MatmaI Resaurcss Seria - No. 4

SRI LANKA

Yaiitha Nanchanayake and

C.M- Madduma Bmdasa

Water Resources

of

Sri Lanka

Water Resources

Sri Lanka

Palitha Manchanayake

and

C.M. Madduma Bandara

National Science Foundation 4715, Maitland Place

Colon1bo 7 SRI LANKA

First published 1999

0 National Science Foundation 47/5, Maitland Place, Colombo 7, Sri Lanka (1999)

All Rights Reserved

No part of lhis publication may be produced, stored in rctrieval system, 01- transmitted in any form or by any means, dlectronic., nlechanic~~l, photocopying, recording or otherwise without the prior permission of' ihe publisher.

ISSN : 1391-2488 ISBN : 955-590-008-6

Printed by

National Science Foundation 47/5, Maitland Place

Colombo 7 Sri Lanka

Tel: 94-1696771-3 Fax: 94- 1-691691 e-mail: info@nsf.ac.lk

FOREWORD

The Committee on Natural Resources of the National Science Foundation (NSF), formerly Natural Resources, Energy and Science Authority (NARESA) under took sometime ago to publish a series of contributions from distinguished scholars on diverse topics in the field of the Natural Resources. This monograph on Water Resources of Sri Lanka is the latest in this series and is authored by Mr Palith Manchanayake and Prof. C.M. Madduma Bandara.

The authors take the reader through Sri Lanka's ancient hydraulic civilization which was based on reservoir systems. They refer to the control devices leading to sophisticated water and sanitation system that reflected the ingenuity of the ancient Sri Lanka Engineers. This monograph illustrates how water resources could be harnessed in the development of the economy and the quality of life.

The authors describe in detail the available water resources in the country, and how these could be developed in the modern context. Among the many aspects discussed are the deterioration of water quality due to the impact of agricultural, industrial and domestic uses. Efficient control of use of water for consumption and recycling methods are also discussed.

The NSF is glad to be associated with the publication of this important monograph under the authorship of Mr Palitha Manchanyake and Prof. C. M. Madduma Bandara. The asistance rendered by Mr M. Watson, Director Scientific Affairs and Miss Anusha Amarasinghe, Assistant Director-Scientific Affairs of the NSF is also acknowledged.

I trust that this publication would serve as a valuable reference guide towards efficient utiliazation of S1-i Lankan Water Resources and eventual development of a National Water Policy.

Prof. Kapila Dahanayake Chairman National Science Foundation

PREFACE

The National Science Foundation (former Natural Resources, Energy and Sci- ence Authority of Sri Lanka, NARESA) is producing a series of publications of themes such as geology, climate, energy, soils, land and water. These publications are expected to incorporate available basic information pertaining to each theme, and this monograph on "Water Resource of Sri Lanka" has been written at the request of NARESA to cover the theme of water resources.

The monograph provides a broad outline of the water resources of' Sri Lanka, covering their different aspects, usage and potential fbr development. It is not a complete reference work on this subject; nevertheless, an attempt has been made to give a general coverage of the most important aspects.

Furthermore, a n endeavour has been made to invorporate the more recent development on the different topics that are dealt with. However, it may be noted that, many significant changes have taken place in the field of' water resouces management during the last few years and some changes are still being made. Therefore, some information may not be completely up-to-date. A few figures, tables and maps have been included in order to illustrate certain aspects oi'the text. A text of this nature has been a long-felt need, and this is an attempt to fill the existing void.

The authors wish to express their appreciation to Mr D.G.L. Ranatunga, former Director, Mahaweli Engineering and Construction Agency, and former Divisional Irrigation Engineer (Hydrology), Irrigation Department , for making many valuable suggestions to improve the manuscript. Subsequent editorial contributions of' Prof. P.G. Cooray (Visiting Professor, University of Peradeniya), are also gratefully acknowledged.

They also wish to aclrnowledge the help received fi-om Shyamali Siriwardane, Saroja de Silva, Ramani Mudalige, Sumedha Amaratunga, Prasad Perera, Saman de Silva and Upali Herath ofthe Water Management Secretariat, Mahaweli Authority of Sri Lanka, in the preparation of tables and drawings and in word processing of the script. The authors are also thankful to Mr Ranjith W. Pathiraja, Data Processing Manager, Computer Centre, Water Management Secretariat, for the valuable assistance given, and to Mr C. Chandrananda, Mr K.G. Gunaratne and Mr G. Dharmadasa for word processing the revised version.

Pal i tha Manchanayake C.M. Madduma Balldara

November 1998

FOREWORD

PREFACE

CONTENTS

FIGURES

TABLES

i x

C O N T E N T S

CHAPTER 1 General Background 1.1 HISTORICAL SKETCH

1.2 GEOGRAPHICAL S m 1 N G

1.3 GEOLOGICAL BASE

1.4 LAND RESOURCES AND THEIR UTILIZATION

1.5 ACRICUL"I'UR1.:

1 .ti POPUI-A'I'ION AND TRENDS

1.7 EMP1,OY MEN'I' I'fiITERN

1 .X INIIUSTRY

1.9 TIUNSPORT AND COMMUNICA'IION

CHAPTER 2 Water Resource Availability 2.1 HYDROLOGICAL INFORMATION

2.2 HYDRIKICUCAL C M S H PROGRAMME

2.3 tXAINFAL,L: THE SOUIiCE Or; WATER

2.4 SURFACE WA'I'EII RESOURCES

- 2.5 GIIOUND \4fATER RESOURCES - 2.6 EVAPO-~~lMNSPIIIAAI'ION

P

CHAPTER 3 Water Resources Developmefit 3.1 MAHAWELI PROJECT REGION

3.2 SOU'TFI-EAST DRY ZONE REGION

3.3 WESTERN WET ZONE REGION

3.4 NORTI I-WEST DIZY ZONE REGION

uii

3.5 ECONOMIC ASPECTS 012 WATER RESOURCES DEVELOPMEN'I'

3.6 SUPPLY AND DEMAND FOR WATER

3.7 WATER RESOURCES SYSTEMS

3.8 ECONOMIC FEASIBILITY

3.9 MULTI-OBJECTIVE PLANNING APPROACH

CHAPTEI? 4 Utilization of Water Resources

4 . 1 PUULIC W/\T13R SUPI'LY

4.2 INIlUSriIIAL WA'I'GR SUI'IJLdY AND DISPOSAL 01" EFFLUENTS

4.3 USE OF WATER FOR IRRIGA'I'ION

4.4 CLASSIFICATION OF IRRIGATION WORKS

4.5 EFFICIENCY O F WATER USE IN IRRIGATION

4.6 PROBLEMS ASSOCIATED WITH IRRIGATED AGRlCULTURE

4.7 CROP WATER REQUIREMENTS

4 .8 HYDROPOWER

4.9 PRESENI' POWER VACILITIES AND POTENTIAL HYDRO POWER RESOURCES

4 10 USE OF WINL) ECNEIICY FOR LIFI'ING M'ATEIi

4.11 SEWAGL AND LVASTE L)ISIJOSAL

4.12 WATER USE FOR OTl-IEK PURPOSES

CHAPTR 5 Water Laws and State Policy 87

5.1 STATE POLICIES

5.2 \VKI'EI< I,k\LVS

5.3 LEGISLATION IN SRI LANIIA

5.4 OWNEI<SI I l l ' 01: \VA1lLCli

5.5 \VA-I-ICII I<IC t r r s

5.6 SECTOIAL LEGISLATION

5.7 WATER WASTE, QUALITY AND POLLUTION CONTROL

CHAPTER G Water Resources Management Institutions

6.1 EVOLUTION OF WATER-MANAGEMENT INSTITUTIONS

CkIAPTER 7 Towards a National Water Policy

S l : l ~ ~ c ~ , s i3li~l~loc~l~,\~liY

xi

FIGURES

Figure 1.1 Distribution of Dry Zone Tanks (in use and abandoned) 2

Rgtlre 1.2 River Basins of Sri Lanka 7

Figure 1.3 Relief Map 9

Figure 1.4 Main Geological Formatic~ns 11

Figure 1.5 Volume of Lifetime Migration from District of Birth to District

of Enumeration of Morc than 10,000 Migrants (1981) 16

Figure 2.1 Mean Annual Rainfall and Discharge of Main Rivers 26

Figure 2.2 The Trend of Annual Rainfall a t Nuwara Eliya (1870-1980) 31

Figure 2.3 Quality ofwater in Tube Wells 39

Figure 3.1 Water Resources Development in Sri Lanka 44

Figure 3.2 Mahaweli Water Reso~~rces Management Project - Ir

r

igation Systelns - Systerns H,IH and MH 47

Figure 3.3 Mal~aweli Water Resoul-ces Management Project - Macro

System-Mahaweli Ganga 48

Figure 3.4 Mahaweli Water Resources Management Project - Irrigation Systems-

Systems E, B and C 50

Figure 3.5 Mahaweli Water Resources Management Project - Irrigation Systems-

Systellls G, Dl and D2 5 2

Figure 3.6 Mahaweli Water 1Zesources Management Project - Macro

System-Kelani Ganga

Figure 4.1 Sri Lanka Domestic Water

xii

TABLES

Table 1.1

Table 1.2

Table 1.3

Table 1.4

Table 2.1

Table 2.2

Table 2.3

Table 2.4

Table 2.5

Table 3.1 '

Table 4.1

Table 4.2

Table 4.3

Table 4.4

Ownership of Land

Population (in thousands)

Labour Force Projection for Sri Lanka (in thousands)

Erl~ployed Population Classified by Industry (Major Divisions)

and Sex (1982)

River Basins in Sri Lanka (Ref. fig. 1.2)

Water Resources Availability in Sri Lanka

Surface Water Resources (average upto 1972)

Water Quality of Limestone Aquifers

List or Pan-Evaporation Station, Sri Lanka

Major Components of the Accelerated Mahaweli 1'1-oject and

Their Dates of Completion

Estimates of Reference Crop Evapo-transpiration for Various

Regions of Sri Lanka

Crop Coefficients for Crops a t Different Stages of Growth

Power Generation Px-ojects in Sri Lanka

Salient Features of the Existing and Future Hydro Electric

Development Projects

General Background

The dependence of Sri'Lanka's economy and society on her water - -. resources remained remarkably highin the historic past andis likely to continue

to be so in the present as well as in the future. The highest national investment today is on development prqjects related to water resources such as tllosc fbr

-C i

r

rigation, hydro-power generation, and rural and urban water supplies. Thus the Mahawcli Project alonc, the construction work on which was started 111 1970, accounted for ovcr 50 billion I-upces by the end ofthe 1980s. The coilser\lutloll and efficient managerncut of' water resources in Sri Lanka is tlier.efbre a vital need for the progress of the nation.

1.1 HISTORICAL SKETCH

Historically, one of the fields in which Sri Lankans have displayed rare skills in managing nature and its riches is undoubtedly in the development of water resources. The map of Sri Lanka, particularly its Dry Zone, is dotted with literally thousands of ancient tanks of varying sizes and shapes (Fig.l.l), some operational and othe1.s still abandoned. It was around these ancicnt tank systems, that the econonly and human settlements of early Sri Lanlca grew a]-ld flourished. The historiails characterize this early Sri Lankan socicty as a 'hydraulic civilization' (Leach,1957; Needham 1971). Unlike in the case of most ancient civilizations which grew in fertile river valleys and flood water retention areas, Sri Lankan hydraulic societies were based on reservoir systems and control devices or biso-kotuwas for the release of irrigation vt.ater. I t has been reported that at the zenith ofits development, the ancient Sri Lankan hyd

r

aulic engineers were even called upon to serve in other countries. Similarly, the urban water and sanitation systems, as seen at Anuradhapura and Sigiriya with their ponds and fouiztains, bear ample testimony to the ingenuity of ancient Sri Lankans in the field of water resources.

It has been recorded that Sri Lanka was practising irrigation as far back a s 500 B.C. The practice of irrigation in our country thus has a tradition of over two millennia, and our ancient civilization has been described as one ofthe oldest in the world, The annals of our history are replete with evidence of how our ancient kings built massive irrigation works or improvedupon those constructed by their predecessors. No king of ancient Lanka was deemed a benefactor of his people had he not delivered the people fi-om foreign domination, or caused the construction of some irrigation works. Indeed, our ancient kings showed a remarkable preoccupation with irrigation, for which people have deified them.

PALITHA MANCHANAYAKE & C.M. MADDUMA BANDARA

tanks per nap shrt.

1

0 mo hm

Scale

Figure 1.1: Distribution of dry zone tanks (in use and abandoned).

WATER RESOURCES OF SRI LAN= 3

Perhaps the early settlers in Lanka who preceded the Aryans, too, may have had some knowledge of' tank construction. The Mahavansa records that Prince Vijaya, on setting out with his men into the interior of Lanka, met Kuveni by a pond or lake where the prince was invited to drink and bathe. Brohier (1935), refcrringto the advent of'vijaya and his fbllowersin the 5th century B.C., maintains that " ... Sinhalese invaders of the 5th Century B.C. foi~i~d zrrigation works fornzed by the aborigines wlzo preceded them ..." More recently, the late H.de S. Manamperi (1968) argued that whether the lake referred to in connection with the landing of Vijaya was meant for irrigation or for domestic purposes is not clear. However, he states that from the consideration of rainfall in the area itself, the storage of water must have been essential for the life of the people in this region.

From the elementary knowledge of irrigation engineering that they brought into this country, the early Aryans, who came to be known as the Sinhalese, developed an intricate engineering science, the application of which led to the progressive building of'a colossal and complex system of inter-related dams, networks of canals and tanks, the like of which has not been found anywhere else in the contemporary world of that time.

Indeed, for 15 centuries from 450 B.C., the "Rajarata", with capital cities a t Anuradhapura and Polonnaruwa, sustained a remarkable agricultural prosperity and the kings who ruled from there left behind evidence of a glorious civilizatioll whose achievements have held the historian and scholar spell- bound.

The monastic architecture of our ancient kings, their sculpture, and the stupendous irrigation worlis reflect the refinement of their art and the engineering ingenuity of that civilization. The massive dagabas, royal baths, image-houses and statues all show a refinement unmatched later and unsurpassed since. At the zenith of the Polonnaruwa regime, the material prosperity of the people resulted in Sri Lanka exporting rice, and the country came to be known as the "Granary of the East".

Furthermore, the early Aryan settlers in Sri Lanka, who came from North Eastern and North Western India, possessed a knowledge of irrigation and rice cultivation. These settlers, who presumably made their way into the interior of the country along the banks ofrivers, pitched their homesteads on the flat, dry-zone plains, which were ideal fbr rice cultivation. Finding that these areas were subject to droughts with rain uncertain,-the Aryans devoted their energies to the storage of water in reservoirs by the collection of rain water or by the diversion of streams and rivers into these reservoirs (Irrigation Department, 1975).

4 PALITHA MANCHANAYAKE & C. M. MADDUMA RANDARA

The kings who ranked highest among the monarchs for their engineer- ing skills wereMahasena (274-301 AD) andKing Parakrama Bahu l(1153-1186 AD). King Mahasena had a large number of reservoirs to his credit, including Minneriya and Padaviya. The people ofthe locality refer to him even today with honorific titles such as "Hathrajjuru Bandara-Minneri Deviyo" or "Mahasena Deviyo" as a mark of respect for the services he had rendered in the field of irrigation. Special mention should be made of Minneriya Reservoir, built by Mahasena, which not only serves the nation today, but has been unique in that it has never been breached throughout the centuries of its existence. f i n g Parakrama Bahu I also had a large number of reservoirs to his credit, including the massive Parakrama Samudra, which serves the nation even today. Efing Dhatusena built the Kalawewa Reservoir around 473 AD and also constructed the 88 km long Jaya Ganga, a canal from Kalawewa to Tisawewa in Anuradhapura. This canal has been constructed with an amazingly small gradient of around 0.20 m k m in its first 11.17 km. With primitive equipment and the technology that prevailed in those days, finishing a job with such precision and accuracy, is a question that baffles most civil engineers, to this day.

