

rofil

e of

Hig

h Le

vel C

anal

(7/7

)

SCAL

E H

=1:2

500,

V=1:

250

Long

itudi

nal P

rofil

e of

Hig

h Le

vel C

anal

(7/7

)

270

275

15.319

67.238

13.508

41.631

0.969

17.704

10.529

8.351

9.721

8.489

35.546

8.768

9.3066.451

74.346

52.179

0.885

71.729

27.217

16.571

11.352

19.809

24.472

1.467

27.059

47.009

23.794

Lege

nd

C.G

: C

heck

Gat

eD

.G :

Ditr

ibut

ion

Gat

e

6230.896281.5916231.270281.5916231.491281.5916231.589281.591 HLC-34

6230.673281.591

6024.317281.6446031.103281.6586036.235281.6806041.669281.669

6054.814281.615

6103.069281.6266108.165281.622

6118.044281.626

6128.709281.6576129.181281.6566136.043281.6506140.539281.6456147.091281.6306152.711281.6246158.895281.607

6172.226281.603 HLC-33

0.2230.3740.2210.098

58.447

28.7476.7865.1325.434

13.145

48.2455.096

9.879

10.6650.4726.8624.4966.5525.6206.184

13.331

Cros

s Brid

ge

Cros

s Brid

ge

B=0.

9mCr

oss B

ridge

B=1.

34m

Cros

s Brid

ge

B=4.

50m

C.G.

11

D.G.

14W

x H

= 1.

00m

x 0.

5m

W x

H =

0.70m

x 0.

71m

C.G.

12

D.G.

15W

x H=

0.70

m x

0.70

m

W x

H=0.

70m

x 0.7

0mC.

G.13

D.G.

16W

x H=

0.67

m x 0

.67m

W x

H=0.

55m

x 0.5

5mCr

oss B

ridge

B=0.

5mHi

gh L

evel

Cana

l

End

of

B=1.

0m

Rep

lace

the

C.G

.11

Ref

eren

ceD

raw

ing

Rih

abilit

atio

nIte

m

Inst

all t

he N

ew C

.G.2

W x

H =

0.7

0m x

0.8

5m

Inte

rval

D

475

950

475

1900

950

Inte

rval

D :

Stan

dard

Sec

tion

SCAL

E 1:

100

1:0.5

Wet

Mas

onry

No.12-7

2-83

Tak

lai I

rrig

atio

n S

yste

m in

Sar

pang

Dis

tric

t T

he

Pro

ject

for

impr

ovem

ent o

f

Re

habi

litat

ion

Pla

n o

f Hig

h Le

vel C

anal

(1)

0

SCAL

E: 1

:50

3.75

0m

0

SCAL

E: 1

:100

Detail"a"

S=1:100

(TYPICAL SECTION OF RISEN UP WALL)

Ris

ed up wall

100

100

Chipping

(3～

5cm)

Chipping

(3～

5cm)

600

200

300

0.5

1

0.4

1

WE

T M

AS

ON

RY

(t

=30

0)

Detail"b"

S=1:50

(TYPICAL SECTION OF WET MASONRY)

Detail"c"

S=1:100

(TYPICAL SECTION OF COVERED BY CONCRETE)

4000

200

400

400

400

400

Covered by concrete

2,800

250

250 2,800 250

Detail"d"

S=1:100

(TYPICAL SECTION OF REHABILITATION OF SIPHON INLET)

2,800

250

2,800

250

5,500

2,500

2,000

4,000

4,000

350

350

350

Detail"e"

S=1:100

(TYPICAL SECTION OF PROTECTION OF EXPOSED SIPHON)

CONCRETE(21N/

mm2)

CONCRETE(21N/mm

2)

1,000

1,000

Concrete(18N/mm2)

Con

crete(18N/mm2)

Rised up wall

L=165m

L=74.5m

L=205.8m

CON

CRETE(21N/mm2)

L=45.0m

470

430

2,000 300

1:2

1:2

300

by M

orta

red

Wet

Mas

onry

Bolder concrete

Bolder concre

te

No.13-1

2-84

7.50

0m

B

H

Gate Leaf

Guide Frame

Spindle(φ

50)

Cover Concrete

Detail"f"

S=1:100

(TYPICAL SECTION OF CHECK GATE)

NO.

BH

C.G 5

1.95m

1.40m

REMARKS

Replace

C.G 9

1.95m

1.20m

Replace

C.G 1

Install

C.G 11

1.00m

0.50m

Replace

Install

Len

ght

ofGuide frame

12.1m

11.3m

5.2m

H

B

Spindle(φ

35)

Guide Frame

Gate Leaf

500

H

1:1

1:1

200

1:1

1:1

H

NO.

BH

D.G 2

0.50m

1.50m

REMARKS

Replace

D.G 10

0.70m

1.55m

Replace

Lenght of

Guide frame

7.6m

8.5m

D.G 13

0.70m

1.35m

Replace

7.7m

Detail"g"

S=1:100

(TYPICAL SECTION OF DISTRIBUTION GATE)

Tak

lai I

rrig

atio

n S

yste

m in

Sar

pang

Dis

tric

t T

he

Pro

ject

for

impr

ovem

ent o

f

0

SCAL

E: 1

:50

3.75

0m

0

SCAL

E: 1

:100

7.50

0m

0.85m

0.70m

5.5m

New

3,000

2,000

Chipping and Plas

ter(18N/mm2)

50

Detail"h"

S=1:100

(TYPICAL SECTION OF REHABILITATION OF CROSS BRIDGE)

50

50

500

1.95m

1.20m

11.3m

W

B

L30×30×4

L30

×30×

4

D12@100

Location

WB

1st Siphon Inlet

3.50m

3.10m

3.50m

3.10m

2.30m

1.70m

2.70m

1.90m

2.30m

1.70m

Detail"i"

S=1:50

(TYPICAL SECTION OF SAFETY SCREEN)

@600

1st Siphon Outlet

2nd Siphon Inlet

2nd Siphon Outlet

3rd Siphon Inlet

3rd Siphon Outlet

2.90m

2.50m

Re

habi

litat

ion

Pla

n o

f Hig

h Le

vel C

anal

(2)

L=50.0m

C.G 2

New

No.13-2

2-85

00-0Tak

lai I

rrig

atio

n S

yste

m in

Sar

pang

Dis

tric

t T

he

Pro

ject

for

impr

ovem

ent o

f

Re

habi

litat

ion

Pla

n of

Sip

hon

Plan S=1:100

FLOW

Crac

k

Pla

tePl

ate

Roa

d

Contracti

on Joint

(Painting)

Concr

ete Saddle

300

2,700

300

1,000

Reinforced Concrete Sec

tion

3,300

Plain Concrete Section

4,000

Low

Leve

l Ca

nal

(Exi

sti

ng C

ana

l)

Siphon

φ600 Ca

st Iron Pipe

C L

100600

2,100

600

100

1,050

1,050

≒1,030

1,350

1,350

300

2,700

300

2001003001,200

3001,500

200600200

1001,000

100

AA

BB

CC

Concrete Sadd

le

Supporting Beam

(I-200×

140×

9×6.1)

Low Lev

el Canal

(Existing Canal)

Section A-A

S=1:100

Leveling Concrete

Gravel(0～

40mm)

Reinforced

Concrete Section

3,300

Plain Concrete Section

4,0

00

Roa

d

Deta

il a

Siphon

φ600 Cast I

ron

Pipe

0

SCAL

E: 1

:50

3.75

0m

0

SCAL

E: 1

:100

7.50

0m

Rehabilitation Pl

an of

the Siphon

S=1:100

C L

1,6

50

375

Canal Width 3,150

375

300

3,900

300

Detail-a

A A

Profile Bridge

S=1:100

4,500

200

100

600

100

600

100

800

Lev

eling Concrete

Gravel(0～

40mm)

Expansion Joint

Elastic Filler(t=20)

Expansion Joint

Elastic Filler(t=20)

20

20

3,860

Layout of Handrail

S=1:50

3,860

300300400400

600800

130

900×

4=3,600

130

150

B B

C L

300

4,000

300

300

1,6503001,100

Canal Bottom

Handrail

Secti

on A-A

S=1:100

300

150

800

Bea

m(F-

50×6×L=4

,050)

Strut @1,000

Slab of Bridge

(L-50×6×

L=950) Section B-B

S=1:50

400400

800 600

1,400

4,600

Impro

vement Plan of t

he Cross Bridge

on Can

alS=1:100

No.13-3

2-86

Accu

mul

ate

Dis

tanc

e

Cro

ss S

ectio

nno

.

