FONERWA

RAIN WATER HARVESTING

TECHNICAL BRIEF

DRAFT

July August 2015

Prepared by:Gerard Hendriksen

Technical brief Rain Water HarvestingSummary

1.1 IntroductionThis technical brief has been developed to support the FONERWA applicants and the program’s management in the formulation and the evaluation of project proposals for rain water harvesting. The note is intended to provide information on the current state of harvesting and storing of rain water collected from roofs from private houses and public buildings. This note is not designed to restrict the options for roof rainwater harvesting proposals but instead it should help all concerned parties to provide basic information on the various water harvesting systems and to help justify choices for any selected options. In the case of new developments and innovations, it helps to compare with known solutions and to provide justifications for alternatives and new approaches.

1.2 Access to water in RwandaThe Third Integrated Household Living Conditions Survey (EICV3) of 2011 reports that 74.2% of the population in Rwanda has access to an improved source of drinking water (urban 86.4% and rural 72.1%). The Government wants to reach 100% by 2018. The EICV reports that 0.4% of the population uses rainwater as main source of drinking water. The RNRA baseline survey carried out in 2013 for their RWH project interviewed over 1200 users (households and businesses) and reports that 28.6% of the population is using rainwater as their source of water. The reason for this large difference between the two surveys is not clear and requires further investigation. For instance the RNRA Baseline study includes those the large number of households and public buildings which use jerricans, a very simple application of RWH.

Rwanda’s water and sanitation policy recommends rain water harvesting as a complementary source of water and recommends it in areas that could otherwise only be supplied by pumping at excessive costs (e.g. hilltop locations, lava region). The policy mentions that rain water harvesting cannot fully replace normal water supply systems especially during dry seasons. Districts have include RWH in their Development Plans. For instance Kicukiro has a target to achieve 100% of new buildings and 80% of existing buildings with RWH facilities by 2018, while Rubavu intends to reach 46,125 RWH systems installed by 2018 from 290 in 2012.

The MININFRA feasibility study of rainwater collection systems on public buildings in Kigali City and other towns in Rwanda was carried out in 2010. The study covered 777 buildings (divided in high rise, large and small public buildings) which needed rain water collection systems. The study provides much details of the different designs and estimates an investment of Rwf 28 billion to equip all identified public buildings with rain water storage systems.

1.3 Rain water harvesting The AfDB defines water harvesting in its broadest sense as the "collection of runoff for its productive use". It includes run off be from rooftops for domestic use, from slopes for irrigation and in situ through terracing, soil conservation techniques etc. In this technical note the focus is on domestic use of collected rain water.

WaterAid in its Technical Brief points out that rain water harvesting is a relatively simple technology and can be constructed using locally available materials and skills. Maintenance is simple and costs are low. The collected rain water can be consumed without treatment provided that a clean surface is used for collection. It provides a supply of safe water close to homes, schools and clinics.

In the case of Rwanda, the benefits of RWH to the users include:

[1)] Reduction of time required for collecting water . Surveys show that on average household spends 29 minutes per day on fetching water in rural areas and 9 minutes in urban areas. In the case of domestic RWH these time requirements are reduced to zero. It also reduces possible back injuries caused by carrying the heavy loads.

[2)] Reduction in costs of buying water from WASAC. The RNRA baseline survey found an average costs of Rwf 45 per jerrican and a total expenses of Rwf 2,920 per month (about 2 jerricans per day). If RWH delivers all the daily water requirements, the annual savings would be about Rwf 35,000 for an average household.

[3)] Availability of additional water which can be used for domestic purposes but also opens opportunities for increased household gardening, livestock care, etc.

[4)] Health benefits of additional water supply as it may influence hygiene.

Erosion control is mentioned as one of the positive impacts of RWH because of reduced run off from roofs. There are however no clear measurements in place to assess these impacts. Rain water collected and stored from the roofs of buildings in only a fraction of the rainfall and the effects during heavy downpours may be limited. For instance the total storage capacity expected to be added through the RNRA project (65,250 m3) is less than 1% of the average monthly rainfall in the project area.

Impact on WASAC is not obvious. The company will lose revenue from water sales as RWH spreads but at same time there will be a reduction in operating costs, for instance less electricity needed for the pumping stations. On the other hand, WASAC needs to ensure water for the population over the full year, including the dry season when domestic tanks run dry. It will therefore have to continue to invest in the expensive infrastructure while losing some of its revenue.

2.1 RWH systems, water demand and storage capacityRoof-top RWH systems have basically four elements:

[1)] A collection/catchment area; usually the roof of the building and in most cases in Rwanda this is made out of iron sheets. The roof is already part of the building and there no new investment needed for the rain water collection. For some larger and public buildings the roofs are flat and made out of concrete, for most houses and small building the most popular system is iron sheets on an angled roof which facilitates rain water collection.

[2)] A conveyance system consisting of gutters and pipes;[3)] A storage facility (masonry reservoir, plastic tank, jerricans etc)

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[4)] A delivery system consisting of a tap in the most simple applications or piping and pumps in larger dwellings.

One of the critical issues in RWH is to determine the user’s demand and the capacity of the storage reservoir, which is the most expensive part of that RWH system. This is especially critical for the dry season in Rwanda from June to mid-September when rainfall is very low at around 10 – 40 mm average per month. Water Aid in its technical note estimates the costs of the reservoir to be 90% of the total investments. It is therefore important to carefully match the size of reservoir with the water demand and financial capacity of the user. If the reservoir is too small, the user will have to face periods where he/she has to buy or collect water from other sources (WASAC, well, stream etc). On the other hand, an oversized reservoir will increase the investments costs. This is especially true for larger reservoirs constructed out of bricks/ stones. The popular prefabricated plastic water tanks can be changed and added at a later stage at relatively low extra costs.