The famous dictum of King Parakrama Bahu I, the epic hero of the Poloilnaruwa Period, states that "Let rzot even orze dl-op of'wutcr thut fulls or1 t l ~ c earth i n tlze fornz ofrain beallowed to reaclz tlze sea withorrt being first rnacle r~.sefii/ to man". This denotes a lofty ideal and no doubt reflects ail cnlightencd knowledge of' Irrigation policy and engineering.

No large engineering works appear to have been constructed after the decline of the Polonnaruwa period in the 12th century AD, and most of' the irrigation works were left to ruin in the course of time.

The reasons that led to the collapse of the ancient civilization is an academic maze where many imaginations have wandered. The climatic change, malaria, impoverishment of soil, foreign iilvasions and famine, are o~ily some of the reasons attributed to this historical catastrophe. Paranavitane, the veteran archaeologist and historian of Sri Lanka, believed that the breakdown of' thc efficient irrigation management system was a result of the debilitation 01.

annihilation of the kulinas (the nobility who possessed the irrigation expertise) by the invading forces - the immediate cause for the collapse ofthe hydraulic civilization. While some scholars attributed this to a combination of factors, others attempted to explain it in terms of a push-pull mechanism in which the wet zone began to pull the population from the dry zone where many factors conspired to push them. As Toynbee -the great historian pointed out, at various times and places the recalcitrant Nature, once broken in by human heroism has broken loose again because later generations have ceased for some reason to keep up the constant exertions required of them in order to maintail1 the mastery which had been won for them by their pioneers.

WATER RESOURCES OF SIU LNVI(A 5

There is apparently no record of any serious attempts to restore the irrigation worlis duringthe period of Portuguese occupationfi-om 1505 to arou11d 1640. The D~ltcl?, who occupied the country later, from around 1640 upto 1795, restored a few ofthe irrigation works, mainly in the maritime areas, to encourage paddy cultivation. But their efforts were mostly directed towards the develop- ment of water courses for navigation, to improve trade and commerce in the coastal zone ofthe country. Some ofthese early Dutch canals still exist, and some of them are still in use.

During the early pel-iocl of British rule, the Colonial Government was preoccupied wit11 military and political consolidation, and thcrealtei- in tho dcvclopment of'plantations. Thus, in the period 1815 to 1857, the maintcnance of' irrigation works was totally neglected. During the Uva Rebellion in 1818, the British ~~iethodically deniolishcd the mainstay of the people's economy, by destroying the existing irrigation networks. They destroyed some ofthe tank builds, sluices and spillways. Above all, the abolition of majalzuriya - - the traditional system of common property management - - in 1832, had a devastat- ing negative effect on the maintenance of irrigation canals and reservoirs.

If any British Governor deserves special mention for his contribution to water resources development, i t should be Sir Henry Ward (1855-69) fbr his enliglltenect i~.rigation policy. Sir Henry Ward felt that the Colonial Gove~*nmcn t bcfore him had "tzeuer deuoted a fc~il- propot-ti or^ of the I . ~ ' U C I L L L ~ ~OLULLI-ds the 1-estot-atio7~ of'the o/d WOI-ksn and that " t l~e one tlzilzg tlzat conres to cue]-y Si~rhcilc,se is t l ~ e ~1rt.pt.ot1ei~~ei~t of those nzearzs of irrigatior~ whiclz tlre C / I I ~ L ( L ~ C ~ , e t ~ d e r e ~ / ~f~dzspettscrblc~". Thus, he errharked on a programme ofwork which was p i~ i~sue~ l later with cqual vigour by Sir William Gregory (1872-77).

The irrigation schemes were first undertaken by the Irrigation Sectioii of the Public Works Department (P.W.D), which came into existence around 1860. Subsequently the Irrigation Section branched out from the P.W.D. and became the Irrigation Department, with its own identity, on 15tb May 1900. Mr.H.D.S. Ward was the first Director of Irrigation and Mr. Henry Parlrer (the celebrated author of "Atrcie~zt Ceylonn) came a s his Deputy. Tlle Irrigation Department came under the Mi~istl-y ofAgriculture and Lands in 1932. Until 1930, the Department bras almost exclusively engaged in the r'epalr, maintc- nance and opel-ation of'ancicnt irrigation schemes. About 100 main irrigation schemes were completed during this period and nearly 65000 h a of paddy lalids had come under these schemes by 1930. Other than the mainirrigation schemes, the Department had also repaired many small, or minor irrigation works, village tanks and diversion weirs.

6 PALITHA MANCHANAYAKE & C.M. MADDUMA BANDARA

With the Donoughmore Constitution of 1930, a new agricultural policy came into effect under the able leadership of Hon, D.S. Senanayake, the first Minister ofAgriculture and Lands, and subsequently the first Prime Minister of Sri Lanka. In this new policy, irrigation was the predominant element, and its objectives were two-fold, namely, to increase the paddy production ofthe country and to enable more people to settle on the lands in the Dry Zone. Its purpose was to reduce unemployment and lessen the pressure of population in the Wet Zone of the country. During this period, he started a number of colonization schemes, by restoring ancient irrigation works, such as Minneriya, Minipe, Elahera, Kalawewa, Allai-Kantale, Parakrama Samudra and Padawiya. The construc- tion of the massive Senanayake Samudra of 950 million mJ capacity, irrigating 48000 ha in the Gal-Oya valley and its settlements, remains a lasting tribute to the irrigation works that H0n.D.S. Senanayake so fervently promoted.

A large number of irrigation schemes were developed after the 1950's, including Udawalawe. Rajangane, Kaudulla, Muruthawela, Pimburettawa, Nagadeepa, Mahawewa, Wahalkada Wewa, Inginimitiya, Muth~~knndiya Wewa and Lunugamwehera.

1.2 GEOGRAPHICAL SE'lVl'lNG

Sri Lanka is an island located in the Indian Ocean to the east of the southern tip of India, from which it is separated by the Palk Strait. The Island lies between the latitudes 5" 55'N and 55' N; and longitudes 79" 42' E and 81" 52' E. I t is 440 km long from north to south, 226 km wide a t the broadest part, and has a total land mass of 65621 km2.

Sri Lanka has 103 distinct river basins, most of'thc rivers have t l~c i~ . origin in the central highlands and flow down to the sea (Fig.l.2). The longcsl river is the Mahaweli Ganga, 355 km in length, which drains an al.ea of' 10448 kn12, which is nearly one-sixth the entire area of the Island. The other long rivers are the Malwatu Oya, the Kala Oya, the Kclani Ganga, theyan Oya, the Ileduru Oya and the Walawe Ganga, all of which are of lengths varying between 140 Irm and 160 km.

The rivers of Sri Lanka, although short, have complex long profiles. They are steep in their upper reaches, but flatten prematurely in their middle and lower reaches, forming flood plains. Despite their size, sonie rivers create serious problems of flooding, as can be anticipated from their relatively flat loi~g profiles in the lowlands, which serve as flood plains. Thc extremes of' variability in flow are the general characteristics of most of the rivers of Sri Lanka, and many that rise mainly in the dry zonc may dry up completely for a l'ew mouths of the year.

WATER RESOURCES OF SRZ LANKA

(Numbers in circks indicate river bosins listed in table 2 . 2 )

1qigul.e 1.2: Iliver basills of SI-i Lanka.

S PRLITHA MAiVCHsWAYNiB & C.M. 1L1ADUllMA L3ANUM.4

Climatically, the Island is subject to two monsoons, namely, the South- West monsoon prevailing from about April to September, and the North-East monsoon from around October to March. On the basis of distribution of rainfall, the island has been conventionally divided into two distinct areas-the Wet and the Dry Zones (Fig.l.2). The wet zone-dry zone demarcation has been generally accepted as the 2000 mm annual rainfall isohyet. The wet zone comprises the South-West area covering about a quarter of the island, extending southwar-d from Chilaw and terminating with Kandy and Nuwara Eliya in the East. Tl1e Wet Zone, with its two rainy seasons and a n average annual rainfall of around 2400 mm (95 inches), is well developed, with crops such as tea, and coconut and, to some extent, paddy. The remaining three-quarters of the island comprises the dry zone, which has only one major rainy season, extending generally from about October to January. The dry zone has an average annual rainfall of about 1450 mm, and the area contains a small arid area as well as a dry region, and is well suited for irrigated agriculture. In te rns of rainfall received, the use of the term 'dry zone' is a misnomer, which even causes psychological barriers to its development.

Sri Lanlca can be dividedin terms ofrelief into two main regions, namely, the low country, occupying about four-fifths of the area, and tile hill country, occupying the remaining one-fifth. A three-fold division is also possible on the basis of' altitude alone, into lowlands, uplands and highlands (Fig. 1.3 1. I11 tit is classification, the coastal areas of the low country below 100 m in altitude arc considered as the true lowlands, and this portion of the land has practically no prominent hills. The land classified a s uplands can be considered as that lying between LOO and 500 m in altitude, and consists of a varied terrain, with many undulating stretches broken only by low isolated hills. The hill country proper is roughly above the limits of the 500 m contour, and it has been referred to as a remarliably compact elevated mass, rising somewhat abruptly rouncl its edges. The hill country can be divided into three portions ofvery unequal size, nan~ely, the main mass ill the centre, the Sabaragamuwa ridges to the south-west of it and the Knuckles ranges to the north-east. Tbc, main mass of the hill country consists ofa series of high elevated plat1urrns wiLh hills and ridges. 'Phe~.e are over 150 mountain peaks between 1000 and 2000 m, and around twelve pealss between 2000 and 2500 m. The highest peak, though not by any means the most imposing one, is Pidurutalagala, which rises up to 2525 m in altitude. I t only rises about 500 metres from a plateau close to Nuwara Eliya, which is almost 2000 m above mean sea level. Of the other mountains, the more prominent ones are Kirigalpotta (2395 m), Totupalalcanda (2359 m), Sri Pada (Adam" Peali) (2238 m) and the Kikilimana (2238 m).

WATER RESOURCES OF SRI LANIL4

sea level I ml

km. 20 10 0 20 40 60 80 100

Scale

The distinctive plateau areas are :

(a) A series ofhigh plains between Pidurutalagala and Kirigalpotta, such as Horton Plains, Moon Plains, Elk Plains, Wilson's Plains and the Nuwara EJiya Plains, rising in certain parts to heights of over 2000 m.

(bl The Hatton Plateau, whose average height is between 990 and 1200111 &om which the head waters of the Mahaweli Ganga rise.

(c) The Uva Basin, whosc average height is around 900 rn dissected by t w main streams namely, the Badulu Oya and the Uma Oya wliich. form tributat'ies of the Mallaweli Ganga.

Cd) The Kandy plateau, whose average height is between 600 and 900 ni, having several peaks and ranges, as Hantane.

A wide variety of soils is found in Sri Lanka and their distribution is determined largely by the topography and climate. The major soil types include Reddish Brown Earths, Non-calcic Brown earths, Red Yellow Podkolic Soils, Red Yellow Latasols, Immature Brown Loams, and Low Hu~nic Gley Soils. Of these types Reddish Brown Earths culler the largest extent of land atxa occitrring particularly in the dry zone.

1.3 GEOLOGICAL EASE

About nim-tenths of the island are underlain by Precambrian clystalliuc rocks made up of three units. They are: (i) the Highland Complex in the centre, occupying the central Highlands and the NE-trending parallel ridges which extend to Trincomalee; (ii) the Vijayan Complex to the east of it and occupying the eastern and south-eastern lowlands; and (iii) the Wanni Complex occupying the north-western and northern lowlands.

The Highland Coinplex is made up of high-grade mctatnor*piiic ~.oclcs consisting of' quartzites and quartz schists, marbles, quartzo-feldspathic and charnockitie gneisses a ~ l d basic ~vcks. All these rocks are wcll foliated and banded. Jointing in several directions is a common feature, especially of the quartzites. The rocks are highly weathered, especially in the south-western a ~ l d central parts of the island, and here a thick, weathered mantle of lateritic clays and lithomarge rests on top of the bedrock.

The rocks in the Vijayan and Wanni complexes are mostly, granites, granitic gneisses, migmatites and gneisses which are generally not so highly

Lowlands ~ 3 0 5 1

Highlands 7915m

Dry Zone

Inhrmediah Zone

Wet Zone

Figure 1.4: Main geological formations.

12 PALITHA MANCHANAYAKE & C.M. MADDUMA BARIJIAlt.4

weathered. However, jointing and fracturing are present in these rocks, too, and though impervious, groundwater is present, especially in zones of jointing and fracturing.

Jointingin all these rocksplays animportant part in water supply, in the occurrence of springs , and in influence on landforms; the rock types influence the types of soils present in different parts of the island.

Overlying the Precambrian rocks in the north-west in a broadcning belt along the North-western coast, from Puttalam to Jaffna, is a sequence of sedimentary limestones and calcareous sands of Miocene age. Along all tho coastal areas are sands, sandstones, clays and gravels of Quaternary age, tho coastal sands, especially, providing lenses of freshwater,

1.4 LAND RESOURCES AND THEIR UTILIZATION

The total land area of Sri Lanka is about 6.5 million ha or 16 million acres. Of this about one-third has been utilized for plantations and a,urie~xltural holdings. A little over 115 is under woodlands, and about 6.4% under grass and scrublands. All other uses cover about 30% of the total land area. The drastic reductian in land under forests from 44% in 1950 to around 22% today, bad serious implications on water resources.

Land in Sri Lanka is predominantly under State ownership. It has been estimated that over 80% of the total land area of the country comes under the ultimate ownership of the Government. (Table 1.1)

TABLE 1.1: Ownership of Land.

Total land area of the country 6,570,134 100

Land under the ultimate ownership of the Government 5,403,899 82.3

Land awned by the private sector 1,166,235 17.7

So~irce: Land Commission, 1990

VATER RESOURCES OF SRZ LANK4 13

With the increase of population during the recent decades, land per person has declined rapidly, and with a present population of over 18 million, per capita land available is now less than half a hectare. However, the per capita availability of cultivated land was as low as 0.13 ha at the last (1982) Census of Agriculture. The resulting encroachment of State lands and the intensification of agriculture. has significant impacts on the water resources of the Island.

1.5 AGRICULTURE

Sri Lanka's economy has been based on agriculture from ancient times, and it will continue to be the primary source of the nation's economic activity for many more decades to come. The presence of highlandsin the centre ofthe island has resulted in a variety in agricultural production. Tea, whichis a major export crop of S r i Lanlra, is gruwn extensively in the upper altitudes and rubber is grown a t lower altitudes of the highlands. Coconut is the main crop grown along the coastal belts of Sri Lanka, and paddy cultivation has been carried out for several centuries on the plainsa

Since the early 1940s, Honourable D.S.Senanayake, the then Minister of Agriculture and Lands, who subsequently became the first Prime Minister of Sri Lanka, started irrigation settlement schemes such as Minipe, Yoda Ela, Minneriya, Gal Oya, Elahera and Allai-Kantalai. In these schemes, settlers were given plots of both highland and lowland, with facilities for i

r

rigation. This attempt has proved to be successful in diverting a significant portion of the populatiun to unutilized lands which had been sparsely populated in the past. These settlemc~its were ful-ther consolidated by the restoration of additional irrigation reservoir projects such as Uda Walawe, Rajangane, Kaudulla and Pimburettawa, Muruthawela and Muthukandiya, Inginimitiya and Lunugarnwehera. The biggest boost for the settlement of people came with the Mahaweli Development Programme, with its targeted extent of land to be developed, being a s much a s 360000 ha (or 900000 acres).

1.6 POPELATION AND TRENDS

In ancient times, Sri Lanka had supported a larger population than tijday, Some liistorians believe that i t had exceeded 20 million a t one time.