Dis

tanc

e

Ref

eren

ceD

raw

ing

Rih

abilit

atio

nIte

m

SCAL

E H

=1:2

500,

V=1:

250

Long

itudi

nal P

rofil

e of

Low

Lev

el C

anal

(1/4

)

235

240

245

250

255

260

230

243.130

242.968242.910

242.390

242.023

0.000

192.296198.854

600.641

612.919

Cros

s Brid

ge

LLC-1

1:25

00

1:250

0.000

192.2966.558

401.787

12.278

Hor

izon

tal S

cale

1:2

500

Verti

cal S

cale

1:2

500

125m

Dra

win

g No

. 03-1

SCAL

EU

NIT

REV

.

Takl

ai Ir

rigat

ion

Syst

em in

Sar

pang

Dis

trict

H=1

:250

0V=

1:25

0

The

Proj

ect f

or im

prov

emen

t of

Long

itudi

nal P

rofil

e of

Low

Lev

el C

anal

(1/4

)

Elev

atio

n

(No.0

)by

Linin

g Typ

e

Begin

ning o

f Low

Leve

l Can

al

Out L

et of

Siph

on

D.G.

1

W x

H =

1.6m

x 1.

15m

C.G.

1

W x

H =

0.75

m x 1

.0m

D.G.

2

W x

H =

1.8m

x 1.

0m

Lege

nd

C.G

: C

heck

Gat

eD

.G :

Ditr

ibut

ion

Gat

e

C.G.

2

W x

H =

0.7m

x 1.

1m

241.689 900.000 287.081

Inte

rval

A:S

tand

ard

Sect

ion

SCAL

E 1:

100

1050

1300

1050

3400

1050

by M

orta

red

Wet

Mas

onry

Inte

rval

A

1:1

1:1

No.14-1

2-87

Accu

mul

ate

Dis

tanc

e

Cro

ss S

ectio

nno

.

Dis

tanc

e

Ref

eren

ceD

raw

ing

SCAL

E H

=1:2

500,

V=1:

250

Long

itudi

nal P

rofil

e of

Low

Lev

el C

anal

(2/4

)

235

240

245

230

225

241.573 1000.000

240.594 1500.000

241.540 1007.997

241.480 1019.333

241.090 1189.811

240.915 1241.209

Cros

s Brid

ge

LLC-2

LLC-3

1:25

00

1:250

387.081

138.791

7.997

11.336

170.478

51.398

Hor

izon

tal S

cale

1:1

:250

0Ve

rtica

l Sca

le 1

:250

012

5mDr

awin

g No

. 03-2

SCAL

EU

NIT

REV

.

Takl

ai Ir

rigat

ion

Syst

em in

Sar

pang

Dist

rict

H=1

:250

0V=

1:25

0

The

Proj

ect f

or im

prov

emen

t of

Long

itudi

nal P

rofil

e of

Low

Lev

el C

anal

(2/4

)

Elev

atio

n

Lege

nd

C.G

: Ch

eck

Gat

eD

.G :

Ditri

butio

n G

ate

241.689 900.000 287.081

240.875 1800.000 135.990

240.260 1664.010

Cros

s Brid

ge

164.01

D.G.

3

W x

H =

0.7m

x 1.

05m

C.G.

3

W x

H =

1.5m

x 1.

3mD.

G.4

W x

H =

1.65

m x 1

.1m

C.G.

4

W x

H =

0.9m

x 1.

1m

D.G.

5

W x

H =

0.6m

x 0.

7m

Inte

rval

A

Inte

rval

A:S

tand

ard

Sect

ion

SCAL

E 1:

100

1050

1300

1050

3400

1050

by M

orta

red

Wet

Mas

onry

1:1

240.790 1341.209 100.000

240.766 1361.209 20.000

Rih

abilit

atio

n W

all

L=20

.00m

Rih

abilit

atio

nIte

m

1:1

250

No.14-2

2-88

Accu

mul

ate

Dis

tanc

e

Cro

ss S

ectio

nno

.

Dis

tanc

e

Ref

eren

ceD

raw

ing

SCAL

E H

=1:2

500,

V=1:

250

Long

itudi

nal P

rofil

e of

Low

Lev

el C

anal

(3/4

)

250

245

235

240

239.967 2000.000

240.025240.010 1855.732

239.900 2193.343

239.820 2196.943

1849.244

LLC-4144.268

49.2446.488

193.343

3.600

1:25

00

1:250

Hor

izon

tal S

cale

1:1

:250

0Ve

rtica

l Sca

le 1

:250

012

5mD

rawi

ng N

o. 03-3

SCAL

EU

NIT

REV.

Takl

ai Ir

rigat

ion

Syst

em in

Sar

pang

Dist

rict

H=1

:250

0V=

1:25

0

The

Proj

ect f

or im

prov

emen

t of

Long

itudi

nal P

rofil

e of

Low

Lev

el C

anal

(3/4

)

Elev

atio

n

Lege

nd

C.G

: C

heck

Gat

eD

.G :

Ditr

ibut

ion

Gat

e

239.570 2500.000 LLC-5303.057

239.298 2616.246 116.246

230

240.875 1800.000 135.990

D.G.

6

W x

H =

0.7m

x 0.

75m

C.G.

5

W x

H =

1.35

m x

1.0m

D.G.

7

W x

H =

0.9m

x 0.

9m

C.G.

6

W x

H =

1.4m

x 1.

0mD.

G.8

W x

H =

0.7m

x 1.

05m

C.G.

7

W x

H =

1.2m

x 1.

0m

Inte

rval

AIn

terv

al B

Inte

rval

A:S

tand

ard

Sect

ion

SCAL

E 1:

100

1050

1300

1050

3400

1050

950

650

950

2550

950

1:1

1:1

Inte

rval

B:S

tand

ard

Sect

ion

SCAL

E 1:

100

by M

orta

red

Wet

Mas

onry

Wet

Mas

onry

Rih

abilit

atio

nIte

m

Rep

lace

the

C.G

.5

Cle

anin

g fo

r Can

al in

side

(from

HLC

)Si

phon

to th

e Hi

ll

Rep

lace

the

C.G

.7

Rih

abilit

atio

n to

the

Siph

on

1:1

1:1

No.14-3

2-89

Accu

mul

ate

Dis

tanc

e

Cro

ss S

ectio

nno

.

Elev

atio

n

Dis

tanc

e

Ref

eren

ceD

raw

ing

SCAL

E H

=1:2

500,

V=1:

250

Long

itudi

nal P

rofil

e of

Low

Lev

el C

anal

(4/4

)

250

245

240

233.860 2901.061 LLC-6

230

235

284.815

1:25

00

1:250

Hor

izon

tal S

cale

1:1

:250

0Ve

rtica

l Sca

le 1

:250

012

5mD

raw

ing

No. 03-4

SCAL

EUN

ITR

EV.

Takl

ai Ir

rigat

ion

Syst

em in

Sar

pang

Dist

rict

H=1

:250

0V=

1:25

0

The

Proj

ect f

or im

prov

emen

t of

Long

itudi

nal P

rofil

e of

Low

Lev

el C

anal

(4/4

)

Lege

nd

C.G

: C

heck

Gat

eD

.G :

Ditr

ibut

ion

Gat

e

237.699 2700.000 83.754

Inte

rval

C

1200

1:0.5

750

Inte

rval

C:S

tand

ard

Sect

ion

SCAL

E 1:

100W

et M

ason

ry

1:0.5

Rih

abilit

atio

nIte

m

375

450

375

239.298 2616.246 116.246

D.G.