The AfDB water harvesting handbook uses a simple calculation model to determine the required storage capacity:

Recommended storage capacity: Dry days multiplied by daily HH demand

The handbook estimated daily household demand at 25-40 litres/person/day. The table below provides an indication of how the water is used on a daily basis.

Table S1: Daily water demand per personPurpose Litres/person/dayDrinking only 3 - 5Cooking 4 - 5Washing dishes 3 – 5Personal hygiene 5 - 10Washing clothes 10 - 15Total 25 - 40Source: AfDB Water harvesting handbook

Based on these simple figures, the total storage capacity for a household of five persons would be between 4 – 5 m3 to last for one month. However, these figures are only indicative and are influenced by local rainfall patterns, family’s preference and other uses of water for livestock (one dairy cow requires about 20 litres of water per day) and homestead gardening for instance.

For large public buildings the MININFRA RWH study of 2010 recommends a software package (RainCycle) which takes into account the rainfall data, daily demand of water, type and size of roof, and number of days acceptable without rain water.

2.2 Costs of storage reservoirs, gutters and pipingThe table below provides basic information on sizes and costs per unit of cubic meter for the different types of reservoirs that are commonly used for RWH both in large public buildings

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as well as domestic houses. Basically the reservoirs can be divided into those constructed in situ and the pre-fabricated tanks which can be bought from hardware dealers, installed in short time and removed/ replaced/ added if needed.

Table S2: Types of reservoirs and their main characteristics

Description Storage Costs range

In si

tu Ferro cement tanks 10 – 100 m3 150 – 200,000/m3Brick/masonry tanks 5 – 30 m3 150,000 /m3Artisanal tank with 6 m3 20,000/m3

Pre

fab Metal tanks 1 – 10 m3 160,000 / m3

Fibre glass tanks 2 – 75 m3 220,000/ m3Polyethylene tanks 0.5 – 10 m3 130,000 /m3Jerricans 20 litre 125,000/m3

Adapted from RNRA Project Document and MININFRA RWH study of Public Buildings

The polyethylene tanks (mostly black in colour) have become the popular choice over the last years and have practically taken over from the metal and fibre glass tanks. Used jerricans remain the preferred option for many low income households as well as in public places, according to the RNRA baseline survey, probably because of their low costs and the possibility to start small and scale up when more money is available.

The RNRA project provides some information on the costs of gutters. The most popular systems use plastic or metal gutters ranging from Rwf 6,000 to 8,500 per meter length. Some people opt for the cheaper option of cutting and bending iron roofing sheets and these are estimated at Rwf 4,500 per meter.

3.1 RWH for public buildingsMININFRA’s feasibility study of rainwater collection for public buildings provides much technical information on the various systems. There are also annexes with bill of quantities for sample RWH systems and plans for the storage tanks. The study estimated that would require an investment of Rwf 28 billion to equip all 777 identified public buildings with rain water storage systems. The main characteristics of these RWHs are given in the following table.

Table S3: Type of RWH for public buildings and their main elements

Type of public building RWH main elementsHigh rise buildings

(17 reported)

Roof area 500 – 1,000 m2

Flat roofs, cemented Underground reservoirs Pump to bring water to header tank on the roof Average costs Rwf 50 m

Large buildings

(380 reported)

Roof area 1,200 to 6,000 m2

Iron sheet roofs Schools, health centres, markets, district offices Large storage; under of above ground

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Water pumped back to roof tank or direct through pipe network

Average costs Rwf 65Small buildings

(380 reported)

Roof area 100 – 500 m2

Iron sheet roofs Above ground tanks: cement or plastic Average costs Rwf 10 m

3.2. RWH for domestic housesThe costs for a RWH harvesting systems for individual houses depend on factors such as the size of the reservoir, type of materials for the reservoir, type and quality of the gutters and pipes used to connect to the tank and the installation of filter and other accessories. The RNRA estimates the costs of a 5 m3 storage tank for a domestic system to be Rwf 500,000 including installation. The project provides a subsidy of Rwf 150,000 and households are facilitated in getting bank credit. A similar approach is applied for smaller reservoirs of 2 – 3 m3 and subsidy is proportional to the size. The costs for gutter, pipes and other accessories are not included in the project.

The table below provides the estimated costs for a complete RWH for a house with a floor space of 120 m2. The costs are for reservoir and gutters are based on unit prices from the RNRA project.

Table S4: Cost Estimate for complete 5 m3 RWH for household

Description Unit Quantity Total Rwf %House dimensions m 8*15 =120 m2Reservoir capacity m3 5Costs of reservoir Rwf/m3 90,000 450,000  63%Length gutter m 30Costs gutter Rwf/m 7,000 210,000  33%Accessories Rwf 50,000 7%Estimated total costs Rwf 1,050,000 100%Source: own calculation using RNRA unit costs

3.3 RWH communal systems Communal water systems have been constructed (or proposed) in a number of new settlements in Rwanda (for instance Green Village of Muybe in Muhanga and Kimonyi village in Musanza). Rain water is collected from the roofs of the individual houses and conducted with pipes to the lower end of the village where it runs through a sand/gravel filter before entering in the underground reservoirs. The total capacity of the reservoirs in Muyebe is reported to be 1500 m3 which is 15 m3 per household. In the Kimonyi village the storage reservoir for 150 households will be 1500 m3 which is 10 m3 per household. The costs per household were estimated to be Rwf 2.2 – 2.5 m. This system is more expensive than using individual plastic water tanks for each household. Advantages include better filtration systems but maintenance and management will require collective efforts. Also there will be a need to carry the water from the central reservoir back to the houses up the hill, mostly done by women and girls.