After the establishment of British rule in Sri Lanka, the country had a population of 2.4 million in the year 1871, which gave a density of 37 persons per kmz. By 1991 it had exceeded 17 million, with a corresponding density of about 241 persons/km2. The gradual increase of population from 1871 upto 1981 is given in Table 1.2.

14 PALATHA MANCHANAYAKE & C.M. M.Ql>UiC-fA BANDtLI2i1

TABLEl.2: I-'opulation (in thousands).

Census Year Total Males Females Number ai' Persons/km2

Thcfuture increases ofpopulation are based onthree dif'fcrcnt p~.ojcdions, namely, "high" "mcdium" and "low". Accordingly, they havc becn cornputed as 24.7 million, 21.8 millioll and 19.3 million respectively, by the year ZOO1 A.D.

The urban-rural distribution of the population for the year 1981 has been estimated a t 21.5 % and 78.5% respectively. The urban population has been categorized as those living in the areas-governed by Municipal, Urban or Town Councils. The rest of the population of the country is treated as rural. The migration of people was generally from the Wet Zone to the Dry Zone, particu- larly to irrigated settle~nents (see Fig. 1.5). This was largely due to water resources development efkrts in the past. There is also a significant migration trend towards Colombo from the rest of the country, due to its commercial and urban attractions. At the sarne time, a trend of migration fiom Colon~bo to its suburbs is also taking place, due to ovcr-crowding. These trends c~ea te sigt~ifi- cant demands for domestic and industrial water supplies.

1.7 EMPLOYMENT PATTERN

A major difficulty associated with Sri Lanka's modest rates of economic growth has been the lack of economic opportunities for the growing labour force. Evcn though p e a t emphasis has been placed in the developnlent of new agricultural lands, especially under the Mahaweli Programme, for the settlcrs to earn their living as peasant cultivators, this has helped to ease the unemploy-

merit problem only marginally. Agriculture can accommodate only a minor fraction of the expected population growth of Sri Lanka. From Table 1.3 it can be tloted that the labour force in Sri Lanka will increase to about 9 million by the year 2001,

TABLE 1.3: Laboui* FoiScc: Projection for Sri Lanlra (in Thousanrls). -

Year 1971 1981 1991 2003.

Total 4434 5954 7544 9145

(Source: Del~artnrent of Census and Statistics, Colornho)

TABLE 1.4: Employed Population Classified by Industry (Major Divisions) and Sex (1982).

Industry (Ma.jar Division) Number (thousands) Pcscentage

'i'otal Male l'ernale ToLal Male l'ci~ralc

Total Employed

Agriculture, Hunting, Forestry and Fishing

Mining and Quarrying

ElecLricity, Gas & Water

Construction

Wholesale and Hetiui Trade and Restaurants and Hotels

Transport, Storage and Communications

Financing, Insurance, Real Estate and Business

Con~rnun~Ly, Social arid Pcivol~al Scrviee

Activities not adequaLcly defined

Figure 1.5: Voi~u~ie of iifetinle migratio~l from district of birth to district of

enumeration of more than 10,000 migrants (1981).

WATER RESOURCES OF SRZ LANK4

1.8 INDUSTRY

Even though presently Sri Lanka is not an industrial country, its industrial activity has assumed increasing importance in the national economy over the past 25 years. Industries have been set up and are in operation for the production of' cement, sugar, ceramics, paper, leather goods, plywood, textiles, glassware, tyres and tubes, chemicals and hardware. Sri Lanka has relatively few natural resources and raw materials required for the manufacture of consumer goods, and some of these have been exploited. Significant mineral discoveries of rock phosphate a t Eppawala in the north-central part of the island and iron-ore deposits with substantial copper content a t Seruwila in the East have been made. The graphite mines in Sri Lanka, namely, a t Kahatagaha (off Ibbagamuwa, near Kurunegala) and at Bogala (off Kotiyakumbura, near Kegalle) have been in operation for a number of decades. Ilmenite, zircon and rutile from beach sand deposits in the Eastern coast have been extracted and exported as raw materials during the last few decades. The National Salt Corporation has been operating Salterns a t Hambantota (in the Southern coast), Puttalam (in the North Western coast) and Elephant Pass (in the North). High- grade kaolin deposits are the basis for a highly developed ceramics industry producing table ware for the world market and sanitary ware, electrical goods and wall tiles for the local market.

A start had been made in the petrochemical industry with the establish- ment ofthe Petroleum Refinery, which has a daily rated capacity to process 5200 tons of crude oil. The refinery is functioning under the State owned Petroleum Corporation, established in 1961, which has expanded its activities to cover bunkering, aviation refuelling, marketing of agrochemicals and manufacturing of by-products such as bit~imen, liquid petroleum gas and insecticides.

Industries for the production of soap, vegetable oils, synthetic textiles, asbestos products, bicycles, radios, plastic goods and confectionery have been set up by private sector organizations. The Free-Trade Zone established by the Government recently, has promoted a number of industries by private-sector organizations. In recent years, the policy of privatization has been pursued by the government with regard to uneconomical public enterprises, These new trends in industrial development have led to greater demands for water supply and power generation.

1.9 TICANSPOIW AN11 COMMUNICATION

Transportation within the island includes road, rail and air transport. Rivers and canals were used for navigation in the past' but they do not form a significant medium of transportation today. However, the "Dutch Canal" still

operates between Colombo and Puttalam. This is a canal built by the Dutch when they were ruling the coastal belt of Sri Lanka, and it has been used fol. transport of goods to Colombo. Even at the present day, it has been identified as a cheaper mode of goods transport, and steps are being considered for developing and cleaning this canalway and popularising its use.

I t must be observed that Sri Lanka has not utilized its potential fbr water-based transport. If the bulk of heavy goods can bc tra~~sported by canals, rivers and the sea, much of the congestion on roads can be relieved.

The length of the public roads network maintained by the gove~'nment totalled upto 26004 km by 1993. The roads are generally surfaced with pre-mix bitumen or asphalt. The railways in Sri Lanka are entirely Govei.nment owned and thereis a totaltrack length ofover 1453 km traversing the island. Over 3000 shipping vessels arrive in Sri Lanka every year through the three principal harbours of Colombo, Trincomalee and Galle. This has increased rapidly with the liberalization of imports in recent years.

Sri Lanka's communication system includes the postal, telegraphic and telephone service as well as an overseas telecommunication service. The total number of postal and telegraphic offices in the Island exceeded 4000 by 1993. International Direct Dialling facilities are now available a t most of the mnin cities and towns ofthe country. The use of facsimile and e-mail are incrcsingly becoming popular.

The broadcasting network operates a number of national and provincial radio programmes in Sinhala, Tamil and English. There are also a Commercial Service, a n Overseas Service and an Asian Service in several languages. Sri Lanka also has a national television service coming under several channels, such as, the "Sri Lanka Rupavahini Service", the "Independent Television Network" (ITN) and the Maharaja Television Service. This network is still expanding.

CHAPTER TWO

Water Resources Availability

2.1 HYDROLOGlCAL INFORMATION

Compared with other developing countries, Sri Lanka has a relatively dense hydro-meteorological network covering the entire island, and records have been maintained for several decades. The main governmental agencies respon- sible for the collection of hydro-meteorological data are Irrigation, Meteorology and Agriculture Departments.

In the Irrigation Department, a separate branch was established around 1943 to handle all activities connected with surface water l~ydrology. This could be considered as a significant step taken towards the collection and analysis of the water resources data of' the Island on a scientific basis. Since then, the Hydrology Branch of the Irrigation Department has been responsible, amongst others, for the collection and processing of hydrological information a t about 80 major streamflow-measuring stations, and 14 free-surface pan-evaporation stations, I11 about 60 stations rainfall is measured on a continuous basis on self- recording gauges. There are also over 100 reservoir-level observation stations.

The measurement of'rainfall in Sri Lankadates back to the 19th century, when the British, who introduced the tea plantations, began to keep records of the daily rainfall measurements in tea estates.

The Meteorology Department maintains the national n~eteoroiogical network, which includes over 500 daily-read rain-gauge stations scattered throughout the Island. Some of these stations have records for more than 100 years, which are valuable in the design of water resources development projects. There are also about 65 stations where self-recording instruments have been installed, and for which pluviographicrecords are available. As most ofthese axe fairly new, the lengths of records available are comparatively short. The Meteorology Department also maintains 22 principal Weather Stations covering the entire Island, mainly established in principal cities or towns. A principal weather station would usually have an automatic rainfall recorder, sunshille meter, dry-and-wet bulb hygrometer measurements for relative humidity, an anemometer for the measurement of wind speed, maximum and minimum temperature measurements, and a sunshine recorder for the measurement of cloudiness.

20 PALZTHA MANCHANAYAKE & C.M. MADDUMA BANDAIFt!

The Agriculture Department maintains a network of meteorological stations (Agro-met stations) essentially for agricultural research. Much of the rcsearch focuses on cropping patterns, crop calendars, crop-water use, soil-plant relationships and crop diversification. Among others, the Department, main- tains a network of' evaporation pans to observe the evaporation from free-watc~. surfaces. The Department also makes assessments of evapotranspiration of' plants a t different stages of growth, including water-balance studies.

The Water Resources Board, which essentially looks after the hydrogeological and groundwater resources of Sri Lanka, maintains records for its own purposes. This work was earlier handled by the Hydrogeology Branch of the Irrigation Department, which had a fully fledged and experienced drilling unit. Around 1977, the Hydrogeology Branch of the Irrigation Department was merged with the Water Resources Board along with most of its equipment and expericnced staff:

The National Water Supply and Drainage Board also has a Groundwater Branch which deals with the investigation and exploration aspects of groundwater of Sri Lanka and maintains some hydrogeological records. Their main interest, however, is the supply of water to cities and towns by the development of municipal, urban and domestic water-supply schemes in Sri Lanka. The Board also deals with water quality aspects.

All activities, such as the collection, transmission, processing, storage and retrieval of hydrological information, come within the field of operational hydrology. In terms of data transmission, two distinct practices in operational hydrology can be identified. In instances where the data is transmitted almost immediately as they are observed by means of radio, telephone or on-line telemetering system, i t is called a "real-time data collection system". When there is a significant lapse oftime between the observation of data and its transmission to the processing office, perhaps one week or one month (being sent by mail or sent manually), then it is referred to as a "non-real-time data collection system," and such data would be considered as historic data. Whether it is a real-time data collectioll system or otherwise, all operational hydrological inforn1atio11- generation activities are based on the operation and maintenance of' a comprehe~lsive hydrometric network. Such a network would supply information onrainfjll, stl-eam flow, c\raporatio11, reservoir storage and groundwater depletion or accretion. Most of these variables are interconnected within the fraincwor~ir of the hydrologic cycle, and if a bounded system in space such as a river basin is defined, then a water-balance equation established over a specific time-step would quantitatively relate these variables to one another.

WATER RESOURCES OF SRI LANK4 21

Sri Lanka has 103 distinct river basins, and most of the main rivers originate in the hill-country and eventually flow into the sea, passing tl~r'ough the lowlands. Rivers and streams in Sri Lanka exhibit a remarkable variability in their morphology, climate, soils, land use patterns, geology and drainage basin size. These drainage basins vary in size from about 9 km2 to more than 10000 kmVTable 2.1). Of these, some are perennial, while the others are intermittent. Fig. 1.2 gives a map of Sri Lanka showing the river basins, and it also shows the 2000 mm mean annual isohyet which demarcates the boundary between the Wet Zone and Dry Zone of Sri Lanka.

The density of the hydrometric network would be an indication of tllc adequacy of the number of stream-gauging stations in a basin or a given area, and is indicative of the financial, manpower and other resources on which the government or a responsible organization can invest. The World Mctcorolugical Organization (WMO) has set certain desirable minimum densities of hydrometric networks in their publication "Operational hydrology, Report no 8". The quality of hydrological data being collected would obviously depend on the reliability of the observations made and the nature of the station. In Sri Lanka, there are about four types of stream-gauging stations, namely:

(a) water-level observtltioils made co~ltinuously by an Automatic Water Lcvel Recorder (AWLR) fixed at a specific site;

(b) hourly readings of~vatcr levels taken manually round the clock;

(c) hourly readings of water levels taken manually, but only during daylight hours, namely, from 7.00 a.m. to 5.00 p.m.;

(d) only two manual readings per day, generally taken between 7.00-8.00 a.m. and 5.00-6.00 p.m.

In cases (b) to (d), the quality ofthe data depends on opeleator reliability.

TABLE 2.1: River Basins in S1-i Lanka

Basin Name of River Catchment No. Area km2

1 Kelani Ganga 2292 2 Bolgoda Ganga 378 3 Kalu Ganga 2720 4 Bentara Oanga 629 5 Madu Ganga 60 6 .Madaml~e'Lalze 90 7 Telwutta Gang21 62 8 Katga~na Lake 10 9 Gin Ganga 932

10 Kogga la L:l k r 65 11 Pol watta Ganga 236 12 Nilwala Ganga 97 1 13 Sinimodara Oya 39 14 Kirama Oya 225 15 Rekawa Oya 76 16 Urubolrka Oya 352 17 Kachigal Ara 222 18 Walawe Ganga 2471 19 Karagan Oya 58 20 Malala Oyil 404 21 Embilik:*la Oyil 60 22 Kirindi Oyn 1178 23 Bambawe Aru 80 24 Mahi~silawa Oya 13 25 Uuk~wa Oya 39 26 Menik Ganga 1287 27 Katupila Ara 86 28 Kuranda Ara 132 29 Namadagas Ara 109 30 Karambe Ara 47 3 1 Kumbukkan Oya 1233 32 Batura Oya 93 33 Girilrula Ara 15 34 Helawa Ara 5 1 35 Wila Oya 489 36 Eleda Oyn 611 37 &?randa Oya 4'27 38 Simena Ar3 52 39 'l'andiadi Ara 22 40 Kan~~kacl~chchi Am 57 4 1 Kurus Kulam 35 42 PannelaOya 186 43 Arnbalam Oya 116 44 Gal Oya 1873 45 Andella Oya 528 46 Tumpankeni 9 47 Namaltada Aru 11 48 Mandipattu Aru 101 49 Pnthantodclnlhane Aru 101 50 Vett Ara 26 51 Unnichch:~i 350

(Ref. Fig. 1.2).

Basin Name olLRiver Cntchmcut No. Area lrm'

52 Mundeni Aru 1296 53 Miyangolla Ela 223 54 Maduru Oya 1559 55 Pulliyanpota 53 56 Kirimechchi odai 78 57 Bodigoda Aru 165 58 Mandan Aru I:< 59 Makarachchi Aru 37 60 - Mahaweli Gilng;~ 10448 61 Kantalai Aru 460 62 Palanipotta Aru 70 63 Panna Oya 145 64 Pankulam Aru 380 65 Kunchikumban Aru 207 66 Palakutti Aru 2 1 67 Yan Oya 1538 68 Mee Oya 91 69 Ma Oya 1036 70 Churiyn Aru 75 7 1 Chavar Aru 31 72 Palladi Ar~t 62 73 Munidel Aru 1.39 74 Kodalilcallu Aru 75 75 Per Aru 378 76 Paii Aru 85 77 Maruthapilly Art1 4 1 78 Thoravil Art: HU 79 Piramenthal Aru 83 80 Nethali Aru 122 8 1 Kanakarayan Aru 906 82 Kalawalappu Aru 57 83 Alckarayan Aru 194 84 Mandekal Aru 300 85 Pallavarayan Kadu 160 86 Pali Aru 456 87 Chappi Aru 67 88 P a ~ a n g i Aru 842 89 Nay Aru 567 90 Mavatu Oya IAruv~ AI-uf 3284 9 1 Kal Aru 212 92 Modaragam AIXI 44 93 Kala Oyn 2805 94 Moongil Aru 44 95 Mi Oya 1533 96 Madurankuli Aru 44 97 Kalagamune Oya 153 98 Ratharnbala Oya 2 17 99 Deduru Oya 2647

100 Karambala Oya 596 101 Ratmal Oya 217 105 Maha Oyu 1528 103 Attanagalu Oy;i 736

All Basins 59245

There are some river basins in Sri Lanka where flash floods occur more often than in others, and significant fluctuations in their water levels take place. In such instances the manual observations are preferably replaced by Automatic Water Level Records (AWLR). The Automatic Water Level Recorder chart would indicate the behaviour of the river a t any instance, and it gives a good indication of the response ofthe catchment to an input of storm rainfall, which is useful in the study of catch~nent behaviour. But in the case of hourly readings taker.] manually, it is necessary to plot the instantaneous hourly readings on graph paper and interpolate them to develop the hydrograph. In other words, it is quite subjective. In the case of hourly observatio~ls taken only during the day-light hours, say from 7.00 a.m. to 5.00 p.m., no information ofthe river beliaviour is available for the period fi-om 5.00 pm. to 7.00 am. the followi~lg day. As such, detailed flood studies or the hydrological behaviour of the river basins would not often be possible. Two manual readings taken each day, one in the morning and one in the afternoon, would indicate a very general idea of the behaviour of the river, and this would only suffice for particular catchments which have very slow catchment responses.