8

W x

H =

0.7m

x 1.

05m

C.G.

7

W x

H =

1.2m

x 1.

0m

(from

HLC

)Si

phon

to th

e Hi

ll

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600

200

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(t=30

0)

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REH

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L=20

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1050 300

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ATE

Gat

e le

af

SCAL

E 1:

100

Reh

abilit

atio

n Pl

an o

f Stru

ctur

e

No.14-4

2-90

00-0Tak

lai I

rrig

atio

n S

yste

m in

Sar

pang

Dis

tric

t T

he

Pro

ject

for

impr

ovem

ent o

f

Impr

ove

men

t Pla

n o

f E

xist

ing

Con

fluen

ce

Mas

onry

wa

ll

LLC

.S -0

2

Lin

k ca

nal

Gabio

ns

(New Construction)

Retaining Wall (N

ew Construction)

(to see "Detail Plan")

A

A

EL 246.92

EL 245.15

C L

▽EL 247.45

EL 245.70

3,000

4,650

7,650

550

1,750

Retaining Wall (N

ew Construction)

(to see "Detail-a,b")

Set Gabion

(New Construction)

Secti

on A-A

S=1:200

Impro

vement Plan of E

xisting Confluen

ceS=1:200

4,000

650

3,000 7,6

50

500

500

250

500

1,250

1,750 2,5

00

750

2,0002,650

4,650

1,500

800

100

500500

1,000

700

Detai

l Plan of Retain

ing Wa

llS=1:100

Handrail

(to see "Detail-g")

Gate Opening

(to see "Detail-c～ｆ

")

aFLOW

a

b b

Deta

il a-a

S=1:100

500

500

500

1,100

800

1,750

250

200100250

250

700×

700800

6001,150

3002,000

100

1,500

100

250

1,250

1,750

GL 245.70

EL

247.

45

Handrail

Spindle

Guide Frame

Lean Concrete

Grave

l(0～

40mm)

FLOW

Gate Leaf

Opening

▽EL 246.30

Detail b-b

S=1:100

Spindle

Guide Fra

me

Lean Concrete

Gravel(0～

40mm)

Handrail

2,650

2,000

100

4,650

100

200100

2501,750

3002,0001,100

700

2,150

1,000

1,500

700800

Detail-g(Handrail)

S=1:50

250

150

1,100

550550

100

Beam(F-

50×6)

Strut(L-50×

6)@<1.0m

Operation Slab

(Rein

forced Concrete)

Detail-c(

Layout

of Guide Frame)

S=1:50

Spindle

φ35

Guide Frame

(C-75×40×

4.4×

7.3)

EL 247.45

Operation Slab

Cover Concrete

Gate Leaf

▽EL 245

.70

dd

Botto

m Slab of Retaining Wall

2502501,250250800

700

700

200

700

200

1,100

200250

FLOW

Wall

Cover Concrete

Guide Frame

(C-75×40×

4.4×

7.3)

Detail d-d

S=1:50

Detail-

e(Gate Leaf)

S=1:50

Main Beam

(L-50×

6)

Sub Beam

(F-

50×6)

380

380

W=760

H=730

f f

L-50×

6

F-5

0×6

FLOW

L-5

0×6

Rubber Seal

(W=30mm @all side)

H=730

Skin Plate

(t=

6mm)

Detail f-f

S=1:40

0

SCAL

E: 1

:100

3.75

0m

0

SCAL

E: 1

:50

1.87

5m

0

SCAL

E: 1

:40

1.50

0m

0

SCAL

E: 1

:200

7.50

0m

2,000

4,650

500

2,000

Demolition of Existin

g Wall

3,500

650

200100250

100

Lean Concrete

Grave

l(0～

40mm)

2,6

502,000

FLOW

3,000

7,650

No.15

2-91

2-2-4 Implementation Plan

2-2-4-1 Implementation policy

(1) Basic item

The implementation of this Project is to be executed in the institutional framework of Japanese grant

aid. After completing overall design, provided that the said implementation is approved by Japanese

government, an Exchange of Notes (E/N) will be exchanged between the governments of both country

to shift to the Project implementing stage. The type of lump some contract is applied to the contract for

Project implementation.

In this Project, it is planned to construct integrated head works, head race, link canal, high level main

canal, low level main canal, embankment at downstream etc and to reinforce the existing gabion

revetment.

(2) Employment of local constructors

At present, local constructors exist that are run by local people, but no constructor by foreign capital

investment is found in Bhutan. As to local constructors, most of them have small-scaled ones, but

some are large-scale ones that extend their business activities mainly in the capital city, Thimphu,

holding a lot of construction machinery. However, their past performances have largely been limited in

narrow domains of work including road construction, wet masonry and revetment such as gabion

layers with poor performances on the construction of concrete structures. Accordingly, it is only

Location map of construction work on Taklai Irrigation System

Fig 2-24：Location map of construction work on Taklai Irrigation System

2-92

possible to utilize local constructors to perform a part of the construction work scheduled under this

Project including wet masonry, gabion laying etc.

(3) Necessity of dispatching engineers

Engineers and skilled workers who have sufficient knowledge and technical skill on construction work

are very few in Bhutan. To cope with such a situation, it is planned to dispatch civil work engineers

and mechanic engineers in this construction work. At the same time, it is also planned to dispatch

skilled workers to ensure the required accuracy of the work for the provision of welding, and

installation of machinery, so as to perform the designed work under the construction system with the

initiative of skilled persons.

(4) Executing system at Bhutan’s side

As far as this Project is concerned, the Project executing agency of Bhutan side, namely, Engineering

Division (ED) of Department of Agriculture (DoA) of Ministry of Agriculture and Forestry will be

responsible for the overall management of the Project, and also the local office of Central Machinery

Unit (CMU) under DoA, that of Research and Development Center (RDC), district and county offices

concerned are to participate in the Project implementation with their role-sharing.

Central

Engineering Division,

The Department of Agriculture

Project Manager

RDC

Bhur

CMU

Bhur

District

Administration

Geog

Administration

Consultant

Central

Function and Roles

Project

management and

coordination

Agricultural

research and

extension

Support WUA

regarding O&M

Function and Roles

Major

maintenance

Function and Roles

Field coordination

Project related

clearances

Security

Extension service

Stakeholder

meetings

Function and Roles

Overall Management and Coordination

of the Project

Approval on Project Implementation

Function and Roles

Field coordination

Project related

clearances

Land issues

Community

meetings

Function and Roles(Consultant)

Detailed Design

Construction supervision

Assist in Project management

Contractor

RDC: Research and Development Centre

CMU: Central Machinery Unit

WUA: Water Users Association

Project Site

Fig 2-25：Organization for the Project Implementation

2-93

2-2-4-2 Implementation conditions

(1) Attentions to be paid on the work

1) Work of head works

The construction of head works is worked in the river. Because the planned site is surrounded by

mountains it is difficult to perform the work in the lump by coffering the entire river bed. By this

reason, the construction of this facility is designed by the method of partial coffer controlling half of

the river flow with large sized sand-bags. Water sprung into the coffer is drained by submerged pumps

with a diameter φ200m (5 pumps are mobilized).

The existing maintenance road for facility management at the mountain side of the head race is used

for the entrance of vehicles for construction work and carriage of equipment/ materials, and another

access road for construction is ensured inside the river along the right side bank since flow center line

of the river in dry season runs along left side bank.

Because the scale of head works section is large, requiring large quantity of concrete to be cast per

one time of casting, thus casting work is performed by a crane commuted from the construction yard.

On the other hand, revetment blocks are provided by cast-in-place.