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Table S5: Overview of most common options for water storage

Description Main usage Materials Costs rangeRwf/ m3

Pros Cons

In si

tu

Ferro cement tanks10 – 100 m3

Public buildings/ large houses

Gravel, sand, cement and steel bars

150 – 200,000/ m3

Long life

Costly Good skill levels needed Cannot be moved

Brick/masonry tanksfrom 5 – 30 m3

above ground

Public buildings and large houses

Stones/ blocks/ cement

150,000 /m3 Long life Known technology, Easy to repair

High investment costs Cannot be moved

Under ground10 – 50 m3

As above As above As above Saves space As above

Artisanal tank6 m3

Households in rural areas

Bricks, cement, plastic lining

20,000/m3 Relatively low costs Proven technology in

some rural areas Local artisans and

construction materials Easy to repair

Requires space Dirt can enter more easily

than for closed reservoirs Cannot be moved

Pre

fabr

icat

ed

Plastic tanks0.5 – 10 m3

All types of users, sizes according to needs

Moulded plastic, polyethylene

130,000 /m3

*) note

Widely available Quick installation Can be expanded easily Can be moved

Too costly for many households

Entry level investments much higher than for jerricans

Large to transport Requires foundation slab

Jerricans 25 litre Domestic/ small commercial

Plastic 125,000/m3 Low entry barriers Flexible Start small, scalable Can be sold

Labour intensive Requires storage space Theft Cleaning difficult

Adapted from RNRA Project Document and MININFRA RWH study of Public Buildings *) Note: in a recent conversation with RNRA the price of a 5 m3 PE tank was claimed to be Rwf 450,000

TECHNICAL BRIEF WATER HARVESTING TECHNOLOGYTable of Contents

1 INTRODUCTION....................................................................................................................... 3

1.1 Background of the note........................................................................................................................ 3

1.2 Government policies on access to drinking water and the role of RWH..................................................3

1.3 Definition of water harvesting..............................................................................................................4

1.4 Benefits of rainwater harvesting........................................................................................................... 4

2 VOLUME OF RWH STORAGE RESERVOIRS......................................................................5

2.1 Determination of size of storage reservoir............................................................................................5

2.2 Rainfall patterns................................................................................................................................... 7

2.3 Daily Water demand............................................................................................................................. 7

2.4 Some findings of the RNRA baseline survey...........................................................................................8

3 COSTS OF RWH TECHNOLOGIES........................................................................................8

3.1 Investments costs for reservoirs...........................................................................................................8

3.2 Costs of water collection system......................................................................................................... 10

3.3 Other accessories................................................................................................................................ 10

4 RWH APPLICATIONS........................................................................................................... 10

4.1 RWH for households........................................................................................................................... 104.1.1 Typical domestic system using plastic water tanks............................................................................104.1.2 Domestic systems using low costs storage reservoir.........................................................................114.1.3 Financial Benefits..............................................................................................................................12

4.2 RWH for Communal Systems............................................................................................................... 12

4.3 RWH for public buildings..................................................................................................................... 13

5 RWH FOR IRRIGATION PURPOSES.................................................................................14

Annexes Annex 1; List of publications on RWH Annex 2: Costs tables of RWH systemsAnnex 3: Access to water; EICV3 and RNRA baseline data

Abbreviations

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1 Introduction 1.1 Background of the noteThis technical brief has been developed to support the FONERWA applicants and the program’s management in the formulation and the evaluation of project proposals for rain water harvesting. The note is intended to provide up to date information on the current state of harvesting and storing of rain water collected from roofs from private houses and public buildings. This note is not designed to restrict the options for roof rainwater harvesting proposals but instead it should help all concerned parties to provide basic information on the various water harvesting systems and to help justify choices for any selected options. In the case of new developments and innovations, it helps to compare with known solutions and to provide justifications for alternatives and new approaches.

This information in the note was collected through a desk study and draws much from the MININFRA feasibility study for rainwater harvesting in public buildings1 and the RNRA project document2 and baseline study which contain much details on the different technologies, their applications, costs and benefits. This was further checked against internet sites from international sources such as WaterAid3 and Practical Action.

The results and views presented in this report and any possible errors or omissions are the responsibility of the consultant and do not necessarily represent those of FONERWA or the sources of information mentioned in the report.

1.2 Government policies on access to drinking water and the role of RWHThe Government aims for 100% of the population to have access to safe drinking water by 2018. The EICV3 of 2011 reports 74.2% (urban 86.4% and rural 72.1%) and only 0.4% coming from rainwater. The baseline survey carried out for the RNRA project4 in 2014 interviewed 1200 users in 6 districts and finds that 28.6% of the population uses RWH as their source of water. But the survey also mentions that over 60% of those use jerricans for storage and these might not have been counted in the EICV surveys (see annex 3 for the selection of EICV3 and the base line survey data).

The water and sanitation policy5 recommends water harvesting as a complementary source of water and mainly in areas that can otherwise only be supplied by pumping at excessive costs (e.g. hilltop locations, lava region). Rainwater harvesting is also included in most District Development Plans to address issues of water and sanitation, environmental protection and disaster prevention. For instance the District of Kicukiro has a target to equip 100% of new buildings and 80% of existing buildings with RWH facilities by 2018, while Rubavu intends to have 46,125 RWH systems installed by 2018 from 290 in 2012.

A feasibility study of rainwater collection systems on public buildings in Kigali City and other towns in Rwanda was carried out in 2010. The study identified 17 high rise, 380 large

1 MININFRA, Feasibility Study of Rainwater Collection Systems on Public buildings in Kigali and other towns in Rwanda 20102 RNRA project document 3 www.wateraid.org/technologies4 RNRA RWH Baseline draft Report Presentation 11 November 20145 Rwanda National Policy & Strategy for Water Supply and Sanitation Services. Feb 2010

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and 380 small public buildings which needed rain water collection systems. The study estimated that it will require an investment of Rwf 28 billion (US$ 40 m) to equip all identified public buildings with rain water storage systems.