A real-time data acquisition system has been i11 operation in the Kelani Ganga basin during times of floods. The Kelani Ganga falls into the sea to thc ilorth of'Colombo, and its floods can inundate considerable extents of'land in the flood-plain. A flood-forecasting system is being used to protect the City ol' Colombo from rnajor floods. The system is generally activated by intense rainfhll on the upper reaches of the catchment and on the flood plains. In this flood- forecasting system, the water levels and rainfall a t different locations of the catchment, namely, a t Glencourse near Avissawella and a t Hanwella and other significant stations, are transmitted to the forecasting centre in Colombo via radio, telemeter and telephone. Accordingly, floodlevels are predicted by the use of a mathematical model and the residents in potential flood-prone areas co~xld be alerted well in advance.

In theimplementation ofthe Mahaweli Ganga Development Programme, the Government of Sri Lanka realized the urgent need and importance of a thorough checking and upgrading of the hydrological data base in the Mahaweli Ganga Development Project area. Although the existing data was found to be satisfactory for an overall planning study, i t was considered lacking in many respects for detailed feasibility studies and for operational water management of the system. Upto the start of the Hydrological Crash Programme, the current metering data was only confined to a depth of flow of about 5 m; anytlzing in excess of this depth was not current-metered. This is primarily because of' practical dif'ficull;ics, of avoiding the risk to life and limb. Thus, all the rating

24 PALITHA MANCHANdYAIa & C.M. MkWDUMA BANllAKA

curves fur the gauging stations of the island were confined to this dcpth of5 m, and all the flood estimatiolls beyond these heights were extrapolated oil' t l ~ e rating curve, thus subjecting to errors,

The Hydrological Crash Programme was started in 1979 to cover the important gauging stations of the Mahaweli basin, and some other areas in the dry zone. At the request ofthe authorities, the project area was extended to cover the South-Eastern dry zone and the Mi Oya basin in mid-1980. In 1983 it was further extended, under Phase I11 of the Hydrological Crash Programme, to the other basins, such as Kelani, Kalu, and Walawe, especially a t the request of the CEB for their studies concerning the hydro-power potential a t proposed reser- voir sites. The above programme was carried out by NEDECO Consultants, with the assistance of the staffof the E-lydrology Branch, Irrigation Department. T l~ is work was funded by the Government of Netherlands, the Europcan Econonlic Community and the World Bank.

The main objectives of the Hydrological Crash Programme were: (i) to collect the high-, medium- and low-flow data; (ii) to check and, where necessary and possible, upgrade the existing data base to establish a reliable long-term data base; (iii) to collect flood data for spillway design; and (iv) to improve the actual procedures of collection and the storage of data. Within the programme area, priority was given to those stations, existing or planned, where data was most urgently needed for planning and design studies of the major watclr- resources development components of the Mahaweli Ganga Project. I11 ordcr to achieve these objectives, the main activities that were carried out undcr the Programme included the selection of sites for current-metering, river gauging and rainfall stations, installation ofhydrometric equipment, including overhead cableways, to monitor higher flood discharges, the training of local staff and the use of such equipment, review of rainfall data and preparation of a rainfall reference base to the Project area. They also included the collection, processing and storage of old and new data on rivcr stages and current metering with the aid of the computer.

Earlier, sediment studies (silt in transport) were carried out by using the US DH-48 deptll-integratingsarnplcrin: ( i ) the Walawe Ganga a t Samanalawcwa and Embilipitiya; (iil the Kirindi Oya a t Lunugamvehcra; and (iii) the Mahaweli Ganga a t Morape, Elahera (10.5 mile post), Gurudeniya and Kandakaduthurai. Bed-load sampling was taken at Gurudeniya using the pressure difference type of bed-load sampler developed in the Netherlands. In cases where silt in transport was taken, arating curve was developed and the bed load was assumed to be 10% of the silt in transport for the corresponding discharge.

WATER RESQlflZCES OF SRI W K A

2 EMNl?&k THE SOURCE OF WATER

Pmcipitatioa-is the ultimate product of a series of atmospheri.cproce~sm. kt Srii Lanka, precipitation is almost entirely in the form of rainfall. A smdl quantity is received as dew and occasionally as hail uv frost a t high devatims, Ilril mmes in lumps 'a bulbs of ice over 5 mm diameter, formed by alternate freezing or melting as they are carried up and down in highly turbulent air currents, Dew is generally the moisture inthe atmosphereconden%& on exposed scu'faces, especially a t night, Rainfall comes mainly in two forms, namely, in mf11:zzlc when the size of water droplets is under 0.5 mm and its intensity is Less 6

than 0,Ol mm/h, and rain when the.size.of the drops is more than 0.5 mm: The upper size of a Water drop is generally found to be about 6.25 mm, as hops greater than Chat tend to break as they fallthrough the air,

f he mean annual Gainfall over the ~s land is about 1800 m, with certain parts such as Mamar and Hambantota (the arid region) receiving about 900 mm, and certain parts in the hill country exceeding 5000 niym (see Fig.2.11, The larger totals are generally recorded in the western slopes of the central hill country; srndler valugs are found in the North-Western and the Sauth-Ea&erl~ coastal lowlands.

I'he total annual fainfall is distributed 6ver two main ~grirtulhral seasons, viz,, the wet-season and the dry season, The wet season rainf~ll (usually this season is referred to as the Merlra 'season for nx1tivatisnpurpasmS or North-East monsoonal.rainfall, generally varies from 800 mm to about 3000 mm, where peak coacentt"a;tions occur along the Kducklet3 Range..pf hills, and lowest rainfall occum in the north-western and south-eastern lowlands. The dry season rainfail (usually this season is referred to for cultivation purposes as the Yala season) or the SouthrWest m~nsoonal rainfall, varies from 150mm t o about 3000 mrn where large rainfall occurs on tliewestern slopes of the central hills, and the lowest rainfall occurs' in the north-Gestern ahd south-eashrn lowlatids.

.. be weak he^ patter?~~'&id~e associat&drainfall& be dividedinto four

distinctive categories, namely, those oE (a) the Nmth-East Monsoon, Cb) South? v West Monsoon, (c) the mnvective cloud or thunderstor&, and (d) the pattern of

weather caused by &pica1 depressions in the neighbourhood of Sri Lanka The North-East Monsoon occurs generally from December to Febmwy-, while the

0

South-West Monsoon c~messusually in the period from May to September, The thunderstorms ur cofi~ective clouds occur during the f i s t inter-monsoonal period, namely, from March to April, and the depressions take place during the second inter-monsoonal period, from October to November. The Indian sub- continent dominates th& weather pattern in Sri Lankregion due to the extent of its land mass. During the northern summer, the landmass is warmed and a

WATEl? RESOURCES OF SRZ LANh2 2 7

'low' develops in the north-west of India. During the northern winter, the land mass is cooled and a 'high' develops over India. The Inter-Tropical Convergence Zone (ITCZ) moves northwards and lies over the Gangetic Plain in July a t the heighh of the northern summer. The ITCZ moves southward during the northein winter, and lies between 5 and 10 degrees South in December. Thc ITCZ moves across Sri Lanlca twice during the course of a ye

ar, firstly in its northward

movement and secondly in its southward movement.

The thunderstorms nornially occur during the first Inter-monsoonal period, namely between March and ApriL They are the result of' convective processes that are taking place in the atmosphere during this period and the surface ofthe earth is heated by radiation received from the sun. The air near the earth's surface is warmed and the warm air rises. The moisture in the rising air condenses to form clouds and the maximum heating will be in the afternoons; thcir maximum developn~ent will also be in the afternoons, as such, rains from these clouds would bc usually in the afternoon, and sometimes they may continue into the evening arid night. The requirements for convective cloud develop~nent are heating of the surface of the land and a moist and an unstable attmosphcrc. Tl-ie other f:actor.s that enhance the rising air include its movement over hilly ground, and the convergence caused by the friction of' the su

r

faces. During April, with the approach of the ITCZ on its northward movement, thunderstorms are widespread and more frequent, especially with cyclo~~ic disturbances.

The ITCZ is normally over Sri Lanka in May, and moves northwards, crossing the Island by the third week in May every year. With this there is a cl~ange in the s~zrface atmospheric pressure, and a south-westerly pressure gradient is gradually established across the Island.

Evening thu~~ders torn~s continue during May, with some showers over the south-west coastal areas of tl~eIsland in the mornings. The showers are due to the mild westerly winds. Once the ITCZ has crossed Sri Lanka in its movement northwards, the Island comes under the south-westerly air stream, heralding the period of the South-West monsoon. The gusty weather during the South-West monsoon occurs when a steep, south-westerly surface pressure gradient forms across the Island due to depressions formed in the Bay of Bengal. The pressure gradient is sometimes due to a deep trough of pressure in the Bay. In these instances, the rains are widespread, covering the south-west quarter of the island, the central hills and parts of the North-Western and North-Central provinces. The showers are scattered and generally occur in- 'the south-west quarter of the island. The orography, too, plays an important role. The nioist air is lifted arographically by strong winds and releases moisture on tho windward side. Generally, the maximum rainfall is experienced rnid~vay along

28 PALITHA M A N C H A N A P . & C.M. MADDUNA BANDARA

the slopes of the hills on the windward side. In Sri Lanka, the maximum rain appears to occur at altitudes between 600 and 1200 m on the windward slopes during- the South-West monsoon. The rainfall decreases during July and August. The rainy spells during these two months are due to low-pressure circulations in the middle atmosphere. Isolated thunderstorms are reported in the eastern parts of Sri Lankajust preceding the rainy spells. Moderateto henvy rainis experienced over the western slopes of the central hills during these spells of rain. The monsoonal conditions generally persist during Septcmber, too.

The second Inter-monsoonal period is from October to November, and the ITCZ is near or over Sri Lanka during this period. The rainfall is widespread and this is mainly due to the passage of low-pressure systems, depressions and cyclones near and over Sri Lanka. The low pressure systems that form the ITCZ move along it and give more widespread rain than those caused by cyclones. The tropical depressions originate as low-pressure areas on the ITCZ during October and November, and this low-pressure area may move along or form into a deprossioil with a wind circulation in an anti-clockwise direction, and breali away from the ITCZ. The muvements ofthese systems are generally in a westcrly or north-westerly direction in our latitudes.

The North-East monsoon in Sri Lanka is generally operative in the months of December, January and February, and the surface atmospheric- pressure gradient is northerly across the island and almost the reverse of that of the south-west monsoon. It is found that the tropical easterly winds move in a wave from east to west. These are accompanied by changes in the atmosphuric pressure, and the pressure changes also occ~w in the same dircdion. T l~c direction of the wind at the surface and at higher levels in the atmosphere is not nurth-east always, nor is it easterly. The direction often ehangcs from north-east to south-east and back, indicating a trough formation. The narth-east monsoon rainfall will depend on the passage and the frequency of the troughs across the island. The tropical easterly winds in our longitudes gradually move southward towards the equator. This movement is caused by the high pressure that forms over India during the Northern Hemisphere winter.

Thc various weather patterns generally affecting the Island have been disc~~ssed in the preceding pzragraphs. There are changes in this general pattern from year to year, and season to season. However, a rernarltabl-e uniformity is noticed if rainfall during these particular periods is examined.

The rainfall in Sri Lanka during the North-East monsoonal period benefits a larger portion of the island than during the remaining part of the year, The South-West monsoonal rainfall, though received in greater amounts, ben- efits only a small portion of the island

WATEl? RESOURCES UP SRI LdWK4 29

Tfic monsoonal rains are mostly dependent upon the prevailing winds during both the sbuth-west and north-cast monsoons, and the annual averagc rainfall varies from below 900 mrn on the north-western and south-eastelm fringes of'the island to about 6000 mm a t certain placcs on the souti?-wcstcrn windward hill slopes. As noted earlier the "dry zone" and "wet zone" are generally demarcated by the 2000 mm annual average rainfallisohyet. The4'wet zone", which receives the major portion of its annual rainfall during the south- west mansoon, covers approximately the south-west quadrant of the island, From the hydmlo@cal point of view, however, it appears more rations11 to def-inc the "dry zone" as an area where the average annual rainfall is less than tile average annual potential evapo-transpiration. This implies .that tilere con be little or t ~ u run-off ifthe rainfall is evenly distributed throughout the year as thc potential evapo-tx-anspiratio~r ranges from about 1800 mm to 2000 Irlm pwrycsr in t h e low-altitude areas of' tl're country. This may then g ~ v c u pbysienl representation of theSdry zone" and "wet zone" demarcation also, where tlw "wet zone"is the area ofthe country that has a net surplus ofrun-offover the potential evapo-transpiration during the year.

The wet zone generally encompasses the south-western plains and tha mountainou9 quarter and cvvers a n area of about 12205 km" The rainfall is somcwhat evenly distributed during the year, with the maximilnr rainfall recorded during the south-west monsoon in the mvnths &&Lay and 3 unc. Tlrc agricuitural develupment in this zone is mainly by rain-fed cultjvation together with 8 few :cnietik schemes ~fivet-ting the strcnmtlaw, without any il~igatiut~ storage reservoir.^. T11c cultivation in the lowlands had gcrlerally been paddy with mostly double-cropping. These have been quite successful in tile wet zone, despite there being no storagereservoirs, because ofthe reliability of the rainfall in the area. The rivers flowing with their entire course in the wet zoas arernostl y perennial, and they account for a mean annual yield of22843 mcm, which is about 49% of'the total mean annual yield of all the rivers of Sri Lanka. But the wet zone catchmenti3 total only upto about 19% of all catchment areas ofLSri Lanka, This gives anidea of the degree ofwetness ofthecatchmentnts in thiszone.

Tl~e dry zone, which covers the remaining 80% of the islai~d (includiag intermediate zone), with all alvu of a b ~ u t 52385 km%xhibitswide variation^ ill

average allizual precipitation and run-&and also in their spatial distributior~- The variation of precipitation and run-offabout the mean in the wet zone is rrr ueh

C

smaller than that af the dry zone, which signifies the lesser reliability of rr111-off' in the latter. Even though the precipitation and run-off are less reliablepit should be emphasized that a major portion of the valuable land resources with appro- priate soil grpupsf~agriculture are availablein the dry zone ofthe country. This signifies the need for trans-basin diversion and the construction (sf a mttltitude of' ~ ~ s e r v o i r s to store watet* for iirigation as in the case of the Malsaweli Development P1.qject.