2) Work of culvert section of head race

The whole section of head race ranges from the head works to the inlet of first siphon at high level

main canal. Out of this section, the sub-section of about 390m from the head works consists of culvert

with steel-reinforced concrete. The planned work for head race consists of concrete work, installation

of concrete blocks gabion to the river-side and gabion layer to the excavated hill-side.

In this concern, while large amount of excavated earth is generated from the work in culvert section,

it is planned to spoil the excavated earth by carrying it with damp-trucks to the spoil yard in river-bed

around the front of the existing gabion revetment at the right bank, at downstream side of the work site.

As to the spoil yard, it has already been consulted and agreed with the counterpart organization,

however, it will again be identified with the counterpart just prior to the initiation of the work.

3) Work of open canal section of head race

Out of the total section of the head race, about 540m is the section of open canal, and out of this

section, about 170m is designed to make it reinforce concrete structure as a newly constructed section

and the existing canal section is planned to be utilized as it is for the rest of around 370m.

Nevertheless, the existing canal has to be improved by stripping off the vulnerable/ degraded part and

plain concrete is cast (t = 20cm) over the bottom floor and flank wall. In this case, concrete is planned

to be manually cast.

4) Reinforcing work for the existing gabion revetment

The planned reinforcing work for the existing gabion revetment comprises to fill back-filling

2-94

material in front of the existing structure and to install concrete revetment. In constructing this

revetment, back-hoes are used for floor excavation and concrete is cast by a crane. In this work,

gabion is laid as foot protection work in front of the revetment.

5) Work of high level main canal

Work of high level main canal consists of repair work of wet masonry revetment along the canal,

heightening of flank wall beside the canal to cope with shortage in flow section, installation of cover

concrete to prevent stones dropping from rock mass to the canal, repair of leaking part in the existing

siphons, protective work covering the exposure of the existing siphons, repair work at leakage from

the existing aqueduct, rehabilitation of a dilapidated bridge traversing over the canal, exchanging

dilapidated check-gates/ diversion gates and installation of fences to prevent falling down.

・Heightening of flank wall of the canal and repair of wet masonry

Work of heightening flank wall of the canal covers the section of 165m downstream of the

outlet of the first siphon. In this work, surface of the existing wall is stripped off about 5m

thick and cast plain concrete over the stripped part with the heightening height of 10cm by

manual casting. At the same time, the broken section of wet masonry about 75m long located

adjacent to the site of heightening is repaired to the original structure.

・Cover concrete

Cover concrete to prevent stones dropping down to the canal is to be installed over the section

about 205m starting from the outlet of first siphon to downstream. Timbering is assembled

inside the canal and reinforced concrete is cast by manual work.

・Protective work for the part of exposure of the siphon traversing beneath a river (third siphon)

Because a part of the pipe is left exposed, the part is covered with about 35cm thick plain

concrete. In this work, excavated parts at upstream side and downstream side are refilled with

boulder concrete for preventing scouring.

・Repairing work over the broken part of conveyance siphon to an upland

Conveyance siphon to an upland is made of cast-iron. Because the tube has been cracked, the

parts of fissures are closed by welding iron sheets then the entire pipe is lined with reinforced

concrete to withstand inner water pressure, thus preventing further cracking /breakage.

・Repair of leaking parts

For repairing light leakage, mortar concrete is plastered over the leaking parts. In the case of

escalated leakage, the parts are repaired by casting plain concrete from the outside of the

structure.

・Canal traversing bridges

2-95

Two canal traversing bridges with their length and width of about 4m are to be renewed by

removing them and newly reconstructing those with concrete floor at the same locations as

they are now.

6) Work of link canal

Since the canal has wet masonry structure, heightening of the flank wall beside the existing canal by

around 20cm is worked by wet masonry, accompanied with the heightening of the bottom floor inside

the canal by about 10cm (for adjusting canal gradient) that is worked with plain concrete.

7) Work of low level main canal

The existing structure is fully made use of for constructing confluence works at the starting point of

the canal（confluence point with link canal）utilizing L-shaped revetment made of reinforced concrete

that closes necessary parts.

8) Downstream embankment work

Construction/ compaction is worked by bulldozers for the downstream embankment work, by

installing concrete leaning wall as flood protection, laying gabion at its crest and rear, river-side to

prevent erosion by unexpected overflowing flood flow. In constructing retaining wall, floor is

excavated with back-hoes and concrete is cast by crane. In this work, gabion is laid in front of

retaining wall as foot protection.

(2) Items to be regarded for procurement

It is conceived that Bhutanese laborers are employed in Gelephu and around the Project site.

However, they have been oriented in a construction rush to the sites of constructing hydro-power

generation dams and other facilities, so procuring laborers becomes exceedingly difficult especially

during peak cropping season. This situation would lead to the necessity of hiring laborers from remote

areas.

2-2-4-3 Scope of works

The following shows the division of cost sharing between Japanese side and Bhutanese side in carrying

out this plan.

2-96

Table 2-32: Cost-sharing division of construction, procurement and installation

Japanese side Bhutanese side ① Integrated headworks: 1 set

･Fixed weir: 38.9m long x 1.0m high ･Downstream bed pitching work: with concrete cross-shaped blocks

8t･coupled paving, length: 27.6m ･Water gauge: 1 set of ultrasonic type

② Headrace: 1 set ･Culvert section: width:1.5m x height:1.0m x total length 358.9m ･Open Canal section: width: 2～3.5m x height: 0.5～3.2m x total

length 631.2m ･Sedimentation basin width: 3.5～7.85m x height 0.5～1.5m x total

length 37.5m ③ Reinforcement of the existing gabion revetment: 1 set ･Concrete leaning wall: height: 3.9m x total length 410m

④ Link canal: 1 set ･section of heightening: Max. heightening 0.36m x total length 654.6m ･section of the entire renewal construction: total length 109.6m

⑤ High level main canal: 1 set ･ Rehabilitation of wet masonry revetment : total length: 123.7m ･ Canal heightening: heightening height: 0.1m x total length: 165m ･ Concrete covering: total length: 205.8m ･ Mending leakage of siphons: increased thickness by reinforced

concrete 8.4m x height 5.5m.x thickness: 0.25m ･ Protection for exposed siphon pipe: total length: 45m ･ Mending leakage from aqueduct: total length: 50m ･ Installation of check gates/ diversion gates: 10 gates ･ Installation of fence to prevent falling down: 6 sites ･ Repair of broken part in siphons: lining with reinforced concrete: 1

set ･ Renewal of canal traversing bridges: 2 bridges with concrete paved

floor: (width and length: both 4m) ⑥ Low level main canal: 1 set

･ Rehabilitation of wet masonry revetment: total length: 20m ･ Check gate installation: 2 gates ･ Conffluence works: L-shape retention wall height: 2m x total length

4.7m, newly constructing gate: 1 gate ⑦ Downstream embankment: 1 set

･Concrete leaning wall : height: 3.9m x total length 340m ･ Embankment construction: width of the crest: 4.0m x height: 3.0m x

total length 340m ⑧ Provision of software component on facility operation, water

management, O/M 1 set

① To procure construction site ② Free of charge provision of land area/ borrowed

places to be used for construction work ③ Repair of access rod to the planned construction site,

notification of information on the scheduled utilization of the existing roads to local inhabitants during construction period

④ Clearance of the official requesting procedures to be submitted to and approved by offices concerned on cutting of tree stands, collection of material aggregates from river floor etc.

⑥ Extension of electric wire cable to the site managing office.

⑦ Assignment of (2 persons of) counterparts in charge in providing software component

2-2-4-4 Consultant supervision

(1) Basic principles, Attention to be paid

In performing construction supervision under this plan, attention on the following items is to be

paid:

1) Basic principles

a) To be acquainted and conscious with the contents and background of overall design and

detailed design,

b) To understand the mechanism/ system of the Grant Aid Cooperation Project,

c) To grasp the contents of Exchange of Notes（E/N）and Grant Agreement（G/A）agreed

between both countries,

2-97

d) JICA strives for smoothly promote in collaboration with the executing agency of

Bhutanese side, namely, Engineering Division (ED) of Department of Agriculture (DoA)

of Ministry of Agriculture and Forestry, Central Machinery Unit (CMU), Research and

Development Center (RDC), local administration office and District and Geog office.

e) Items to be borne by Bhutanese side agreed on in the occasion of Overall Design will

again be re-identified with Bhutanese side.