1.3 Definition of water harvesting According to Rainwater Harvesting Handbook by African Development Bank (2008) water harvesting in its broadest sense can be defined as the "collection of runoff for its productive use". Runoff may be collected from roofs and ground surfaces as well as from natural catchments for storage in the soil or for groundwater recharge and used for domestic, agricultural, livestock and other purposes. This technical note focusses on rain water harvesting for domestic use for households, schools, hospitals and other institutions. The collected rain water may also be used for kitchen gardens to supplement family food and income.

In Rwanda there is are other rainwater harvesting activities that contribute to climate resilience such as different forms of terracing and collecting run off from slopes for irrigation. These are very important and valuable technologies but are not further considered in this note.

1.4 Benefits of rainwater harvestingCollection of rainwater is of particular interest in areas where there are no suitable surface water sources and where ground water is too deep or too costly to reach (as is the case in most of the hilly areas of Rwanda). Rainwater harvesting is a relatively simple technology using mostly locally available building materials and skilled artisans. Rainwater has the added advantage to be relatively clean in contrast to ground and surface water which are exposed to many more man made pollutants including from fertilisers, pesticides or human waste. WaterAid in its technical brief lists the following pros and cons of rain water harvesting

Table 1: Advantages and disadvantages of roof rain water harvesting

Advantages Disadvantages Relatively cheap materials can be used for

construction of containers and collecting surfaces

Construction methods are relatively straightforward

Low maintenance costs and requirements Collected rainwater can be consumed

without treatment, if a clean collecting surface has been used

Provides a supply of safe water close to homes, schools or clinics, encourages increased consumption, reduces the time women and children spend collecting water, reduces back strain or injuries from carrying heavy water containers

Supplies can be contaminated by bird/animal droppings on catchment surfaces and guttering structures unless they are cleaned/flushed before use

Poorly constructed water jars/containers can suffer from algal growth and invasion by insects, lizards and rodents. They can act as a breeding ground for disease vectors if they are not properly maintained

Benefits of RWH in Rwanda include:

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i. Reduction of time required for collecting water . The Rwanda Water Supply and Sanitation policy 2010 states that on average households –women and children- spend 29 minutes per day on fetching water in rural areas and 9 minutes in urban areas. Water sources were reported within ½ km from the homestead by 54% of the respondents and by 21% within 1 km. About 3% claimed to have to walk more than 3 km. In the case of domestic RWH these time requirements are reduced to practically zero.

ii. Reduction in costs as RWH replaces the costs of buying water from WASAC or other sources. The RNRA baseline survey found an average costs of Rwf 45 per jerrican and a total expenses of Rwf 2,920 per month (which would mean 65 jerricans per month or just over 2 jerricans per day). In the case of families using RWH the baseline found an average savings of Rwf 1,200/month.

iii. Health benefits of additional water supply as it may influence hygiene.

iv. Opportunities for household gardening, livestock care etc if additional water is available

Erosion control is often mentioned as one of the positive impacts of RWH. Capturing of the roof water results in less runoff water and reduces soil erosion on the steep slopes found in many places in Rwanda. However, it is not clear how big this impact of the RWH and how this can be measured.

The RNRA project document6 claims to reduce surface runoff and therefore erosion. The six targeted districts have a total surface of 3,300 km2 and an annual rainfall of around 3,000 million m3 or per month an average of 275 million m3. The project proposes to install a total storage volume of 65,250 m3 which is less than 1% of the average monthly rainfall. Therefore the impact on erosion will be difficult to measure. Investments in specific erosion control measures may be more cost efficient.

The impact of RWH on the utility company (WASAC) is not immediately clear. WASAC will lose revenue as RWH spreads and people buy less water from its system. There will result in a reduction in operating costs, especially less electricity consumption for the pumping stations. However, WASAC still needs to ensure water supply to the population during the dry season when domestic rain water tanks run dry. The utility company will therefore have to invest in the expensive infrastructure while losing some of its revenue.

2 Volume of RWH storage reservoirs2.1 Determination of size of storage reservoirRoof-top RWH systems have basically four elements which are: 1) the roof of the building and in most cases in Rwanda this is made out of iron sheets 2) a conveyance system consisting of pipes and gutters, 3) the storage reservoir (masonry reservoir, plastic tank, jerricans etc) and 4) a delivery system consisting of a tap in the most simple applications or piping and pumps in larger dwellings.

6 RNRA: Rooftop Rainwater Harvesting in high density areas of Nyarugenge, Gasabo, Kicukiro, Musanze, Nyabihu and Rubavu Districts (RWH) Fonerwa project document

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From these four elements, the storage tank is the most costly part of the whole rain water system. Therefore it is important to select the size of reservoir that fits the requirements and financial capacity of the user. If the reservoir is too small, the user will have to face periods where he/she has to buy or collect water from other sources. A larger reservoir will increase the investments costs.

The MININFRA feasibility study7 provides a methodology to estimate the optimal size of the water reservoir for large public buildings which includes factors such as:

1) Rainfall patterns; averages and variations of the seasons and between years2) Catchment area in terms of size (m2) and type of roof: flat versus slope, iron sheets,

tiles or grass cover. For the common sheet covered roofs it is estimated that 85% of the rainwater falling on the roof is actually available.

3) Use of filters which result into some losses4) Daily demand for water for sanitary uses, washing, cleaning, animals and possible

homestead irrigation. Collected rainwater may also be used for drinking provided it is treated.

5) Number of days that are acceptable to the user to be without water. This is an important factor and also depends on what reliable alternatives there are available close to the users such as WASAC piped water, wells, springs etc.

The RainCycle software brings all these factors together and calculates an optimal capacity of the reservoir. The report recommends to choose the smallest tank size that can meet an acceptable amount of the water demand. Any commercial/industrial RWH system that can supply 70-100% of the required volume is generally considered to provide a good level of service.