Analysas. of rainfall d a b in St3 Lanka since the end of the I ~ s t century indicate the eedtc~iee of certain secular trends. Thus Thambiahpillay (25157) mcogniizecl "wet" and "dry" phases iri inter-annual variwtions ill rainfall occul'- ring ~y~lfcally in periods of' approximately 20 years:

Up to 11880 - Dry Phaw $882 - 19UU - Wet Phase 1902 - 19210 - Dly Phase 1921 - 1940 - Wet Phase 1841 - 1960 - Dry Phase

Re attempted -to interpret these trends in relation to nsnspot cp~les. Howe.ver, sulssequmxt workers in the same Geld, suck as Hamamori C1987), did nut subscribe Lo tile sameview, Nevertheless, it was shown in same r.ain-gaaging s t a t im that, there is a definite declining trend of annaal rdnfrrli dtuing%l~e last hundred years (MaddumaBmdars&fE;uruppuarachchi 1989). Thus, at Nuwar& Eliya, thore lzad been a 20% decline in annual rainfall since the 1870~ (Pig. 29) . att-ra~tgiir somu WI-itel-9 (I-Iamarnori,l967f attempted b 11E1k this tratzd with lllc expansicriz of tea plantations in the hill eoutit~y, a mure plaitsiblc expl aslation i6 yet to b~ found. The most reoent studies (Kay- L.t: al. 19831 iilciicatt+ that, the significant dacline ofrainfall in the hill country c m be rdated to global wa~ming and tire rise 6f .sea surfam tempemtures in the surronndiag Indian Ocean.

24- SURFAGE WATER RESOURCES

As noted earlier, there are 1103 river basins which have )Jae,.n di&inctt;Iy identified in: Sri tmka, covering a total land area of 59245 knr'. Tl~u JdSha Pe~~nsula , which is virtually devoid ofrivcr basins rtmers about 5558 km*. "Ylit. h t d intea*-basin aiea nc?rrrtl~c coastlineis estimatedtt) he a~c>ururt 1 O L H krn? &it of'thc! 103 river hasins, there arc a fair number ofsmall ~atcthmernts, nrostly less &.an 100 Irm2 in area, where regular stream gauging has not been done, mainly due to economic reasons md/or practical difficulties.

Thra river basins of Sri Lank8 vary in size, from about 9 sq km tv more than 1EPO00 ~q km (Table 2.11). Their Iengths also vary, with the longest being Mahmeli with a length of 335 km. The M d ~ a t u Oya, which ra14ca wcs~~nd, i;: about 164 km inlm~gth. Water resources availability by river basins is in Table 2.2,

WATER RESOIfIEGES OF S f i " l W R d

32 PALZTHA MANCHANAYAKE & C.M. MADDUMA BAND&

TABLE 2.2: Water Resources Availability in Sri Lanka. Mean Mean Annual

Bas111 Name of Basin No-of' Catchment Annual Annuit l Dischilrgt* No. R ~ v e r Area Precipitation D~sch;~~'gc, IS>^'/, o f

Gauging Inn' volume Volumc to p ~ ~ l p t t i ~ t ~ ~ ~ i Stations (mcm) sea ( mcm)

1 Kelani Gahg;~ 09 2292 8660 5.579 64.4 2 Bolgoda Ganga 378 1061 485 45.7 3 Kalu Ganga 05 2720 11302 8183 72.4 4 Bentara Ganga 629 2153 1247 57.9 5 Madu Ganga 60 202 119 58.9 6 Madampe Lake 91 288 112 38.9 7 Telwale Ganga 52 164 89 54.2 8 Ratgama Lake 10 33 18 54.5 9 GtnGanga 03 932 3085 2179 70.6

10 Koygala Lake 65 16 1 65 40.4 11 Polwatta Gang3 236 657 299 45.5 12 N~lwala Canga 04 97 1 2871 1S79 48 0 13 Sinimodara Oya 39 74 22 28.7 14 Klrama Oya 225 44 1 130 29.5 Xi Relcnwa Oy;l 76 105 26 19.0 16 Uruboltlie Oya 352 612 193 32.4 17 Ki~chigal Aru 223 338 c r t , ., Z1.G 18 Walawe Ganga 02 2471 4577 2200 48.1 19 Karagan Oya 58 55 7 12.7 20 Malala Oya 404 474 74 15.6 21 Embalilcala Oya 60 57 7 12.3 22 Kirindi Oya 02 1178 1774 428 24.1 23 Bambawe Aru 80 89 13 14.6 24 Mahasrlawa Oya 13 12 2 167 25 Uutnwa Oya 39 35 5 14.3 26 Menik Ganga 1287 2098 484 23 1 27 Katupiia Aru 87 98 15 15.:; 28 Kurancla Aru 132 149 :3 1 20.6: 29 Nnmilcl;igas A ~ L I 109 122 18 14 8 30 Kal.:~rnl,r Aru 47 52 8 16.4 31 IC~tmbu1tk;ln Oyn 02 1233 1938 4 2s 2%. I 32 Bagura Oya 93 105 16 152 33 Ginltula Aru 16 17 3 1'7.6 34 Helawa Aru 52 81 18 32.2 35 Wila Oya 480 858 218 25.4 36 Weda Oya 611 107 1 394 36.8 37 Karanda Oya 427 752 193 25.7 38 Simena Aru 52 84 20 23.5 39 Tanci~adi Aru 22 37 9 24.3 40 Ka~~gikudichchi Aru 57 94 23 '24.5 41 Kulus Kulam 35 66 13 . ., . 2d.L 42 Pannela Oya 186 358 i r 21.5 -n

43 Ambalarn Oya 117 2 19 G" 28.3 34 Gel Oya 1573 3G40 1679 251 (i 45 Anclell;~ Oya 528 1009 286 28.3 46 'l'humpalteni Tank 9 16 4 25 0 47 Nan~alcada A1.u 12 20 5 25.0 48 Mandipattu Aru 10 1 164 39 23.8 49 Pathanthoddathane Aru - 101 169 42 24.9 50 Vett Aru 26 48 13 27.1 51 Magalavathuvan Aru 350 679 290 29.0

TABLE 2.2 contd.

Basin Name of Basin No. of Catchment Mean Annual Mcnn Annual An,Dischsr.gc No. Rivcr Area Precipitation Discl~al-gc as n % ol'

Gauging km2 volume Volume to precipitation Stations (mcm) sea (mcm)

52 Mundeni Ant 1295 2609 781 29.9 53 Miyangod;l Ela 228 347 75 21.6 54 MaduruOya 1559 2816 777 27.6 55 Palliyantota Aru 53 95 26 27.3 56 ICirimechchi Oclai 78 142 39 27.5 57 Bodigucla Aru 166 304 81 26 6 58 Manclan Aru 13 24 7 29.2 59 Maltarachch~ Aru 38 73 19 26.0 60 Mahaweli Ganga 22 10448 26368 8141 30.9 6 1 Kantalai Aru 45 1 691 149 21.6 62 Panna Oya 70 118 30 25.4 63 Palampotta Aru 145 243 59 24.3 64 Panlculam Aru 381 663 168 25.3 65 Kunchikumban Aru 207 323 72 22.3 66 Pulalcutti Aru 21 32 7 21.9 67 Yan Oya 02 1538 2476 482 19.5 68 Mee Oyn 91 13 1 27 20.6 69 Ma Oya 1036 1500 300 20.0 70 Chunyan Aru 75 109 22 20 2 71 Ctisvar Aru 3 1 44 9 20 5 72 Palladl Aru 62 99 23 23.2 73 Niiy Aru 189 29 1 64 22.0 74 Kocial~lcallu Aru 75 110 23 20 9 75 Per Aru 378 571 122 2L 4 76 Pali Aru 85 121 24 19.8 77 Muruthapilly Aru 4 1 6 1 13 21.3 78 Thoravil Aru 9 1 133 29 21.8 79 Pixamenthal Aru 83 123 26 21.1 80 Netheli Aru 122 167 32 19.2 8 1 Kanltarayan Aru 01 907 1265 242 19.1 82 Knlawalappu Aru 57 72 13 18.1 83 Altlcarayi~n Aru 194 249 44 17.7 84 Mandelial Aru 300 404 75 18.6 85 Pullavananliadu A1.u 6 1 216 40 18 6 86 Pali Aru 456 613 113 18.4 87 Chappi Aru 67 89 16 18.0 88 Parangi Aru 0 1 842 1175 225 19.1 89 Nay Aru 567 719 123 17.1 90 Malvatu Oya 0 1 3284 4573 566 12.4 91 KalAru 212 202 25 12.4 92 Modaragam Aru 943 1100 169 15.5 93 Kala Oya 01 2805 3974 855 21 5 94 Moongil Aru 44 60 7 11.7 95 MiOya 0 1 1533 1925 199 10.3 96 Madurakuli Aru 73 92 16 17.4 97 Kalugamuwa Oya 153 211 38 18.0 98 Rathambala Oya 218 311 62 19.9 99 Deduru Oya 0 1 2647 4589 1129 24.6

100 Karambalan Oya 596 1026 255 24.9 101 Ratmal Oya 218 440 135 30.9 102 Maha Oya 03 1528 4218 1485 35.2 103 Attanugalu Oya 0 1 736 1974 845 42.8 (Source: Ranuturzgu D.G.L., 1974)

An understanding of the total water resources availability of the Island can be obtained from Table 2.3, which summarizes the available data.

TABLE 2.3: Surface Water Resources (average upto 1972).

Wet Zone Drv Zone Isla~ld Total

Rainfall (Annual) (mm) 2424.18 1468.12 1937.00

Rainfall (Annual) cinches) (95.44) (57.80) (76.26)

Run-off (Annual) (hectare meters) 2 . 5 8 x l O V . 5 5 ~ 1 0 " 5.13~10~'

Run-off (Annual) (acre feet) 2O.93x1O6 20.66~10" 41.59~10"

Run-off rainfall ratio 65.1% 35.8% 40.5%

Escape (hectare meters) 2 . 0 4 x 1 0 ~ . 3 0 x 1 0 C ' 3.33~10"

Escape (acrc feet) 1 6 . 5 0 ~ 1 0 ~ 0 . 5 0 ~ 1 0 " 27.00~10"

Escape as a 54. of Run-off 78.83 50.82 64.92

Although different estimates of surface run-off vary, it may be assumed that the total annual surface run-off of the Island is around 5.13 million ham (or 42.00 million acre feet). A considerable proportion of this is already utilized, particularly for irrigation and hydro-power, and what escapes to the sea is less than 3.33 million ha m (or 27 million acre ft).

Therc is no detailed water-balance study covering the entire island. However, certain general observations can be made from Tablc 2.3. For instance, i~ is observed that almost 50 "/c of'the surhce waters oftlie dry zone arth utilized. With the impleme~ltation of development programmes in this arcn, particularly the Mahaweli Development project, it is likely that the estimated surface water resources ofthe dry zone would come down to about 30- 40% ofthe total run-off. From the annual average rainfall of nearly 2000 mm for the entire island, around 5 million ha m or 40%, appears as surface run-off. Of the balance 60%, around 20% infiltrates to replenish soil moisture and groundwater bodies. This is confirmed by studies on direct recharge fromrainfall arrived theoretically as well as by direct mesurements usingradio-isotopes (de Me1 & Sumanaselrera, 1973; Dharmasiri, Dharmawardhana & de Me1 1985; Fernando 1973 ). Thc balance 40 cii- is returned to the atmosphere through evapo-transpiration.

WATER RESOURCES OF SRI LANKA

2.5 GltOUND WATElt RESOURCES

Sri Lanka is an agricultural country and its water requirements are met mainly by surface-water resources. The surface-water reservoirs are replen- ished from rainfall and run-off from streams. In the dry zone, which occupies about 80% of Sri Lanka's landmass (including the intermediate zone), the rainfall is generally prevalent only in the Maha season, and for the most part of the rest of the year it is sunny and dry. The water collected in numerous surface- water reservoirs is being generally used for cultivation during Maha season and for domestic use throughout the year. These reservoirs are used fbr cultivation in the Yala season, only if there is sufficient water to carry over in the reservoirs from the Maha season and supplemental rains in April. From ancient times, people have used shallow wells, dug through the weathered overburden, for drinking and other domestic uses, particularly in the wet zone. Such practices have beenintroduced only more recently to the dry zone; The use of ground water through open-dug wells has come into practice only in the last few years.

Over the past few decades there have been numerous occasions when the monsoonal rains have failed, resulting in prolonged droughts. The demand for good quality water has increased over the years due to a rapidly increasing population and industrial growth and also due to the requirements of livestock. Consequently, exploitation ofgroundwater commenced in the mid-1950s and the demand fbr i t has been on the increase ever since. Today, groundwater is extracted from shallow dug wells as well as from deep tube wells. The amount ofwater that could be safely extracted from a well depends on a variety of factors, such a s the aquifer characteristics, including porosity, permeability, transmissivity and storage capacity of the groundwater body. The sustainable rate of extraction of a well or the 'safe yield' of an aquifer, would depend on the rate of recharge.

Among the diffkrent types of aquifers, the karst limestone aquifers are regarded as the richest sources of groundwater in Sri Lanka. These aquifers are found in the Miocene Limestone belt that extends from Puttalam, through Mannar and upto the Jaffha Peninsula. As this limestone is porous and cavernous, the water retained on the surface is minimal and a significant amount of water seeps through the limestone formations and stays above the hard rock below the limestone. Drilling through the overburden or the band of limestone, the water-table is encountered and water could be extracted from it depending on recharge. Also, in some places such as Puttalam and Vanathavillu geologic formation, there exists artesian conditions where the water rises above the ground level under pressure. Extensive groundwater utilization is found in the Murunkan, Vanathavillu and Jaffna areas, and in thegaffna PeninsuIa and some islands it has gone beyond sustainable levels.

3 6 PUYrHA MANCHANAYAKL3 & C.M. MALIDUMA BANDAKA

Much of the work on groundwater had been carried out by the Irrigation Department and subsequently, by the Water Resources Board. In the dry zone, the weathered overburden is relatively thin, with a maximum thickness of about 25 m, and it is underlain by the crystalline bedrock. Therefore, the storage capacity for groundwater is limited. Even a t places where the bedrock is fractured, location of wells would be a difficult task due to insufficient availability ofhydrogeological and geophysical infbrmation. The Water Hesourccs Board and the National Water Supply and Drainage Board have lauilckcci a programme to drill tube wells into the crystalline rock, in an attempt to provide good-quality drinking water, particularly to the rural areas. This is donla with foreign assistance, as in the case of' IRDP projects and those by FINNIDPI. In most areas in the dry zone, the groundwater has been found to be of'hard quality owing to dissolved salts of calcium and magnesium. The chances of finding good quality groundwater in considerable amounts are promising in coastal areas and alluvial valleys. In some coastal regions, fairly thick sand deposits form groundwater aquifers, which provide water for domestic and industrial use, as in the case of the Katunayake Free Trade Zone. But considerable care has to be exercised in exploring and exploiting groundwater close to the coastal belt, lcst salt-water intrusion can take place.

In Sri Lanka, groundwater for agriculture has been mainly co~lf i~~cd to the sedimenta

r

y Miocene formations in the Jaffila peninsula and tl.1~ no)-tl-r- western areas, and not much attempt has been made in exploitation of groundwater in the dry zone hard-rock areas until recently. Geologically, 90% of the island consists of crystalline hardrocks, such as granites, gneisses, charnockites, schists and marbles of Precambian age. The remaining land-mass, consisting of sedimentary formations, is confined to the north and the north- western coastal belt. The total groundwater availability in the island has been estimated a t around 7250 mcm per year (Fernando, 1985), which is about 15% of the country's surface water resource.

In the Jaffna peninsula, the occurrence of freshwater is ty pica1 of that of any small island with the groundwater lenses floating over the sea water. 'l'he thickness and the uniformity of these freshwater lenses would be grcally affected by the cavernous limestones found in the area. However, there have been over 100000 dug wells constructed in the Jaffna peninsula, with depths ranging from 5 to 10 m, which are used for small-scale agriculture and domestic purposes (Arumugam, 1969).