2) Attention to be paid on construction management

a) Process management

i) To identify such required procedures as custom clearance, measures on import tax

exemption accompanying with importing/ carrying in equipment/ machinery etc, and to

consult with local executing agencies including Engineering Division (ED) of

Department of Agriculture (DoA) of Ministry of Agriculture and Forestry, Central

Machinery Unit (CMU), Research and Development Center (RDC), local administration

office and District and Geog office so as not to influence on the progress of work within

construction period.

ii) Climate in Sarpang district is divided into rainy season (flooding period: 4 months, June

~ September) and dry season (8 months October ~ next May). Access route to the

Project site has several points of traversing streams on the way where traffic becomes

impossible during rainy season, thus the construction period of a dry season is

determined the period from October to next May. In this connection, since October and

May have more rainfall than other dry-season months, it is planned that earth work /

concrete work is avoided during these months as much as possible. Quality management

iii) Careful attention is to be paid to atmospheric temperature and working conditions so as

to secure quality of concrete.

b) Safety

i) To keep safety management during the construction period so that traffic accident and

electric shock accident are not happened.

ii) To establish an emergency communication network.

c) Documents

i) To properly manage such documents as drawings of approbation, construction drawings,

completion drawings, inspection records, reports on the progress of work etc.

2-98

(2) Construction/ Procurement Supervision System and Contents of Services

Services of the consultant in supervising construction include:

1) Consultations among stakeholders prior to the initiation of construction work

2) Approving service of construction drawings,

3) Supervision on the process, quality and safety management in construction work,

4) inspection of machinery, equipment prior to shipping, that of work performances, various

kinds of tests, inspection of work quality and that of completion,

5) Provision of work reports including monthly reports of the work during construction period

and

6) Issue of certification of work completion and that of payment.

As work supervision system, regularly stationing construction supervisor is responsible for overall

supervision of the entire work throughout the construction period, and construction work supervising

engineer(s) support him at the initiation as well the completion periods. Besides, local civil engineer

who supports the above cited regularly stationing construction supervisor is appointed and stationed.

2-2-4-5 Quality control plan

It is planned to perform quality control as tabulated below.

As for concrete compaction tests, the test is carried out by collecting samples by strength class,

once in every casting day.

Table 2-33: Quality management plan (Construction period)

Type of work Inspection item Method of inspection Frequency of inspection Excavation & filling Slope gradient,

degree of compactionVisual observation, measurement of size/ height, particle size, field density test

Every major part

State of soil mechanics

Visual observation Every major part Excavation bed

Width / height Measurement of size/ height Every major part Wet masonry Stone. mortar

plastering Size of stone material, sand/ cement mix rate

Aggregate Particle size tests Once Cement Identification of quality certificate Once in a month

Slump Once in the day of casting by class

Concrete Concrete

Compaction strength test( 7th and 28th)

Reinforcing bar State of steel-bar distribution

Steel bar distribution inspection Every part

Form work, timbering Position of installation, strength

Fixing position/ method Design calculation text

Every part As need arises

Structure as built As built dimension Measuring dimension Every part

2-2-4-6 Procurement plan

(1) Construction materials/ members

2-99

Domestic procurement of most general construction materials such as reinforcing bar etc is available

in Bhutan. They are planned to be procured from Phuntsholing, central marketing place where

construction materials are collected and accumulated. The following table shows division of procuring

major construction materials/ members.

Table 2-34: Division of procuring construction materials

Destination for procurement Name of materials/ members

Bhutan Japan Third country Remarks

Fine & coarse aggregates ○

Normal Portland cement ○ Difficult to procure in local market

Reinforcing bar ○ Earth filling material ○ Riprap, Masonry stone for wall ○ Crashed stone ○ Steel scaffold material ○ Veneer form ○ Diesel oil ○ Gasoline ○ Gabion ○ Gate materials ○

Water stop ○ Difficult to procure in local market, quality is regarded

Expansion joint ○ Difficult to procure in local market, quality is regarded

Rail ○ Large sacks for sand bags ○

(2) Major construction machinery

Rough terrain, concrete mixer car, crusher plant and batcher plant are not available in Bhutan, they

are procured in the third country(India) to be used in this Project.

Table 2-35: Table of procurement division

Division of procurement Type Name of Machinery Bhutan Third country

Remarks

Back hoes ○ Crawler type,0.13m3 class, 0.28 m3 class, 0.45 m3 class, 0.8 m3 class

Bulldozers ○ 15t class, 20t class Damp trucks ○ 10t loading Crane truck ○ 4t loading 2.9t hoisting Raough terrain crane ○ 16t Vibration roller ○ 0.8-1.1t class, 3-4t class Batcher plant ○ 30 m3/h Crasher plant ○ 50 m3 /day Concrete mixer car ○ 5 m3

Construction m

achinery directly used in the construction w

ork

Dynamo generator ○

(3) Carriage route

Machinery and equipment procured in Japan is transported from Japan to Calcutta Port by marine

transport, and after landing there, they are transported via Phuntsholing in Bhutan where custom office

is located, to the site in Sarpang District by truck.

2-100

On the other hand, domestic materials procured from Phuntsholing where domestic construction

materials are collected, are carried on land along the route through Thimphu and Wangdue.

Machinery and equipment also procured in India is carried on the same route from Phuntsholing.

2-2-4-7 Operational guidance plan

Basic information (supplier, detail drawing as built, etc) of newly constructed and renewed gates is

submitted Bhutan side from the Contractor, and detail method of operation and maintenance is

instructed Bhutan side from the Consultant.

2-2-4-8 Soft component (technical assistance) plan

(1) Background of planning soft components

The target facilities to be constructed in this Project as main ones covering the Project area (target

irrigation area 1,120ha) consist of (1) new construction of the integrated headworks (including river water

gauge), (2) new construction and rehabilitation of the head race, (3) reinforcing work of the existing gabion

revetment, (4) repair of the main canal (high level canal/ low level canal/ link canal) and (5) protection

works for farmland erosion (river dike). Operation and maintenance of main facilities targeted in this

Project out of the above-listed facilities are currently carried out by RDC/ CMU that is a subordinate

organization of Engineering Division (ED) in Department of Agricultural (DoA) of Ministry of Agriculture

and Forests, while that of the secondary and minor ones are managed by Water Users Associations (WUA)

of Chuzagang Geog and Sershong Geog supported by RDC Bhur engineer that have been organized in

2001.

To realize the above-mentioned Project goals in a sustainable manner, long-term utilization of the

irrigation facilities as well as equitable and proper water allocation are essential. To this end, though

the currently existing facilities have been managed by the above cited organizations by conventional

adopted method, they have been suffering from constraints/ issues of ① insufficient knowledge for

formulating plan of facility operation and maintenance and poor technical know-how to securely put

the plan into practice, ② retarded environment to train water management technicians for

accelerating effective/ rational utilization of irrigation water. Therefore, technical support by soft

component is planned to solve these issues, in addition to the rehabilitation of the existing facilities.

(2) Target of soft components

In the light of current state of facility operation and management activities as well as water

management, on the premise of that the Bhutanese side is continuously engaged in the improvement

activities even after the completion of this Project, the soft component is planned aiming at a goal;

“the stakeholders learn and master necessary knowledge for operation and maintenance of the newly

constructed and rehabilitated irrigation facilities as well as water management”.

(3) Output of soft components

Targeted output obtained by accomplishing the above mentioned goal is expected as “improved

2-101

capacity of operating and maintaining the facilities” on targeting stakeholders including staff of RDC/

CMU who are responsible for O/M and water management and those of district/ geog offices and

board members of WUC.