Large water reservoirs (build above or underground) can in principle be constructed in sizes of up to 30 m3. If more capacity is needed, additional tanks can be constructed. The plastic water tanks that have become popular over the last 10 years are a scalable system whereby tanks can be easily replaced or added at a later stage at relatively low extra costs.

2.2 Rainfall patterns Rwanda has a bi-modal rainfall pattern with the short dry season from December to January and the long dry season from June to mid-September. The average annual rainfall is 1200 mm per year but varies considerably between the drier eastern areas (700 - 1400 mm) and the higher altitude areas (1300 – 2400 mm).

The report “Rwanda’s Climate: Observations and projections, July 2011” provides a detailed overview of rainfall patterns in the country8. Further information on local rainfall patterns maybe be available from the Rwanda Meteorology Agency9.

7 MININFRA, Feasibility study of Rainwater Collection Systems on Public Buildings in Kigali City and other Towns in Rwanda, July 20108 http://www.smithschool.ox.ac.uk/library/reports/Rwanda-Baseline-Final.pdf 9 http://www.meteorwanda.gov.rw/

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2.3 Daily Water demandThe AfDB water harvesting handbook10 estimates daily household demand at 25-40 litres/person/day as shown in the table below.

Table 2: Daily water demand

Purpose Litres/person/dayDrinking only 3 - 5Cooking 4 - 5Washing dishes 3 – 5Personal hygiene 5 - 10Washing clothes 10 - 15Total 25 - 40Source: AfDB Water harvesting handbook

The handbook recommends a storage capacity of between 4 – 5 m3 for a household of five persons which will last for about one month.

These estimates above are only a guidance and need to be adjusted according to local conditions and the preferences of the users. For instance the estimates do notdon’t include the requirement for animals and many Rwandan families keep dairy cows at their homesteads which require about 20 litres/day per animal. There is also the increasing need for supplementary irrigation for homestead gardens, which are promoted by the Government as a means to improve nutrition and family income.

2.4 Some findings of the RNRA baseline survey The baseline study for the RNRA rain water harvesting project was carried out in 2014 water in the high density areas in 6 districts in Rwanda (Kigali (3), Musanze, Nyabihu and Rubavu). The study included interviews from about 1200 households and institutions/ businesses. The survey provides some interesting results;

For households1) Public taps are the main source of water for 46% of the households in the survey and

another 7% have taps within their compound. 2) Nearly 30% of the households claim to use RWH as their main source of water11

3) Jerricans are the most popular means of storage used by 63% of the respondents, metal tanks by 6% and plastic ones by 5 % of the families interviewed.

4) Drinking water counts for 8% of water usage, washing for 29% and cooking for 25%.5) The harvested water is insufficient for the majority of people interviewed (about

72%). It lasts one month on average. Once depleted, many people use piped water or springs.

6) Maintenance is not found to be a big problem7) Reduction in time, allocated to water collection was found a major direct benefit

reported by 57% of the population.

10 http://www.rural-water-supply.net/en/resources/details/268 ADB Rainwater harvesting Handbook 2008. See page 28,11 Note: this is very different from the EICV data reporting 0.4% of population having RWH

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8) 20 – 30% claimed to be affected by flooding, excess runoff and erosion9) Major challenges reported included high costs, limited storage capacity and irregular

rainfall.

For institutions and businesses:1) About 62% of the surveyed institutions and businesses (n=608) use RWH and they get

over 50% of their water from RWH against around 25% from WASAC2) The main use of the water was for washing and cleaning (about 70%)3) Plastic and metal tanks account for 61% and 8% respectively. Those made out of

blocks or bricks account for 6%. Jerricans are also very popular with 21%4) About 72% of the institutions and businesses responded that water storage lasted one

month or less. 20% of the interviewed reported 2 -3 months.

Although the survey was conducted over a limited number of users in 6 districts, it does provide a picture of the application of RWH and gives reasons to believe that while the technology is already widely adopted there is scope for further expansion and improvements. For instance most of the users still use jerricans as storage which limits capacity.

3 Costs of RWH technologies3.1 Investments costs for reservoirsThe MININFRA feasibility study of 2010 and the RNRA project document provide information on the costs of RWH systems for public building and domestic houses respectively. The MININFRA report also has some annexes with detailed calculations.

The MININFRA and RNRA documents show a large variation in costs for different types of types of water storage reservoirs as illustrated in the table below. There are some differences between the two sources but these are not large. Actual prices also depend on location, availability of building material and craftsmen.

The reservoirs can be divided into those that are constructed in situ from blocks, stones, cement and reinforcement bars and pre-fabricated tanks from metals and plastic materials. These are manufactured mostly in Kigali in small industries. The water tanks made out of polyethylene (PE) are available in different sizes from a range of suppliers12 and have become increasingly popular over the last years. For these pre-fabricated tanks, a simple foundation is recommended and these costs are extra.

Table 3: Types and units costs of different storage reservoirs

Description Costs range Observations

In si

tu

Ferro cement tanksfrom 10 – 100 m3

150 – 200,000/m3

Risk of cracking but can be repaired easily Known technology. Larger ones will

requires good artisans.Brick/masonry tanksfrom 5 – 30 m3

150,000 /m3 Long life Known technology, used for larger and

smaller tanks Can be repaired easily

12 See for instance Roto www.rotorwandatanks.com

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Artisanal tank withplastic liner 6 m3

20,000/m3 Well established technology in some rural areas

Local artisans can construct them Easy to repair

Pre-

fabr

icat

ed

Metal tanks 1- 10 m3 160,000 / m3 Locally manufacture Corrosion protection needed

Fibre glass tanks 2- 75 m3 220,000/m3 Long lasting Easy to repair Limited number of suppliers

Polyethylene tanks0.5 – 10 m3

130,000 /m3 Widely available in urban areas Light and quick installation Requires foundation or other support

construction Scalable, start with one and expand

Jerricans 20 litres(used ones for Rwf 2500 each)

125,000/m3 Widely available Easy start up with few jerricans and

scaling up over time if funds are available Labour intensive ( filling) Space needed inside house.