The information on actual quantities of available groundwater i n different aquifer formations is still incomplete, except in a few areas where special studies have been carried out. The initial hydrogeological studics were made in 1966 in the Vanathavillu area (north of Puttalam) by Israeli

WATER RESOURCES OF SRI LANIU 3 r/

hydro-geologists, in collaboration with their counterparts in the Irrigation Department. These studies were continued by the Irrigation Department to cover the Mulangavil, Murunkan and Jaffna areas, and they indicated that the Miocene limestones of the north west are karstic, with a high degree of secondary porosity. They extend over north-western and northern coastal areas and the thickness ofthe aquifer formation generally tends to increase towards the coast- line. In the Vanatlmvillu basin, which spreads over some 40 sq km tlzc aquifer is confined and crcates artesian flow conditions in somc areas. The estimates of groundwatel. resources available in the Vanathavillu basin vary between 5000- 20400 million Ilannum, with the latter figure possibly indicating the ultimate potential (Henreck and Sirimanna, 1968; Wijesinghe, 1975; Foster et ul., 1976).

To the north ofvanathavillu is the Murunkan basin, located between the stream courses of Malvatu Oya (Aruvi Aru) and Nay Am. This i,s an area where deep tube-well fields have been developed during the last fifteen years. Here, at depths of 15-25 metres below the ground surface, relatively high-yielding semi- confined aquifer systems are observed. It has been mentioned that pumpilzg rates of19-25 Us are possible, with negligible drawdown in the Murunkaiz Basin (Wijesinghe, 1985). The next major aquifer system, located in the Mulankavil Basio to tllc north ofMannar, lies between the water courses of the Pali Aru and thc Pallavarayan Kadu, covering an area of 180 km? The averagc yields from tube wells in this area are estimated to be in the range of' 15-35 11s (Foster et al., 1976).

In the hard-rock areas of the metamorphic complex, which covers over 90% of the Island, deep regional aquifers are rare. They can only be exclusively associated with special geological conditions, such as the presence of quartzites or marble bands within the metamorphic suite. However, such formations which are fairly isolated, do not account fbr more than 1-2% of the total land area. The problem is however that, as Foster et al. (1977) noted, 'any orw attemptitzg to formrrlute a ~zatior~al policy or1 grozrndwater. development for the ~netanzor-plzic regions ofSri L a l ~ k a is confro~zted with erzorrnorts deficielzcies in Izydrologic data'.

In metamorphic regions, which are almost devoid of extensive aquifers and regional subsurface drainage systems, the long-term groundwater availa- bility can essentially be taken as the local, long-term average recharge rate from rainfall infiltration plus any seepage from existing irrigation systems.

Foster et al. (19761, arguing from first principles, observed that an infiltration of 50 mm would represent a groundwater resource of 0.5 million 1. However, the observedinfiltration rates, as noted earlier, were found to be in the rang-e of 10-30523 oftotal rainfall, giving a recharge factor ofovcr 300 mm. Thus, the opinions on the potential of groundwater resources vary widcly betwccl-I

various investigators. The data from recent groundwater-development pro- grammes under the IRDPs and the Water Supply Authorities, which led to the development of tube wells fbr domestic use in the dry zone, would perhaps be valuable in resolving the many conflicting estimates ofthe actual potential.

Available estimates have indicated well yields in the Vavuniya District to be in the range of 10000-50000 Wd (2000-11000 gpd). In the Colombo district a t two sites, laterites have yielded a total of 0.3 million Wd (67000 gpd) and 0.1 million Vd (22000 gpd). Tube wells drilled up to 25 m deep in Trillcomalee and Hambantota districts recorded yields up to 34560 Wd(7200 gpd). Wells sunlr into quartzite formations, as a t Melsiripura (Kurunegala District) and Kcbilitigollcwa (Anuradhapura District), have recorded yields of'0.43 million 11s lo1. less t11a11 1 rn of draw-down. Where quartzite formations are dissected by transvc~*su valleys, there are significant springs, as observed in the Matale District. The use of groundwater in both limestone aquifers as well as in metamorphic areas is dependent on their chemical quality. Table 2.4 summarizes some data on limestone aquifers. Fig. 2.3 indicates the quality of water in tube wells constructed up to 1985. I t can be seen that in many areas the water from tube wells was found to be ofreasonable quality, but occasionally affected by excessive salinity, hardness or fluoride contents.

TABLE 2.4: Water Quality of Limestone Aquifers

Chemical Parameter Minimunl Value Maximum Valuc Usua l Rangc

( P P ~ ) - ( P P ~ ) ( P P ~ )

Bicarbonate

Chloride

Nitrate

EC 910 4200 1500 -3000 (at 25OC) mhos

- -

(Source: Bc~st~c~ynhe, 1981)

WATER RESOURCES OF SRI LANKA

@ Excess Iron

0 Excess Fluoride

O Saline

@ Hard

8 Excess Nitrate

0 Futher studies to be Undertaken

Figure 2.3: Quality of water in tube wells.

40 PALITHA MANCHANAYAKE & C.M. MADL)UMA BANDARA

2.6 EVAPO-TRANSPIRATION

Evaporation is the conversion of water from the liquid to the vapour state. Transpiration is the process by which plants draw water from the soil to support their life process, the water rises up to the leaves and evaporates from the surface of the leaves into the air as vapour. The total amount of'water passing into the air is measured by using Evaporation Pans. Both the Irrigation Department and the ~~~~~~~~~~~~e Department maintain a nctworlc of evapora- tion pans across the island at some 35 selected stations (Table 2.5). Of these, there are about 18 stations mainly in the Agricultural Research and other stations in Sri Lanka. In addition, the Irrigation Department has a number of evaporation measuring stations located near large irrigation reservoirs. The United States Weather Bureau (USWB) 'A' class Pan is commonly used in measuring free-water surface evaporation.

Table 2.5 gives a list of Pan-Evaporation Stations maintained in Sri Lanka by the State and i t also gives the respective year of comnlencemcnt of'the readings and the organization which maintains them.

When one studies the water balance of a given system, evapo-transpi1.a- tion is the most difficult to measure, much more difficult than rainfall or river flow. Therefore, only a few direct measurements of evapo-transpiration are available. However, indirect methods, based primarily on climatological factors, have been used in estimating free-water surface evaporation, often supported by comparisons with the other directly measuredvalues. In the wet zone, where the dry season is shorter, the water supply to the vegetation root-zone is unlimited. Annual evapo-t~anspiration vai-ies from about 1500 mm to about 1700 mm (Kayane, 1983). In the highest montane areas of Sri Lanka, where cloud cover significantly reduces levels of solar radiation, the corresponding value is 1000 mm.

In the Dry Zone during the Maha Season (October - January), in ail average year with adequate rainfall, evapo-transpiration levels parallel those in the wet zone. However, during the Yala season (May - September), which is a drier period, evapo-transpiration is comparatively lower due to moisture content of soil. Evaporation from tanks in the dry zone is estimated at about 2100 mm/ yr, which is highcr than that in the wet zone.

TABL% 2.5 Ust afE)an-Evaporzrtio~1 Stations, Sri Lanka.

Name tef static& Year of ~o&mencernent Orgmization Maintaining of readings the Station

1, Agdawatta 2. Bandamwela . 3. Batalagoda 4s13ambuwela 5. Col~mba 6 , Eraminiyaya 7. Giant" Tank 8. Inginiyagala 9- Iranamadu 10, Kalawewa 11. &nde Eta 12. Kantalai 13, Kattawa 14. Kundamiafe 15. Kuruwita 16. Lunuwila 17. Maha Illuppallma 18, Mahiyangana 19, Matde 213. Nachchadwa 21. Peradonip "

22. Periyiakalapuwa 23. Punczhimiriswatta 24, Ratnapura 25. Rajangaae 26. Ridiyagama 27. Sita Eliya 28. Tabbowa 29. Talawakelle 30. Tirunelveli 31, Tiasa 32. Tondamanar 33, T~pawewa 34. Unichchai 35. Vmathap~illu

RRI AD

m,m AD MD AD ID ID ID ID ID ID

Tm AD RRI CRl AD m

MECD ID AD ID ID

TRI ID ID m ID

TRI AD ID ID ID ID rn

CHAPTER THREE

Water Resources Development

Sri Lanka has a system of river basins with a high water balance compared to many other countries of the world. If properly utilized, she also has sufficient land resources to sustain the needs of the country in the foreseeablc future. In early 1959 a map titled "Planned River Basin Development of' Sri Lanka," was prepared by the (then) Ministry of Agriculture, Land, irrigation & Power (Fig 3.1). This map, modified from time to time, was to serve as a guide to river basin development, with particular emphasis being placed on irrigation and the development of hydro-power. The assessment of surface water and groundwater resources has been carried out on a systematic basis over the last few decades. All the possible reservoir sites have been selected and investigated. The development of water resources, mainly for irrigation and hydro-power generation, is being taken up in a large-scale to meet the requirements of an increasing population.

For the purpose of water-resources development, Sr i Lanka is divided into four major regions (Fig.3.1), namely:

(a) Mahaweli Project Region, (b) South-East Dry Zone Region, (c) Western Wet Zone Region, (d) North-West Dry Zone Region.

3.1 MAHAWELI PROJECT REGION

The Mahaweli Project Region comprises the administrative districts of' Nuwara Eliya, Kandy, Matale, Badulla, Polonnaruwa, Anuradhapura, Vavuniya and the Uda Walawe Reservoir Project Area. It covers a gross land area of around 25500 sq.km, which is about 38% of the total land area of Sri Lanka. It has been estimated that the annual long-term average discharge of Mahaweli into the sea from a catchment area of 10448 sq km is 11016 million my This volume is about 21% of the total discharge of all river basins of Sri Lanka. The Mahaweli has its source in four small streams, namely, the Dambagastalawa Oya in the Arnbewela hills, the Agra Oya in Horton Plains, the Nanu Oya in Pidurutalagala, and the Dik Oya in Abbotsleigh and Marlborough Estatcs. The first three streams converge to form the Kotmale Oya at an elevation of' about 2400 m M.S.L. The Kotmale Oya-Dik Oya confluence a t Mahawila Ileal. Ulaparle to form the Mahaweli Ganga proper.

PALlTHA MANCHANAYAKE & C. M. MADDUMA BANDAIL4

Figure 3.1: Water resources development in SI-i Lanlia.

A team from the Food and Agriculture Organization (FAO) under the United Nations Development Programme (UNDP), in collaboration with the counterpart officers of Sri Lanka, prepared the Master Plan for the development of the water resources of the Mahaweli Ganga Basin and adjacent areas during the period 1965 to 1968. According to prices prevalent in 1968, the estimated cost of the entire project was in the region of Rs. 6700 million. The plan proposed to harness 5800 million m3 of the annual flow of the Mahaweli Ganga for agricul-

w

tural development of an area of around 364000 ha in the dry zone of the island. Of this extent, nearly 100,000 ha were already irrigated by nearby tanks and reservoirs but were deficient in water supplies to sustain cultivation in both Maha and Yala seasons, and the remaining 264000 ha would be entirely new lands with some being under rainfed cropping. The Mahaweli Master Plan also envisaged the installation of hydro-power plants with a total capacity of over 500 MW for the production of 2600 million kWH of energy annually.

The construction of reservoirs such as Victoria and Randenigala along the parent Mahaweli Ganga, and Kotmale reservoir along the Kotmale Oya, were envisaged to provide hydro-power as well as to act as flood-mitigation reservoirs, particularly in the Gampola-Peradeniya reach of the Mahaweli Ganga, and also in the Manampitiya-Kandakadu area in the lower reaches of the river. Flood control was one of the main objectives of this multi-purpose project, in addition to irrigation and hydro-power generation.

The plan included the construction of several large dams on the main river and its tributaries, a barrage a t Polgolla for diversion ofwater to the North- Central Province, a new anicut a t Minipe, a number of power houses for power generation, the water-conveyance channel systems, the provision of irrigation facilities, the downstream infra-structural development and the settlement of people. It would also augment a number of already existingreservoirs and would enhance systematic regulation to these diversions from Mahaweli. The imple- mentation period of the plan was expected to be aroun'd 30 years.

The first phase of the development of the Mahaweli Project commenced with the construction of the diversion barrage a t Polgolla in 1976. The diverted water from Polgolla is taken along a 8.06 km long, virtually unlined tunnel of diameter 5.95 m, to the power house a t Ukuwela generating 40 MW of hydro power. The diversion capacity of the tunnel was limited to 56.7, m3/s (or 2000 cusecs). The Sudu Ganga river-training works included stream widening and bank protection a t some places in order to accommodate the enhanced river discharges from the Ukuwela power houses.

46 PALITHA MANCWANAYAKE & C.M. MADDUMA BANDARA

The Bowatenna complex consists of a 30.5 m-high dam of length 235 m. It is a concrete gravity-type dain with a gated spillway of 6 radial gates, each 9.75 m (32 ft) wide and 11.3 m (37 ft) high. The Bowatenna reservoir has two tunnels, one for irrigation releases with a design capacity of 28.3 m3/s (1000 cusecs), and the other for power releases, which generates 40 MW of hydropower. The irrigation releases are being conveyed to the 'H' area, namely, the Dambulu Oya and the Kandalama and Huruluwewa reservoirs. The releases to the Dambulu Oya reservoir are subsequently sent down to the Kalawewa reservoir. The Kalawewa has about 23800 ha ofnet irrigation area under its command, ofwhich Dambulu Oya has 2100 ha, Kandalama 4900 ha and Huruluwewa 4300 ha. Beyond Kalawewa reservoir, it also supplies water to the city tanks of Anuradhapura, namely the system 'IH', which comprises the irrigable areas under the Nachchaduwa, Nuwarawewa,Tissawewa and Basawakkulama. Also, the domestic and municipal supplies to the city of Anuradhapura arc being drawn from Nuwarawewa and Tissawewa. The Kalawewa also feeds the Rajangane reservoir, created by damming the parent river Kala Oya, which presently takes the spill waters and the return flows from some parts of the Kalawewa irrigable area (Fig.3.2).

In 1978, the Government of Sri Lanka launched the "Accelerated Mahaweli Development Programme" in which a number of selected reservoirs were taken up and construction undertaken simultaneously with assistance from a number of foreign countries i.e., KotmaIe Project with Swedish aid, Maduru Oya with Canadian aid, Victoria Reservoir with British aid, and Randenigala Reservoir with German aid. The major project components of the "Accelerated Mahaweli Development Programme" (Fig. 3.3) are listed in Table 3 ..I.

TABLE 3.1: Major Components of the Accelerated Mahaweli Project and their Dates of Completion.

Name of Component Completion/Impounding of Reservoir

1. Ulhitiya Reservoir 2. Ratkinda Reservoir 3. Minipe New Anicut/RB Canal 4, Victoria Reservoir 5. Maduru Oya Reservoir 6. Kotmale Reservoir 7, Randenigala Reservoir 8. System B-RB Canal 9. System C-Phase 1-4

July 1982 April 1983 April1983 April 1984 October 1982 November 1982 March 1986 October 1984 (Phase 1) September1985 (Phase 11)

WATER RESOUIZCES OF SRl LAhUC.4

SCHEMATIC DIPGRAM

- DNII)I(QIYW# ImIaATlOW SUYL

--D(VC~IOIIU**L

rar, STATrm

--C C L W U m U l I Q

Figure 3.3: Mahaweli water reso\l,cvs managvment project - Macro system-Mahaweli Ganga. (Source: Ref' 551)

WATER RESOURCES OF SRI LANK4 49

The Victoria Project envisaged the construction of a double-curvature arch dam 118 m high, and a 5.8 km-long tunnel leading to the power station, which generates 210 MW of hydropower. I t would have nominal firm energy of 626 GWH per year, The rated head is 190 m. The active storage of the reservoir is 688 million m3. -

The Kotmale Project consists of a rockfill-type dam 87 m high and 600 m long a t the top of the embankment. The active storage of the reservoir is 152 mcm. A noteworthy feature of this project is the underground power station which has been carved out of Atabage rock. It is the first underground power station constructed in Sri Lanka. The water to the power house is carried by a horse-shoe shaped, concrete-lined, low-pressure tunnel, 6 meters in diameter and 6560 m in length. Its installed capacity is 134 MW,.and it would have a nominal firm energy of 310 GWH per year, and a rated head of 210 m. Kotmalc, being a rockfill dam, has the provision of being raised to higher levels subse- quently.