(4) Identification of outputs attainment

Identification of the degree of attaining the targeted output is carried out by identifying the extent of

understanding with the training record on the state of participation of the target participants as well

with a questionnaire survey after completing the training.

(5) Activities of soft components (input planning)

Table 2-36: Content of activities of soft components

Name of support program Target stakeholders Planned activities

Improved capacity of O/M of the facilities

Engineers of RDC/ CMU and district and geog offices (about 5 persons), WUC and gate keepers (about 29 persons)

(1) Understanding of capacity, structure, functions etc of new and rehabilitated facilities

(2) Provision and management of irrigation facility inventory table

(3) Formulation of annual activity plan for operation & maintenance

(4) Mastering methods of monitoring and feeding back of the above cited O/M activity plan

(5) Formulation of adequate water allocation plan (6) Provision of irrigation facility O/M manual

(6) Procurement of resources for implementation

Provision of the soft component is planned with the preview of continuous activities after

completion of this Project so that technical staff (C/P) of the Royal Government of Bhutan can take

initiative and voluntarily tackle the O/M services, and for this purpose it is important to implement the

soft component by involving them into the planned activities. To realize this, site training in the soft

component is planned as direct support by technical staff of Japanese consultant for the trainees of

mainly the targeted technical staff (C/P) of the Bhutanese government (Engineering Division of

Department of Agriculture in Ministry of Agriculture and Forests)

① Japanese expert: 1 person

The Japanese expert is assumed to have enough experiences of water management techniques and

facility operation and maintenance techniques including preventive maintenance measures, and to

be able to manage the entire services of the proposed soft component as well as the instruction for

C/P.

② Counter parts of the project executing organization（C/P）: 2 persons

An irrigation engineer belonging to Engineering Division（ED）in Department of Agricultural

and a technical staff of the local office belonging to RDC/ CMU are assumed. After implementing

the soft component, they are assumed later engaging in monitoring on the activities of WUAs and

also in additional instruction / training to the original one provided by the soft component.

2-102

(7) Schedule of soft component implementation

Since it is desirable to utilize actually rehabilitated facilities for the training, it is planned to

implement the soft component activities for about 2 months from January 2015, the month of almost

completing the construction work.

Table 2-37: Table of schedule of soft component implementation 2015

Content of Soft Component Activity January February March

1. Domestic preparatory work 2. Local preparatory work 3. Improving capacity of facility operation & maintenance (1) Understanding of capacity, structure, functions etc of new and

rehabilitated facilities

(2) Provision and management of irrigation facility inventory table (3) Formulation of annual activity plan for operation & maintenance (4) Mastering methods of monitoring and feeding back of the above

cited O/M activity plan

(5) Formulation of adequate water allocation plan (6) Provision of irrigation facility O/M manual 4. Personal assignment plan ①Japanese expert（1 person） ②C/P staff of the executing organizations（Σ3.(1)～(6)×2psns）

(8) Estimated project cost of soft components

Table 2-38: Estimated project cost of soft components

Item Project cost （thousand yen）

A Direct personal cost （Japanese consultant） 1,789

B Direct implementing cost （Japanese consultant） 1,398

C Indirect cost （Japanese consultant） 2,290

Total 5,477

(9) Outcomes of soft components

The following include in the outcomes of the soft component: ① Completion report of the soft

component ② Irrigation facility O/M manual, and these outcomes are summarized soon after the

completion thereof and submitted to the targeted WUAs, Bhutanese government and JICA.

(10) Responsibilities of the Bhutanese side

It has been agreed as a premise of the Project that the irrigation facilities rehabilitated by this

Project are operated, maintained and managed by the Bhutanese side. In fulfilling the goal of the soft

component, contents of the activities that the Bhutanese side should carry out with responsibilities

based on the afore-mentioned premise are the following:

① Assignment and participation of two staff of C/P including their expenditure in activities,

② Provision of office space (assuming RDC/ CMU Bhur in location) for the scheduled activities and

2-103

③ Continuous monitoring on the state of organizational management of WUA and provision of

relevant advices and additional training reflecting the outcome of the monitoring.

2-2-4-9 Implementation schedule

The process of the construction work of this Project is planned based on the above mentioned

“2-1-9 Construction method / procurement method”, so that the construction work can efficiently been

carried out by taking full advantage of dry seasons.

・Detailed design: about 4 months

・Bidding/ contract period: about 2.5 months

・Construction work: about 21.0 months

（the period includes from contract with sub-contractor to the work completion）

2-104

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2-105

2-3 Obligation of the government of Bhutan

Provided that this Project as the cooperation target is implemented as Japanese Grant Aid, the

outline of the project components to be borne by the Bhutanese side required for the smooth provision

of its preparatory stage, during construction period as well as the smooth operation and management

of the constructed facilities and equipment is mentioned in the following.

2-3-1 Items to be borne by the Bhutanese side on construction division/ procurement division

(1) General items

1) to provide necessary ground space / site for constructing facilities consolidated by this Project

as well as installing machinery, equipment and placing materials used in this Project,

2) to bear the required commission fee to the banks concerned based on on-going

bank-agreement (B/A) and to issue the Authorization to Pay (A/P),

3) to promptly clear the procedure required for custom clearance etc of the machinery, equipment

and materials to be carried in by this plan,

4) to exempt or to bear import taxes, excise duties, inland/ domestic taxes and other levies to be

imposed in Bhutan in procuring machinery, equipment and materials and in providing personal

services by Japanese citizens.

5) to provide Japanese citizens who provide services for implementing this project with

necessary conveniences for their entry into Bhutan for the purpose of performing the work of

the project as well for their sojourn therein,

6) to pertinently and effectively maintain and manage facilities and equipment improved/

rehabilitated by this project. Besides, to report in reply to the request of Japan, the state of

their operation and management to Japanese side,

7) to bear all the necessary expenses that is not included in the agreed Japanese Grant Aid

Cooperation (including VAT),

8) to pay proper regard to environment and social consideration in implementing this Project.

(2) Items that Bhutan should carry out before and during the project implementation

1) to securely provide the scheduled construction site,

2) to free of charge provide space or leased land for using the construction work,

3) to repair access road to the scheduled construction site and to inform the inhabitants living

around the construction sites of the use of roads for construction purpose,

4) to provide and clear procedures of obtaining permission to fell trees and collect sand/ pebble

and stones from the river as well as to take procedure of exempting royalty of quarry,

2-106

5) to thoroughly and preliminarily inform about the interruption of irrigation water supply during

the construction period to the beneficiary people by the explanation to the inhabitants etc, and

to obtain their understanding/ cooperation to the construction work,

6) to complete prior to the initiation of the construction work the extension of electricity feeding

cable to the site management office,

7) to obtain permit of construction from the concerned agencies.

2-3-2 Items to be borne by the Bhutanese side on the software component plan

In implementing the software component, the contents of activities to be carried out by the

responsibility of Bhutanese side are as follows:

① provision of two counterpart staff including their expenditure in activites,

② provision of office space (assuming CMU Bhur in location) for the activities and

③ continuous monitoring on the state of organizational management/ activities of WUAs and

provision of pertinent advices and additional training in conformity with the result of the

monitoring.

2-3-3 Environmental and social evaluation

2-3-3-1 Current situation of procedure to obtain environmental permit for this Project

As this Project include new construction of weir and rehabilitation of the existing canal, it is subject

to the application of IEE in compliance with “Processing Environmental Clearance for Irrigation

Construction Projects: A Guide for Proponents (October 2004)”. It follows that both application for

environmental permit and report on IEE has to be submitted to DoA. DoA issues the environmental

permit provided that the contents of the report of IEE satisfy the conditions for environment

conservation. In general, it takes about a month for issuing the environmental permit counting from

the date of submission of the report. The report of IEE and application for the environmental permit on

this Project has been submitted on 15th May 2012, and it is scheduled to approve them in late

September 2012.