Adapted from RNRA Project Document and MININFRA RWH study of Public Buildings

The prices of PE water tanks need further verification against actual market prices. RNRA documents show costs ranging from Rwf 450,000 to 600,000 for 5 m3 model (excluding costs of plumbing etc) which would be Rwf 90 – 120,000/m3. The costs of these PE tanks in Rwanda appear much higher than in Tanzania where a 5m3 plastic tank is sold for the equivalent of Rwf 250,000. This would require further investigation to validate this observation and if correct, establish the reasons for the difference.

3.2 Costs of guttering systemThe other important requirement for a rain water harvesting system is the guttering system to collect the water from the roof and the pipes to bring it to the storage tank. The RNRA project provides some information on the costs. The most common systems use metal or plastic gutters. In some cases people select the cheaper option of cutting and bending iron roofing sheets which works well for shorter distances. No separate costs are given for bends and connectors and it is assumed that these are included in the prices per unit of 1 meter shown below.

Table 4: Indicative Costs of Gutters

Type of material cost Rwf/mMetal gutter 8,500Plastic gutter 6,000Iron sheet (roofing material) 4,500Source: RNRA documents

For a small house of 120 m2 floor space about 30 m length of gutter will be required which would be Rwf 135 to 250,000 for a complete system, using the unit prices above.

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3.3 Other accessoriesOther accessories might be installed depending on the needs and wishes of the users. A water diversion valve can be installed to reduce the contamination of the initial water flows coming from the roofs. Water filters can help remove sand and other dirt before the water flows into the buildings. While many households will bring the water into the house using buckets and jerricans, higher income groups and public building may want to install an electric pump and overhead tanks.

Costs of the required plumbing and electrical materials are not further included in this technical note but can be obtained from specialised contractors and hardware shops.

4 RWH applications4.1 RWH for households

4.1.1 Typical domestic system using plastic water tanks The table below provides a cost indication for a RWH system using plastic water tanks (PE) and gutters. The calculations are made for houses of small and medium sizes of 120 and 300 m2 covered surface respectively.

The costs are estimated at Rwf 0.7 and 1.3 m respectively. Additional investments are needed if the RWH is equipped with water filter, electric pump and piping to conduct the water into the house.

Table 5: Estimated costs for RWH system for small and medium domestic houses

Description Unit Quantity % Quantity %House dimensions m2 8*15 =120 m2 15*20 = 300 m2Reservoir capacity m3 5 10 Costs reservoir/ m3 Rwf/m3 90,000 90,000 Costs of reservoir Rwf 450,000 63% 900,000 70%Length gutter m 30 40 Costs gutter per meter Rwf/m 7,000 7,000 Costs of gutter Rwf 210,000 30% 280,000 22%Accessoiries Rwf 50,000 7% 100,000 8%Estimated total costs Rwf 710,000 100% 1,280,000 100%Source: Own calculations

The RNRA project promotes the use of plastic water tanks (PE) in size of 2 – 5 m3 for domestic houses because of their costs, availability and ease of installation and maintenance. The project provides a 40% subsidy on the costs of the tank to the income groups ranked Ubudehe 3 and 4 and also facilitates access to credit for those who can afford. The households themselves have to arrange for the foundation, the gutters and other accessories to complete the system.

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4.1.2 Domestic systems using low cost storage reservoirRNRA promotes the construction of low cost reservoirs made out of bricks with a plastic liner. The project feasibility study found these artisanal tanks already widely adopted in the Shangasha Sector of Gicumbi District (the report mentions that 90% of the households were using the system).

The "shangasha" technology is a simple design that uses predominantly local materials (bricks, cement, heavy duty plastic as liner, metal sheets and timber for the roofing. The costs for a storage capacity of 6,000 litres vary between 80,000 to 100,000 Rwf or around Rwf 15,000 per m3 water storage capacity. This type of RWH facility is reported to be well adapted to the local conditions. RNRA plans to support 4000 families in the lower household group and will provide them with the plastic liner and roofing sheets for the cover.

Figure 1: Artisanal water reservoir (Shangasha) under construction and completed with roof.

4.1.3 Financial Benefits of RWH

The households covered in the RNRA baseline survey of 2013 reported an average costs of Rwf 45 per jerrican and total expenses of Rwf 2,920 per month. This means about 65 jerricans per month or just over 2 jerricans per day). For families using RWH the baseline found an average savings of Rwf 1,200/month. Assuming that the RWH system will supply 100% of the household’s water requirements, the annual savings would be about Rwf 35,000 (two jerricans/day over 365 days and Rwf 45 per jerrican).

Payback time depends on the capital and operating costs. In case of an investment of Rwf 0.7 m for a typical domestic system the payback time would be about 20 years, and longer if interest rates and operating costs are taken into account. There are clearly other advantages than just the financial benefits which motivate households to install RWH (see section 1.4).

Financial support through subsidies (like provided under the RNRA project) or access to affordable credit maybe be needed to speed up the dissemination of domestic RWH systems. To justify such support, a good understanding is needed of the other additional benefits of RWH including improved health and sanitation, reduced workload for women and children, impacts on education and opportunities for income generation through kitchen gardening.

4.2 RWH for Communal SystemsThe first communal rainwater water system was constructed in 2008 in Rubaya, Gicumbi demonstration project which covered 43 households. More recently a larger system was

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completed in the Muyebe Green Village in Muhanga which collects water from the roofs of 100 individual houses. Pipes conduct the water to the lower end of the village where it runs through a sand/gravel filter before entering in the underground reservoirs which have a total capacity of 1500 m3. That results in 15 m3 storage per household which appears very high. It is reported that the water is also used by some people outside the village but there was no further information on number of beneficiaries.