Maduru Oya has a 43m high rockfill dam, and its reservoir has an active storage of 478 million m3. I t is intended to increase its capacity by another 131 million m%y raising the spill level by an additional 2 m. The reservoir would provide irrigation facilities to about 48000 ha of new land and 3750 ha of already developed lands.

The Randenigala dam is 94 m in height and 485 m in length, and is made of earth and rockfill. It has an active storage of 565 million m;'. The water impounded is conveyed to the power house by an intake structure and a steel- lined tunnel of 270 m in length and 6.2 m in diameter. The power house immediately below the dam has an installed capacity of 122 MW, with nominal firm energy of 428 GWH per year. The rated head is 78 m. The gated spillway on the right flank of the dam has a maximum discharge capacity of 8085 cusecs with 3 radial gates, 16.7 m wide by 15 m high. The outflow from the gates is carried in a 62.1 m wide and 220 m long chute, with a flip bucket at the downstream end to throw the discharge away from the permanent works.

Rantambe dam construction was completed in early 1990 and is an essential link in the Randenigala complex for balancing the outflow ofRandenigala and assuring a uniform regulated flow to Minipe for irrigation purposes. It is a 43 m - high dam, with a central spillway having four radial gates, 16 m wide by 16.4 m high, and a 49 MW power station a t the toe of the dam.

The new Minipe anicut diverts the flow of Mahaweli to about 6200 hectares on the Left Bank (System E) and to about 61000 hectares on the Right Bank (System C and B) under the Ulhitiya-Ratkinda and Maduru-Oya Reservoirs (Fig.3.4).

P U Z T H A MANCHANAYAKE & C.M. MADDUMA BANDARA

WATER RESOURCES OF SRI LrWKA 51

The Amban Ganga, beyond Bowatenna, feeds Elahera Anicut, which caters for System 'G' of about 5400 ha. As there are no reservoirs in Systcrn G, the releases of Bowatenna are arranged to have a run of the Elahera-Minneriya- Yoda-Ela (EMYE) a t all times. I t is generally difficult to feed a run of the river system because of its lack of storage, to meet irrigation demand during long periods. The Minneriya Reservoir feeds the Kantale and Vendrasan Reservoirs by means of Minneriya-Kantale-Yoda-Ela (MKYE), and the Kaudulla Reservoir, in addition to its own irrigable command. The irrigable area under Minneriya, Giritale, Kaudulla, Kantale and Vendrasan reservoirs is referred to as System 'Dl' which covers about 25700 ha. The waters of the Amban Ganga are directed a t Angamedilla to feed the Parakrama Samudra by the Angamedilla Yoda Ela. The irrigable area under the Parakrama Samudra amounts to 10100 hectares, and it is referred to as Mahaweli System D2. (Fig. 3.5)

Efficient and effective water management for both irrigation and hydro power is vital for the successful implementation of the entire Mahaweli Development Programme. With this objective in view, a policy-making body designated as the Water Management Panel, has been constituted. To service the panel, the Water Management Secretariat of Mahaweli Authority was established. The principal function of the Water Management Secretariat is to tender advice to the Water Management Panel in regard to policy decisions and to prepare overall plans for the optimum utilization of the water resources in the Mahaweli Basin both for agricultural production and generation ofhydro power-.

3.2 SOUTH-EAST DRY ZONE REGION

The area coming under the South-East Dry Zone comprises the Districts of Moneragala, Batticaloa and Hambantota. It has nearly 15200 sq km, which is around 23% of the land area of Sri Lanka. But it has a population of only 1.4 million, which is about 9.5% of the total population of the island. A large extent in this South-East Dry Zone is under forest and wild life reserves, namely, the Yala Wild Life Sanctuary, the Kumana Bird Sanctuary, and the Lahugala- Arnparai Elephant Corridor. The major river basins in this region are the Walawe Ganga, Menik Ganga, Kirindi Oya, Kumbukkan Oya, Heda Oya, Gal Oya, Mundeni and Wila Oya.

In the South-East Dry Zone, the river which has the highest run-off is the Walawe, with an annual average run-off of 2200 million m3. The Uda Walawe reservoir has been constructed by damming the main Walawe Ganga, and it has a total capacity of 268 million m". I t has a development area of around 32000 ha and a power plant of installed capacity of 6 MW. The Chandrika Wewa of' 29 million cubic meters capacity has been formed by damming across the Hulanda

PUITEIA MANCIIANAYAKE & C.M. A4ADDURIA BANDAFU

The Gal Oya basin was one of the earliest to havc been dc\~cloped ill recent times. The Senanayake Samudra, which was built durjlig 1949-52 by constructing a n earthen dam across the Gal Oya at a narrow gap in thc valley of the Inginiyagala hills, has a storage of 950 million m". This is considered to be the biggest water mass for any reservoir in Sri Lanka and it irrigates around 49000 h a on both i ts banks; it has a power plant of installed capacity of 10 MW.

The Navakiri Ara reservoir of 52 million m" caters for 6,000 ha; thc Unnichchai reservoir of 47 million mveeds 3700 ha in the Magalawatuwan AI-a basin, and the Rugam Tank of 23 million m" irrigates 3250 ha. The Illundcni Aru basin has a higher annual run-off figure, and feasibility studies have already been done for the Rarnbukkan Oya reservoir in the higher reaches ol'Milndcni Aru. Two other reservoirs have been proposed in the same basin, in addition to the Rambukkan Oya reservoir. They are the Maha Oya reservoir across the Maha Oya and the Gallodai Aru reservoir across the Gallodai Aru, which subsequently form the Mundeni Aru further down in the basin.

3.3 WESTERN WET ZONE REGION

This region comprises the Districts of Colombo, Gampaha, Kal~itara, Kcgalle, Ratnapura, Galle and Matnra. The total extent of this area a~noilnts to 11,480 km" which is about 17.7% of the total land area of Sri Lanka. However as much as 46(k of'the country's population lives in these districts. The ~nqjor river basins in this region arc the Nilwala Ganga, Gin Ganga, Iialu Gslnga, Kelani Ganga and the Attanagalu Oya.

The 72 km long Nilwala Ganga drains through a n area of 971km" I t has an annual runoff of 1379 million mJ. An approximate area of about 60% of the Nilwala Ganga basin is cultivated predominantly with tea, rubber, coconut and rice. Rice covers a n area of about 16200 ha. Nearly half of this area, found in the lower reaches of the Nilwala basin, is subject to recurrent flooding, and as a remedial measure the lr~igation Department started the Nilwala Ganga Flood P1.otection Scheme with assistance from the French Government. The effective- ness of this scheme is in doubt since i t has created other probienls which have affected thc existing paddy areas.

The Gin Ganga, which is about 112 km long, origiilates from Abbey Rock at around 1300 m above mean sea level, and passes through Udugama and Baddegama areas, and flows into the sea at Gintota. It has a catchment area of 932 km2 and a n annual runoff of about 2178 million m" The basin is fairly well developed, the upper hill country region being planted with tea and rubber and the lower areas with coconut and cinnamon plantations.

WATER RESOURCES OF SRI LANKA 55

The paddy areas, amounting to 14200 ha are in pockets all along the rivcr where nearly half this amount is situated in the lowland which is subjected to recurrent flood damage. The Irrigation Department launched the Gin Ganga Flood Protection Project with the aid of the Chinese Government. Construction of levees and flood-protection bunds along the Gin Ganga, beyond Baddegama and the installation of pump houses were the main proposals that were taken up.

The Bentota Ganga has an annual yield of 1247 million m3 and drains through an area of 629 km2. I t originates in a plateau above Pitigala, a t an altitude of about 300 m and runs through a lowland course and falls into the sea a t Bentota, near Alutgama. The upper reaches of the basin are planted with rubber. In the lower reaches, coconut on highland and some paddy cultivation in the lowland can be seen. The frequent inundation by periodic floods imposes hardships on the area and retards agricultural development.

The Kalu Ganga commences from sources in the Central hills a t Sri Pada a t about 2100 meters above mean sea level. Even though it has a drainage area of only 2720 sq. km. and a length of 129 km, it has the highest ratio of the annual run-offto catchment areas, and discharges some 8183 million m3 to the sea. Even though the Mahaweli basin has nearly four times the catchment area ofthe Kalu Ganga, its annual run-off remains a t 8140 million m3. The Kalu Ganga drains through some of the wettest areas of Sri Lanka near Ratnapura, and the average annual rainfall of the catchment amounts to 4064 mm, with more than half' ofit received during the monsoonal months of May and June. The catchment area is developed agriculturally with tea on elevations above 600 m and rubber, coconut and paddy being grown in the lower regions. It has been reported that 14000 ha oftea, 57,000 ha of rubber, 12000 ha of coconut and about 25000 ha of paddy are being grown in the Kalu Ganga basin. Of the 25000 ha of paddy in the basin, more than 50% is located in the area affected by floods. Proposals have been made for the construction of two reservoirs in the Kalu Ganga basin, namely the Ratnapura Reservoir and the Kukule Reservoir. Tshe Ratnapura reservoir has been proposed for flood control and the Kukule dam across Kukule Ganga in the higher reaches of the Kalu Ganga has been proposed for hydro power generation and for possible trans-basin diversions to the South-East dry zone.

The Kelani Ganga also has its source in the central hills near Sri Pada; i t flows through the western part of the island and falls into the sea a t Colombo. It has a catchment area of 2292 km2 and has an annual run-off of 5579 million m3. The Kelani Ganga begins at the confluence of the Kehelgamu Oya and Maskeli Oya, and it is subsequently joined by tributaries such as the Sitawake Ganga, Gurugoda Oya and Wey Oya. The characteristic feature of all these tributaries is their steep gradient of around 38 m per km of the stream. The hydro power potential in this river basin up to the confluence of the two major

56 PALITHA MANCHANAYAKE & C.M. AtAl~IlLJMA BANDiLt7A

streams, uiz., the Kehelgamu Oya, Maskeli Oya has been almost totally exploited. The Moussakelle Reservoir on the Maskeli Oya feeds the Canyoil Power Station and subsequently, through the Canyon Pond, the Ncw Laxapana Power Station. The Castlereigh Reservoir on the Kehelgamu Oya feeds the Wimalasurendra Power Station and subsequently, through Norton Pond, the Old Laxapana Power Station. The flows of both the Maskeli Oya and the Kehelgamu Oya, after generating power a t New and Old Laxapana Power Stations, respectively, pool up a t the Laxapana Pond, which feeds the Polpitiya Power Station (Fig.3.6). The Wimalasurendra Power Station has an installed capacity of 50 MW and nominal Firm Energy of 104 GWH per year*, at a ratcd head of 227 m. The Old Laxapana Power Station has an illstalled capacity of50 MW, with nominal Firm Energy of 228 GWH per year, at a rated hei~cl of449 rn. The New Laxapana Power Station has an installed capacity of' 100 MW with nominal Firm Energy of 504 GWH per year, a t a rated head of 578 m. The Canyon Power Station has 60 MW of installed capacity 130 GWH per year of nominal Firm Energy, a t a rated head of 204 m. The Polpitiya Power Station has 75 MW installed capacity with 448 GWH per year of nominal Firm Energy, a t a rated head of 259 m.

Preliminary proposals fbr further development in the Kelani basill havc been framed for detention reservoirs, together with a levee system and transbasin canals. These development proposals envisage flood protection, hydro power generation and transbasin diversions of surplus water resources to the north- western sector of the country to command about 62600 ha.

The Attanagalu Oya, which drains an area of 736 km2, has an annual flow of S45 million m3 and can be considered as a typical lowland wet zone catchment, I t does not have any reservoir storage, but allirrigation activities are based on a series of anicuts across the main Attanagalu Oya and its tributaries. The main tributaries of the Attanagalu Oya are the Deyella Oya and the Uruwal Oya. There are anicuts such as Pallewela, Muruthawela, Maha Arnuna, Panugala and Idallawala across.the Diyella Oya, and the Uruwal Oya has anicuts acrossit a t Kinigama, Galwetiya, Bogampitiya and Welikada. Tho main Attanagalu Oya has a series of major anicut schemes such as Morenna, &tawala, Tammita and Kotugoda along the main stream. The total irrigablu area covered by all these anicuts amounts to about 3260 ha.

3.4 NORTH-WEST DRY ZONE REGION

The North-West Dry Zone Region comprises the Districts of Jaffna, Vanni, Puttalam and Kurunegala. The total area of this region is around 16435 km2, which is nearly 25% of the land area of Sri Lanka. Arouizd 19% of'the Island's population resides in this region. The major rivers in the region are the

WATER RESOURCES OF SRI LANKA

Maha Oya, Deduru Oya, Mi Oya, Kala Oya, Moderagam Aru, Illalwathu Oya, Parangi Aru, Pali Aru and Kanagarayan Aru.

The Maha Oya originates in the Ulapane, Alagalla and Aranayake areas and runs for about 125 km before reaching the sea just north of Negombo. I t has an annual run-off of 1485 million m3 from its catchment of 528 km2. The basin is well developed with coconut, rubber and other crops of the wet and interme- diate zones. Some rice cultivation is also found in isolated valleys irrigated by small diversion anicuts, in addition to the major anicut of the Yakabendi Ela Scheme. The Yakabendi Ela anicut is 100 m long and 7 m high, with 2 radial gates of 7.7 m width and 4.9 m height. This major anicut caters for 3200 ha of' double-cropped paddy.

The Deduru Oya has its source in the foothills of Matale and flows through 140 km in the Kurunegala and Chilaw areas and reaches the sea north of Chilaw. I t has a catchment area of 2647 km2 and has an annual run-off of1129 million m" on the average. According to folklore Deduru Oya is noted for i ts flash floods since ancient times. The upper reaches of the Deduru basin, covering about 1490 km2 are situated in the wet zone in Matale, the rest being in thc dry and intermediate zones. The Deduru Oya has two major anicut schemes, namely, the Deduru Oya anicut a t Hiriyala Electorate and the Ridibendi Ela anicut in the Yapahuwa Electorate. The former anicut has about 1005 ha and the latter has 1930 h a of paddy. The Deduru Oya is generally well developed with coconut cultivation, which forms the mainstay of the agricultural activity of the region. I t has four major reservoirs, namely, the Batalagoda, Hakwatuna Oya, Magalle wewa and the Kimbulwana Oya, inits catchment. The Batalagoda Reservoir has 5.97 million m" capacity, and irrigates about 2020 h a and the Hakwatuna, Magallewewa and Kimbulwana have 239.8 million mQapacity, and 1760, 1660 and 480 h a of irrigable area, respectively.

The Mi Oya drains an area of 1533 km2 and has a n annual yield of' 198 million m:'. The major irrigation works in operation include the Mi Oya Diversion Scheme and the TabbowaTank, which has been constructed across the Nanneri Oya, a tributary of Mi Oya. The Irrigation Department recently completed the construction of the new Inginimitiya Reservoi

r

. The Tabbowa Wewa has 9.7 million m-torage, with irrigation facilities for 650 ha. The Inginimitiya Reservoir has a command area of some 2600 ha.