2-4 Project operation and maintenance plan

2-4-1 Project management/ operation and maintenance system

(1) Current state of management/ operation and maintenance

Role sharing of the operation and maintenance for Taklai Irrigation System has been fixed where

RDC and CMU are in charge of the operation and maintenance for high level and low level main canal

and link canal while water user’s associations (WUA) operate and maintain the secondary canal and

downstream to the terminal.

2-107

In this system, two WUA were established in 2001, one at High Level and the other at Low Level,

and they started the utilization of these irrigation facilities. Though they were constructed in 1989,

they had not been used for 12 years due to unstable security in this area. Their experience of O/M as

organizations is thus only about 11 years, but the system of O/M has been firmly created. Major

activity of WUA is the work of O/M (elimination of dropped stones, of sand sediments and weeding

inside waterway) twice a year and for 5 days/time. In this activity, annual organization management

fee borne by an affiliated member household has been fixed at 100 Nu/ year/ household, and since

their establishment, collection rate of this fee has been kept at 100%. The collected fee has only been

spent to an allowance of water guard (annually 5,000 Nu) but in emergency cases it can be spent for

the repair of canals. As to committee members of WUA, they manage the organizations without

receiving any allowances except water guards.

In order to maintain the life of the facilities for longer period, it is necessary to take measures for

preventing conservation by applying adequate O/M for them. For this purpose, since those who are in

charge of managing the facilities should play important role, it is essential for them to master the

techniques of daily inspection and deterioration diagnosis and conservation measures (conventional

repair). Because currently staffed management system is considered sufficient to keep O/M of this

Irrigation System, management of O/M is planned for this Project without changing the hitherto kept,

existing system.

2-4-2 Operation/ Maintenance and Management Plan

As unification of weirs and connection of main canal with link canal are to be made, there arises a

concern that current method of management and O/M would fail in the planned consistent

management and O/M to the terminal canal. Therefore, in order to maintain and manage the facilities

that are newly constructed or rehabilitated by this Project as permanent ones, it is planned to provide

the stakeholders in this management system with training through soft component aiming at not only

Fig 2-26. Operation and Maintenance System

Department of Agriculture

Sarpang Dzongkhag

Sershong GeogChairman Chuzagang GeogChairman

Vice Chairman

Financial

Village Chief

Water Manager (8)

Agr. DevelopmentDivision Secretary

Vice Chairman Financial

Secretary

Village Chief

Water Manager (6)

Central Machinery Center

Water Users Committee

Water Users Association

Water Users Committee

Water Users Association

2-108

introducing preventive and conservational concept as their paradigm, but also diffusing common rule

of water management and water distribution for newly constructed irrigation system among

RDC/CMU and the whole beneficiary (WUA).

The following procedural method is proposed here to manage, operate and maintain the facilities

that are newly constructed or rehabilitated by this Project.

1) to acquire basic knowledge for maintaining function and capacity of the facilities,

2) to regularly report state of routine management, and to provide minutes of reporting,

3) to master method of proper gate operation to secure relevant water distribution,

4) to perform circular inspection and preventive conservation (stock management),

5) to collect, manage and keep information on irrigation facilities,

6) to formulate an annual O/M activity plan and to maintain monitoring/ feed back and

7) to provide a manual on O/M for the irrigation facilities

Items and contents of the inspection consisting of routine inspection and regular one are proposed in

the following table.

Table 2-40: Items and contents of the routine / regular inspection

Division Contents Person in charge Frequency

Routine inspection and maintenance work

- Unusual state of the structures of the facility (deformation, subsidence, change in color, unusual sound, unfamiliar odor etc),

- Whether abnormality found in the function of facilities to maintain water conveyance or water level or not,

- Whether influence of irrigation or facility installation takes place in the ambient environment or not,

- Whether complaints has been issued from water users or the inhabitants living around the facilities or not,

- to provide and keep records of routine inspection and O/M work and - to manage O/M cost in good order.

Persons responsible for water management in WUA, supported by RDC and CMU

Once per week

Regular checking inspection and maintenance work

- Whether water distribution/ allocation is adequately performed or not, - Whether beneficiary farmers are satisfied with irrigation services or not, - Whether routine inspection and recording of maintenance activities are

performed or not, - Whether O/M cost is managed in good order or not and - to elaborate preventive conservation measures (stock management)

RDC and CMU Twice per year

2-5 Estimated project cost

2-5-1 Estimated cost for the project

The project cost to be borne by the Bhutanese side is estimated to be about 9 million JPY, with the

broken-down items as born by the Bhutanese side based on demarcated obligations as discussed above. The

estimation was done applying the estimation conditions as indicated below.

2-109

2-5-1-1 Project cost borne by the Bhutanese side

Table 2-41: Overall project cost to be borne by the Bhutanese side Cost item Cost

Repair of the access road to the construction sites 2,500,000Nu. Extension of feeding electric cable to the site management office 2,100,000Nu. Bank commission arranged by Bank Agreement 600,000Nu.

Total 5,200,000Nu. 9.05 million yen

2-5-1-2 Cost estimating assumption

(1) Time of the estimation: February 2012

(2) Foreign currency exchange rates: 1US$＝78.24yen、1Nu =1.74yen

(3) period of construction /procurement: The period of detailed design and the construction period is

shown in the process of implementation.

(4) Others: The cost estimation is made in accordance with the system of Grant Aid Cooperation of

Japanese Government.

2-5-2 Management, operation and maintenance cost

The budget required for management, though the operation and maintenance of downstream of

secondary canal and personnel fee such as water gourd are collected from the beneficiary farm

households and fiscal budget of the state and Geog, above budget of the middle or large size facilities

concerning Taklai irrigation system are allocated by national budget directly.

The following table shows the costs of management, operation and maintenance of the targeted

facilities during the period of 2005 ~ 2011, out of which cost of repairing flood damages amounted to

2,500,000 Nu / year (≒ 17,001,971.27 / 7years) while ordinary O/M cost comes to 1,000,000 Nu /

year (≒ 5,659,914.04 Nu / 6 years) that are allocated from national budget, then surplus budget will

be returned to MoAF.

According to the table, the rehabilitation and maintenance cost of Taklai irrigation system come to

the 6 million Nu. in maximum which is 6 times as much as ordinary O/M cost, hence, to reduce the

cost concerning the flood measures is the issue These figures imply large amount of cost incurred to

mend flood damages , inflicting considerable economic burden to the country.

2-110

Table 2-42: Annual budge of CMU

Name of scheme Budget (Nu)

Expenditure incurred

(Nu)

FY. 2005 River Diversion works(Earth work) 1,499,812.00 ①

River Bank Protection works (Gabion and foundation works) 3,884,189.06 ②

1

sub-Total 5,384,001.06 FY. 2006-2007 Gaden bank protection (Length=820m of fore layers)

4,844,917.60 ③

For Irrigation 257,123.60 2

sub-Total 20,064,000.00 5,102,041.20 FY. 2007-2008 Low Level Intake protection work (Length=48m of fore (4) layers) 339,720.00 ④

For Irrigation 2,036,704.50 3

sub-Total 4,000,000.00 2,376,424.50 FY. 2008-2009 Low Level Intake protection work (Length=100.5m of fore (4) layers) 854,455.36 ⑤

For Irrigation 20,958.64 4

sub-Total 1,616,000.00 875,414.00 FY. 2009-2010 Renovate High Level main canal (Plastering works L=2,300m) 1,204,171.30

Steel gates (3 nos) 75,.000.00

Labors payment 20,000.00

5

sub-Total 1,500,000.00 1,299,171.30 FY. 2010-2011 Low Level main canal (Length=2,000m) 1,065,956.00 ⑥

High Level canal bank protection work (Length=138m) 399,081.65 ⑦

River bank protection (Length=283m of seven (7) layers of gabion wall) 5,179,795.60

6

sub-Total 7,680,000.00 6,644,833.25 FY. 2011-2012 Renovate High Level main canal (Length=1,500m) 980,000.00 7

sub-Total 1,000,000.00 980,000.00

Flooding injury Total (①+②+③+④+⑤+⑥+⑦) 17,001,971.27

Others Total (except for above items) 5,659,914.04 Grand total 22,661,885.31

Source: CMU

Though the O/M cost of the facilities incurred by flood damages will greatly be alleviated owing to

this Project, no significant change in annual, ordinary O/M cost is foreseen. The estimation of O/M

cost after the construction work under this Project is completed is difficult because of the difficulty in

forecasting future scale of flood occurrence, but it is desired the future annual cost burden is alleviated

to the intermediate level, approx. 1,750,000Nu/yr, between annual ordinary O/M cost of 1,000,000 Nu

/annum and flood damages mending cost of 2,500,000 Nu / annum. The responsibility of O/M is

CMU mainly same as so far.