No detailed costs were available of this RWH system as the construction was carried out under a contract combination with communal biogas digesters. The contractor did mention that the total costs for the water harvesting and biogas systems were Rwf 600 million which would be Rwf 6 million per household.

Under ground water reservoirs Water supply tapsFigure 2: Communal rain water harvesting; Muyebe Green Village, Jan 2014.

The Kimonyi Village in Musanze district has a population of around 1100 persons living in 184 households. A pre-feasibility study13 was carried out in 2013 and the consultant’s report recommended the installation of a communal rainwater collection system bringing together the rain water from 150 roofs and to be stored in large underground water tanks (15 * 100m3 or 1500 m3) at the lower end of the village. This means an average water storage of 10 m3 per connected household but again there may be more beneficiaries from outside the village.

The unit costs for the tanks and conveyance systems were estimated by the consultant’s report at Rwf 220 – 250,000 per m3 which would be Rwf 2,2 to 2.5 million for 10 m3. The RNRA project document provides a price of Rwf 1.2 m for the plastic water tank of 10 m3 (excluding the costs of foundation and plumbing), which is about ½ of the costs reported in the communal system.

Table 6: Pros and cons of communal RWH systems

Pros Cons Solid design with long life expectancy if

maintained properly Includes water filter to reduce

contamination

Investments costs are higher than for individual units

Need for strong management system to ensure maintenance and equitable

13 Consultancy support to the CKDN project funded by Rwanda FONERWA capacity building, Biogas REC, 2013

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Easier to check water quality than for individual systems

Contributes towards community spirit in the village

division of water Water has to be carried back to the house

4.3 RWH for public buildingsThe MININFRA feasibility study of rainwater collection for public buildings in Kigali city and other major towns in Rwanda was carried out in 2010. Buildings were ranked in different categories depending on size. The study identified 17 high rise, 380 large and 380 small public buildings which needed rain water collection systems. The report has three annexes i) an inventory of public buildings, ii) bill of quantities for sample RWH systems and iii) plans for the storage tanks

The study uses a software package (RainCycle) to come to an optimal design of collection/ storage systems that takes into account rainfall data, roof areas, losses, daily demand for water, construction and operating costs and other factors. The study estimated that it would require an investment of Rwf 28 billion (US$ 40m) to equip all identified public buildings with rain water storage systems.

The table below provides an overview of the three categories of public buildings and their main characteristics.

Table 7: RWH for public buildings

Type and main characteristics LayoutHigh rise buildings (17 reported)

Roof area 500 – 1,000 m2 Flat roofs, cemente Underground reservoirs Pump to bring water to header tank on the roof

Estimate average costs; Rwf 50 m

Large buildings (380 reported) Roof area 1,200 to 6,000 m2

Iron sheet roofs Schools, health centres, markets, district offices Large storage; under of above ground Water pumped back to roof tank or direct throuhg

pipe network

Estimates average costs: Rwf 65m

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Small buildings (380 reported) Roof area 100 – 500 m2 Iron sheet roofs Above ground tanks: cement or plastic

Estimated average costs: Rwf 10 m

5 RWH for irrigation purposes SHOULD WE REMOVE? Agriculture is the biggest user of water in Rwanda accounting for up to 70% of the water demand and is expected to increase to 80% in 202014. The GoR wants to increase irrigation to boost agricultural production. Recent studies estimate that Rwanda has a potential of 589,000 hectare of irrigated land. MINAGRI targets to increase irrigated area from 18,000 ha in 2010 to 100,000 ha by 2017. This six-fold growth in irrigated agriculture will result in more pressure on the country’s water resources.

Rain water harvesting for small scale irrigation has been tested and promoted in Rwanda for many years. SEARNET15 describes for instance the work done by the World Agro Forestry Centre (ICRAF) using satellite and GIS based methods to identify best opportunities for rainwater harvesting systems for agricultural purposes. The programme worked closely with local communities as water harvesting is more than a matter of constructing ponds, dams or tanks. It requires involvement of the local communities in setting up and maintaining the system and share the water sustainably and equitably. Earthen ponds of different sizes using with plastic lining have been constructed in several districts collecting rainwater from nearby slopes, roads etc. At a later stage some of the ponds were equipped with a rope and washer pump to support water distribution. The programme worked on 90 farm plots and trained 175 farmers, 30 agriculturalists and trained 17 technicians.

Typical pond for storing run off water Pond with rope and washer pumpFigure 3: Rainwater harvesting for irrigation

Presently, the total number of irrigation ponds in the country is given as 1376 out of which 735 are working, 171 requiring repair, 350 planned/implemented and 120 ponds are under

14 Rwanda Water Resources Management Sub-Sector strategic plan 2011 – 2015, Dec 201115 http://www.searnet.net/index.php?id=62

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construction. These are in 16 relative drier districts of the country. The ponds are of the storage capacity of 120, 250, and 480 m3 irrigating 0.25ha, 0.5ha and 1ha respectively. Assuming an average of 0.5ha, the total area that can be irrigated from these surface ponds is estimated as 688ha (RAB 2012). The investments costs of these plastic lined water reservoirs are given as Rwf 1 m for 120 m3, Rwf 1.5 m for 250m3 and Rwf 2,2 m for 480 m3.

More details on the use of ponds and small dams are available from MINAGRI and in particular from the Irrigation and Mechanisation Taskforce. The Rwandan Agricultural Board provides expertise in rain water harvesting. Their website16 mentions that the nature of land in most parts of Rwanda offers an opportunity where different rain water harvesting technologies can be implemented such as runoff ponds system with different capacities of 120 – 480 m3 and below and above ground tanks with capacities of 25m3, The website also points out other water harvesting technologies such as trenching systems, relay systems and planting pits which increase infiltration of water in the ground. RAB provides expertise and guidance in different terracing technologies which are another form of rain water retention in the ground to increase availability of water to the crops and reduce soil erosion.