2-111

Chapter 3 Project Evaluation

CHAPTER 3 PROJECT EVALUATION

3-1 Precondition

(1) Land acquisition and permission of construction

The construction works for the project is mainly divided the targeted area into close at Taklai River and away from Taklai River. As the all of around or close Taklai river is national land, land acquisition is not required though, the trimming and removal of vegetation at land for the candidate of stock yard around headworks site are responsibility for Bhutanese side.

The access road to the site during the construction period is planned to use the existing farm road though, understanding and sharing information concerning the construction works to the residence people in targeted are will be carried out by Bhutanese side again.

Regarding the permission of construction works, the quarry which is required for concrete works is planned to collect from Taklai River and other river near site and disposal area of excavated soil is planned at downstream near the construction site, which are explained and permitted verbally by Bhutanese side. All of permission shall be carried out by Bhutanese side.

Therefore, Land acquisition and permission of construction will be carried out without any problem.

(2) Secure of approval of IEE (Initial Environmental Examination)

The procedure of IEE is carried out follow 「Processing Environmental Clearance for Irrigation Construction Projects : A Guide for Proponents（October 2004）」in Bhutan. The approval of this project was issued by National Environment Committee on 2nd November 2012.

(3) Custom clearance procedure and tax exemption measure

As this project is the Japanese Grant Aid project, custom clearance, tax and any surcharges are exempted. These procedure of exemption shall be handled by the responsible agency of Bhutanese side

3-2 Necessary inputs by the government of Bhutan

As the electric power is not supply to the site, leading the electric power is required which is carried out by Bhutanese side prior to the construction works.

In addition, counter parts and related persons from concerning division for soft components activity shall be attended and the based office for this activity shall be provided by Bhutanese side.

3-3 Important assumption

The important assumptions in order to make the project effectiveness and sustainability shall be as follows;

・There would be no extreme climatic / metrological occurrences like severe drought and flood for a long period in Taklai river and target area.

・To perform the proper water distribution and operation through Link canal to the target area

・To sustain the O &M for the facility and maintain the intake facility

・There would be no drastic change of agricultural policy and irrigation policy in Bhutan

3-1

3-4 Project evaluation

3-4-1 Relevance

Project implementation under the grant aid scheme by the Government of Japan is considered justifiable with the following viewpoints.

(1) Targeted beneficially people

The number of beneficiaries is approximately 4,300 while household is 530. The farmer's income in this area is approximately US$ 390 (17,700 Nu ) per household. While GNI (Gross National Income) is US$ 2,070 per person in Bhutan, is means that the target area’s income is approximately one-fifth of national level. The farmers account for the majority of population in the area, therefore almost people are considered at the lower level than national level in Bhutan. Accordingly, the number of poor is higher in this area.

(2) Relationship of long term development plan

In the 10th five-year national development plan for Bhutan, the target was to reduce the ratio of poverty from 23.2 % (2007) to 15%. In addition, as there are many poor people in the rural area, rural integrated development is categorized as one of the important area for development. In addition, increase in self-sufficiency of crops is an urgent issue due to the geological condition in Bhutan therefore the aim is to increase self-sufficiency from 50% of the current rate to 59 % until 2018.

The largest irrigation system in Sarpang District in Bhutan, the Taklai irrigation system, considered as the productive crucial are in south Bhutan, is expected to contribute to the improvement of national self -sufficient of rice and agricultural production in this area with the expansion of cropped area in dry season by restraining of irrigation system facility.

The 11th five-year national development plan also plans in preparation to improve agricultural infrastructure, expansion of the irrigation area and increase farmer's income, hence the implementation of this project is expected to become a model project on agricultural development in Bhutan.

(3) Relationship of Japanese grant aid scheme and policy

A mutual concern between Bhutan and Japan, since the establishment of diplomatic relations on 28th March in 1986, is to have structured friendly relations through the exchanges between imperial and royal family and economic support such as instruction of agriculture promotion. Therefore Japan is considered as country that can provide ODA support and assistance to Bhutan, while Bhutan is considered as the important for Japan as it provides support and espousal on election or resolution at international agency to Japan.

The major emphasis for Bhutan based on Japanese policies are as follows; ① Agricultural and rural development (mechanization of agriculture, improvement of agricultural infrastructure ), ②Improvement of economic foundation (road networks, electrification of rural area, diffusion of information ), ③Social development (strengthening of the educational service, strengthening of medical and health services, development of human resources for the job creation), ④ Good governance (decentralization). In this project, ① Agricultural and rural development (mechanization of agriculture, improvement of agricultural infrastructure) are included as part of the project therefore the project conforms to policy of Japan.

3-2

In addition, according to the achievement of Millennium Development Goals (MDGs) of United Nations (UN), support to “Human security" is a crucial policy that is being promoted. The project also promotes the development and improvement of agricultural productivity to increase crop self-sufficiency The Project therefore contribute to the policy " Eradicate Extreme Poverty & Hunger" which is one of the development policy on MDGs,

Bhutan advocates Gross National Happiness (GNH) as the central priority for the national plan, which does not pursue the physical or economic improvement but spiritual improvement.. This idea is focused as though it would overcome a deadlock and cooped-up feeling of the society which has given priority to development of economical efficiency, and the examination in order to introduce the idea of GNH into a new indicator for MDGs is beginning at UN, now. Accordingly, to contribute the national policy based on GNH in Bhutan expects to contribute the achievement of MDGs.

3-4-2 Effectiveness

The expected impact of the implementation of the project is as follows;

･ Quantitative effects Table: 3-1 Indicator for the Quantitative effects

Items Base year（2012） Target year（2018） Remarks Irrigation water supply in dry season

0 m3/s max. 2.24 m3/s *1) enable to supply irrigation water by construction of head works

Irrigation area 883 ha max. 1,120 ha*2) enable to supply irrigation water by rehabilitation of damaged siphon

Paddy area in dry season

10 ha 560 ha

expand the double crop area by supplied stable water in dry season. as the condition of assumptions, the cropping pattern of irrigation area in dry season is divided to vegetable and rice by a half respectively.

Annual maintenance cost

ave.3,500,000 Nu 1,750,000 Nu alleviation of rehabilitation works for the headrace canal and protection wall by gabions

※Target year is three years later after the construction

*1) Maximum planned irrigation water is considered of probability that drought discharge of Taklai river by

examined probable rainfall might be lower than planned irrigation water, 2.24 m3/s.

*2) Actual registered house hold and beneficiaries is approximately 530 and 4,300 respectively. Those are

expected to receive the benefit directly.

･ Qualitative effects

① The farmer's income will increase with the increase in rice production and better selling price.

② With the inclusion of soft component activity, there will be improvement of O &M skills and techniques. Also, collection of data and sharing of information will contribute to keep the good condition of the irrigation facility.

③ O & M activities in Taklai irrigation system will be good model and extended to other similar area.

④ through extension of rice double crop, the operating rate of machine for agricultural works which is not used during fallow periods will increase.

⑤ The direct effect of disaster prevention for irrigation area or facility will be expected by

3-3

construction of river dike; in addition, reinforcement of existing protection wall and new construction of intake or delivery canal with good durability will bring the stabilization of irrigation facility on flood period and, accordingly, contribute to raising up rice production and farmer's income.

3-4