16 http://www.rab.gov.rw/spip.php?article10.

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Annex 1; List of publications on RWH

Documents with detailed technical information and costs indications in Rwanda1. RNRA: Rooftop Rainwater Harvesting in high density areas of Nyarugenge, Gasabo,

Kicukiro, Musanze, Nyabihu and Rubavu Districts (RWH), Project Proposal to FONERWA 2013

2. RNRA RWH Baseline draft Report Presentation 11 November 20143. RNRA Baseline Study on Rain Water harvesting in High Density Areas in Kigali City,

Musanze, Nyabihu and Rubavu Districts (RWH project) draft report Oct 2014.4. RNRA Newsletter shangasha water reservoirs, Sept 20135. MININFRA, Feasibility study of Rainwater Collection Systems on Public Buildings in

Kigali City and other Towns in Rwanda, July 2010. Annexes 2 and 3 provide Bill of Quantities and designs of the RWH systems

6. Biogas REC; Consultancy support to the CKDN project funded by Rwanda FONERWA capacity building, 2013. Information on Communal RWH systems

Government Policy Documents7. Rwanda Water Resources Management Sub-Sector strategic plan 2011 – 2015, Dec

20118. Rwanda National Policy & Strategy for Water Supply and Sanitation Services. Feb

20109. RWH Strategy and management plan, MINIRENA, June 201410. Ministry of Natural Resources; Rain Water Harvesting and Management Strategy

2012/13 – 2017/1811. Rwanda’s Climate: Observations and Projections Appendix E, Smith School of

Entreprise and Environment SSEE, July 2011. Information on rain fall patterns

Global RWH documents12. ADB Rainwater harvesting Handbook 2008.13. SmartWater Harvesting Solutions, Netherlands Water Partnership NWP, 200714. Rainwater Harvesting; Technical Brief, WaterAid, Jan 2013.

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Annex 2: Costs tables of RWH systems

Table 2.1 Indicative costs of RWH tanks; RNRA project reports

Costs of rain water harvesting tanks

Description Volume m3

Construction costs Rwf

Plumbing Rwf

Total Rwf

Unit cost Rwf/m3

60 7,735,040 175,000 7,910,040 131,834 45 6,921,670 168,000 7,089,670 157,548 30 5,742,860 168,000 5,910,860 197,029

Underground tank , spherical 100 6,783,820 411,480 7,195,300 71,953 10 1,200,000 50,920 1,250,920 125,092 5 600,000 50,920 650,920 130,184

Artisanal tank lined with plastic 9 102,565 15,000 117,565 19,594

Ferro-cement , reinforcment, chicken wire and cement layers

Plastic tank, polyethylene (black tanks)

Source: RNRA rain water harvesting project.

Table 2.2: Indicative costs of RWH tanks and materials (source; RWH harvesting for public buildings)

Type of material Common Sizes Costs

Rwf/m3Comments

Metal 1 - 10 m3 160,000 Corrosion possible Fibreglass tank 2 - 75 m3 220,000 Can last for decades, easy to repairPolyethylene plastic (mostly black)

1- 20 m3 130,000 Easy to transport, light

Brick/masonry tanks 5 - 30 m3 150,000 Mixed reinforced concrete/ stone/ masonry

10 - 100 m3 200,000

Reinforced concrete usually up to 30 m3 350,000 risk of cracking but easy to repair, smell and taste of water can be affected. Tank can be fitted with plastic lines

Costs of gutterstype of material cost Rwf/mMetal 8,500Plastic 6,000Iron sheet 4,500

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Annex 3: Access to water; EICV3 and RNRA baseline data

Table 3.1: Proportion of households with improved drinking water source, by province and urban/rural (source: RWH Strategy and management plan June 2013)

EICV3 Total: improved drinking water source

Improved water source No of HHs (in 000s)Protected

springPublic standpipe

Piped into dwelling/ yard

Bore hole

Protected well

Rain water

Surface water (river or lake)

Unprotected spring

Unprotected well

Others

All Rwanda 74.2 38.1 25.7 5.8 1.8 2.3 0.4 11.6 10.6 2.3 1.3 2253Kigali 82.7 10.0 35.0 32.6 2.1 3.0 0.1 4.4 3.7 0.9 8.3 223Southern 74.8 54.6 13.2 2.1 0.1 4.7 0 11.1 11.0 3.0 0.1 549Western 74.2 41.0 25.7 3.6 1.1 1.7 1.1 5.8 18.2 1.4 0.5 528Northern 78.9 46.6 26.6 4.1 0.1 1.0 0.5 9.7 10.2 1.0 0.2 411Eastern 66.6 23.9 33.9 2.1 5.4 1.2 0.1 22.3 5.8 4.0 1.4 542

Urban/rural Urban 86.4 21.4 33.0 27.8 1.5 2.4 2.0 4.8 2.1 0.9 5.8 331Rural 72.1 41.0 24.4 2.1 1.9 2.3 0.4 12.8 12.0 2.5 0.6 1922

Source: Reduced after EICV3 2011: The Third Integrated Household Living Conditions Survey (EICV3); Main Indicators Report; National Institute of Statistics of Rwanda; 2011.

Table 3. 2: Sources of water (RNRA Baseline survey in 6 districts, 2014)Source ShareOwn tap 7.0%Communal tap 42.5%RWH 28.6%Commual RWH 0.9%Hand pump 3.1%Rivers 4.4%Dug well, protected 2.2%Dug well, unprotected 7.0%Off rain water (?) 0.4%Others 3.9%

100.0%