The Kala Oya basin has a number of reservoirs, such as the Kala Wewa, Rajangane, Angamuwa, Kandalama, Dewahuwa and Dambulu Oya, all of which come under the Mahaweli Project Region System 'DI'. I t falls to the sea north of Vanathavillu off Puttalam, traversing the Wilpattu National Park. The drain- age waters from its irrigated areas has significantly enhanced the fresh water inflows into the Puttalam Lagoon.

WATER RESOURCES OF SRI LANILA 59

The Modaragama Aru has its source near Anuradhapura and flows westwards as a dry zone stream. It has a catchment area of 943 km%nd an annual runoff of 169 km? I t has the Mahawilachchiya Wewa and the Moderagam Aru anicut in its basin as the major irrigation schemes. The Mahawilachchiya wewa has a capacity of 40 million km3 and feeds some 1065 ha under its command.

The Malwatu Oya, which passes through Anuradhapura, originates in the Ritigala Hills, and drains an area of 3284 km'. I t has around 566 million m.' of annual runoff: The Malwatu Oya can be considered as one of the earliest to develop river-basin settlements dating back to prehistoric times. There are about 1450 working tanks in this basin, mostly village tanks. The larger reservoirs in the basin include Nachchaduwa, Tissawewa, Nuwarawewa, Basawakkulame, Mahakandarawa, Pavatkulam, Giant's Tank and Iratperiyakulam. Most of these reservoirs had been in operation from the Anuradhapura period in Sri Lankan history. Some of these tanks receive Mahaweli waters which au-ment their normal supplies for irrigation. Among them are: Nachchaduwa, Nuwarawewa, Tissawewa and Basawakkulame. The municipal supplies to the town of Anuradhapura are drawn off mostly from Nuwarawewa. Most of thc major tanks in this basin come under the Mahaweli Projcct Region, while only the tail end of Malwatu Oya comes within the North-West dry zone. Some of the reservoirs in the Malwatu basin such as Mahakanadarawa suffer from serious water shortages resulting from unplanned small tank development activities in their catchment areas.

The Parangi Aru has a-catchment area of 842 km2 and has only 225 million m%f annual runoff. The Pali Aru has a catchment area of 456 km2 and an annual runoff of 112 million m3. The only other river basin which has some significant runoff is the Kanagarayan Aru, with 907 km' and 242 million m.' annual run-off. The Iranamadu Tank with 101 million m3 storage and irrigating about 7500 ha, has been formed by a dam across the Kanagarayan Aru.

3.5 ECONOMIC ASPECTS OF WATER RESOURCES DEVELOPMENT

The term "Water Resources Development" covers a wide field, encom- passing many scientific, engineering and other disciplines such as meteorology, geography, geology, hydrology, hydraulic engineering, foundation engineering, dam engineering, agricultural engineering and agronomy. Besides such a wide interaction of disciplines, varied purposes like irrigation, hydro power genera- tion, domestic and industrial water supply, navigation, fisheries and recreation involve a t least two other disciplines, namely, ecology and economics. As required by existinglegislation, i t is essential to screen every major development project through an Environmental Impact Assessment (EIA).

60 PALJTIIA MANCI-IANAYAKE & C.M. MiLDDUMA BA-VDfLl?A

3.6 SUPPLY AND DEMAND FOR WATER

In Water Resources Development, the water resources planners have the primary task of matching the available supply ofwater with its demand. The sources generating water are more or less natural and are generally characterized by a number of factors described by din'erent componcnts of'the hydrological cycle such as precipitation, interception, evaporation, transpi~a- tion, infiltration, surface runoff, interflow and groundwater flow. Peoplc generally have very little control over rainfall, except for limited attempts of artificial rain-making such as cloud-seeding which a t best provide dubious results. On the other hand, water is in great demand for different human uses, which can be broadly categorised as domestic and municipal, commercial and industrial, irrigation and agricultural, the generation of hydro-power, naviga- tion, recreation and aquaculture. In considering the needs of these varied uses, the demand for water should be evaluated in terms o f :

(a) quantity per unit time (b) quality (c) timing (d) reliability, and (e) spatial location

(a) Qzsantity per unit time: Essentially, domestic and urban supplies are indicated by the number of gallons per day (gpd) used; for a large-scale supply such as for the Colambo Municipality, it is measured as million gallons or million cubic meters per day. The entire population of a town or municipal area depends on a water supply system, and being a very essential commodity watcr has to be contiiiuously provided irrespective of costs, except under veiy special conditions such as in the case of severe droughts or civil disturbances. Even ii~dustrial and commercial establishments depend on a constant supply measured as q~~antiky per unit time. This amount lias to be catered for by the system for a very large percentage of time, particularly for water-based industrial and commc~,cial ventures if they are to be efficient and productive. Even in irrigation reservoirs, if there is a certain amount of acreage that has beencultivated, then the reservoir system has to cater for that acreage in order to avoid cultivation losses.

(b) Qrsality: Quality is characterized by different specifications, for instance: it s h u l d not have dissolved solids and suspended sediments above certain specid fied levels expressed as parts per million (ppm) and not above a certain amount of Biological Oxygen Demand (BOD). For domestic supply the population should be supplied with potable water of a suitable quality for human co~isumption.

WATER RESOURCES OF SRI LAN- 6'1

(c) Timing: As time goes on, the demand also changes. An irrigation area, for exanxple, needs water only when there are no rains; if there are adequatexai~ls to meet wvp-water requirements, no irrigation issues are needed. Again, there is less demand for water during the rainy season as against the dry season. The system should be capable of meeting changing demands a t the times when they are needed. The demand for domestic and industrial uses also changes with time. During the day, peak demand occurs during the mornings; minimum demands are mainly towards midnight when there is less activity.

(d) Reliability: The demand for water could also be characterized by its l-eliability. DifTerent users would .have different demands for water with different reliabilities. Domestic and municipal supplies should have a very higl-~ reliability, a s the people of a city depend on i t entirely for their domestic and consumptioa uscs. But for an industry which takes water from a nearby stream, a relatively lesser reliability can be tolerated.

(e) Spatial Location: The demand for water can also be characterized by the spatial location. This means that the water is needed a t a particular location far removed from its source. I t is needed in towns and cities where the population concentrations are found. The water-supply system for the city of Colombo is a t the Labugama and Kalatuwewaxeservoirs, which is about 30 km away. I t would be the same tbr an irrigation reservoir where the irrigation area would be 10 to 20 km away from the head works, from which a system of canals conveys the water. Another example of spatial location is provided by alift-irrigation project, where the water is available at a lower elevation physically, whereas the demand for it is at higher elevations to which water has to be lifted for use in cultivation.

3.7 WATERRESOURCESYSTEMS

The law of supply and demand holds true in the case of water resources projects as well. In an irrigation project, the demand for irrigation waters would be very minimal during the rainy periods but a large quantity of water would be required during the dry spells. Thus, the water resources planners have a difficult task to perform in trying to match the natural supply ofwatcr with the demand, where it is needed in diEerent forms such as quantity per unit time, quality, timing and spatial location. In perfolming this task, the engineers make use of water-resource systems comprising the following:

(a) reservoirs, (b) aqueducts, canals, tunnels and penstocks, (c) water-treatment plants, (d) pumping stations.

62 PALITHA MANCHANAYAICE d3 C.M. AllWDUMA BrUVVARA

(a) Reservoirs: The purpose of a reservoir is to store the run of'the river ilows for issue during periods of dry weather flow. In other words, the rcservoil- acts a s a buffer resulting in changing the pattern of stream flow. A reservoir would increase the possibility of redistributing the water with time in a much more orderly and equitable manner, no matter whether it serves a n irrigation area, or a human population in a village or the township, or a hydro power generation scheme.

(b) Aqrtedrrcts, Canals, Tztnnels and Penstocks: These are used in water-resource systems to transfer water from one location to another. As pointed out earlier, the demand fbr water is not often a t the places where the water is available, but a t places away from the source. For example, there is not a s much demand Ibl. water a t Labugama as in the city of Colombo, and so i t has to bc co~iveycd by pipes. Likewise, i n power generation, the water needs to be supplied a t the power house under a certain head of water, and this is done by tunnels and penstoclts. I n the case of irrigation reservoirs, the water is pooled up and collected a t the reservoir upstream, and the water conveyed to the command area by canals several kilometers away from the source.

(c) Water-Treatment Plants: Water-treatment plants are used in water resoul.cc! systems to improve the quality of water to acceptable standards. There is n 1.c;11 demand in towns and cities for good quality water. The water quality should bcx up to thc prescribed tolerance limits for human consumption.

(dl Pz~mnping Stations: Pumping stations are being used to inci.ease the potctn ti :11 energy of water. By pumpingup to a storage tank, the water is shifted in spatial location from lower levels to higher elevations. Generally, in water-supply schemes, the water is pumped from the rive; to the water tank which is a t a much higher elevation and location so tha t it could feed the entire city or the town under gravity flow. This method of pumping is also used in lift-irrigation schemes where the irrigable land is situated a t a much higher clevatiol~ t11al1 the waterway.

The criteria involved in water allocation is largely a matter ol'econoinic feasibility. I11 some instances, economic feasibility has to be gi vcn lower priority where it is essential tha t good quality water has to be provided to u specific area. A case in point is the allocation of water to the cities such a s Colombo or Kalzdy.

3.8 ECONOMIC FEASIBILITY

Generally i n the planning of small-scale irrigation projects, it was the universal practice about 40 years ago to evaluate their economic viability on tlle basis of pro-rata costs. In this method, the total cost of the project is cstimatccl

WATEIZ RESOURCES OF SRZ WVKA t;:j

and a ratio of cost per acre of cultivation is considered as a criterion of'evaluation. The benefit-cost ratio of a project was however, often overlooked when i t was felt that the irrigation projects were immensely beneficial and were absolutely essential. In this connection, it may be of interest to speculate on the cost of massive, miles-long bands of ear th work involved in ancient dams. (Manchaizayake, 1987)

In the UilitedStates, the rules enumeratedin the firstofYicia1 publication, "Proposed practices for economic alzalysis of river basin projects"(m ore popularly known as the Wreel~ book") by the U.S. Inter-Agency River Basin Committee had come into effect only in 1950. The objective was to set down the standard procedures that were to be adopted by all agencies. With the introduction oi'tlw "Green book", the benefiucost ratios came into vogue, where tlze benefits ofthe project and its cost were evaluated and a ratio established. This ratio, referred to as the benefithost ratio, indicates the economic worth of the project, and it should be higher thanunity for i t to be considered for implementation. In the case of benefits, only the primary benefits of an irrigation reservoir, such as the intended agricultural produce, are considered for evaluation. Tllc intangibles or secondary benefits, such as inland fishing, growth of secondary industries, solving of unemployment problems in the area to some extent by menus offarm labour and other means and the increase in land values of the arca are gener-ally given less prominence. In the case of multi-purpose reservoirs, the benefits that accrue by hydro power generation and the savings resulting from flood-dantagc protection of the recurrent floods that took place prior to the construction of the reservoir are considered as primary benefits and are taken into consideration for evaluation. The cost stream comprises the cost of construction of headworks, namely, the dam, spillways, sluices, the water conveyance systems, including downstream anicuts, barrages, level crossings, aqueducts, siphons, and the channel outlets. I t also includes the provision of irrigation facilities, the operation and maiiztcnance cost of'the system, tlze replaceme~lt cost of' somc components such as the spillway and sluice gates over a certain period and thc recurrent cultivation cost in each season.

As most of the costs are in the construction period ofthe project, and t l ~ c benefits will be spread over the period of operation, both the cost and benefits streams need to be brought to a common time base, and the benefitlcost ratios evaluated thereafter. This is usually done either by the "Present Worth" or the * "Equivalent Annual Values." In defining the benefithost ratio, different metli- ods could be adopted, such as taking the opportunity costs/slzadow prices into account, and also the guaranteed pricelmarlret prices. The higher the benefit1 cost ratio, the higher would be the economic worth of the project. 111 t lx casc of opportunity costs, one may be able to give dif'f'irent weightages to diSfircnl components, such as the scarce fbreign exchange needed for the project and the surplus unemployed unskilled labour.

64 PALZTHA MANCHANAYAKE & C.M. MAD1)UMA BANDfUCA

The Internal Rate of Return is one other method of assessing the economic worth of a project. This could be referred to as the interest rate a t which the total present worth of benefits equals the total present worth of costs over its economic life span. In other words, it can be referred to as the interest rate at which a loan could be taken to implement the scheme so that the bcnefitlcost ratio is equal to unity.

The "Net Present Value" is another measure of the wostl~ of a project which is thc difference between the total present benefits and the total present costs of the project.

For economic comparison of competing water resources projects, irrespec- tive of the method used, namely, the Benefit/Cost ratio, the Internal Rate of Return or the "Net Present Value", the principal criterion involved is the national economic efficiency objective. In other words, which of an alternative set of projects would give the best economic returns to the nation is the prime concern. The new trend in water-resources development is to go for the Multi- Objective Planning Approach, which is being practised in the United States and many other countries.

3.9 MULTI-OBJECTIVE PLANNING APPROACH

The Special Task Force of the United States Water Resources Council introduced the basic principles of the Multi-Objective Planning Approach to Water and Land Resources. In this approach, the purpose of water and land resources planning should reflect the society's preferences for attainment of the followi~lg objectives:

(1) to enhance national economic development by increasing the value of the nation's output of goods and services. and maximising the naticlnal economic efficiency;

(2) to enhance the quality of the environment by management, conser- vation, preservation, creation, restoration of improvement of the quality of certain natural and cultural resources and ecological systems;

(3) to enhance the social well-being by dispersion ofpopulation, increasing employment opportunities, and equitable distribution ofreal income, by contrib- uting to the security of life and health, by providing educational, cultural and recreational opportunities.

WATER RESOURCES OF SRZ LANKA 65

(4) to enhance regional development through increase in a region's income, increase in employment and increase in its economic base, environment, social well-being and other specified components of regional objectives. (Manchanayake 1985)

The applicability of Multi-Objective Planning Approach would be of relevance to the developing countries of the world like Sri Lanka, where the project preferences or the selections for implementation would be done not only by the national economic efficiency objective but by taking the environment, social well-being and regional objectives also into consideration. As countries in the Third World need a considerable amount of development activity, the general upliftment of living conditions, good infra-structural facilities, the availability of basic human needs such as hospital facilities, shopping centres, market places, schools, playgrounds, post offices and other amenities, this approach would be very appropriate. In the Sri Lankan context, some areas where water-resources development has much potential in terms ofthe above objectives, include among others, the Lower Uva, the Bintenna Pattu ofMoneragala and Ampara Districts, the Anamaduwa areas and many others. The social well-being of the population, the regional development ofthe areas and the formation of secondary industries such as inland fishing being introduced to the area once the reservoirs are constructcd, would be some of the vital factors to be considered under the Multi- Objective Planning approach for projects in those localities. The improvement of the quality of environment such as the scenery and ecosystems and the provision ofrecreational facilities to the society in addition to its normal national economic efficiency objective, would promote such projects in these areas.

CHAPTER FOUR

Utilization of Water Resources

4.1 PUBLIC WATER SUPPLY

At the last census (19811, 21.5 % of the population in Sri Lanka was urban and the balance, including the plantation sector, was rural. About 70% of the urban population in Sri Lanka is served with pipe-borne water supplies. However, in the rural areas only about 15% enjoy this facility. This situation has improved in recent years through rural development projects. However, the majority of the rural people obtain their drinking water mostly from private wells andin somc areas from community wells. The quality ofwater used in rnvst areas is doubthl as the wells are not often protected against contamination. Many people still use water from surface water bodies such as reservoirs, canals, streams and lakes where the water is often contaminated and therefore not suitable for human consumption. The high incidence of bowel diseases which accounts for a large proportion of hospital admissions is an indication of this problem.

The responsibility ofutilizing surface and ground water through water- supply schemes, lies with the National Water-Supply & Drainage Boa]-ci (NWSDB). I t has already established a number of water supply schemes Ibr urban as well as for rural areas of Sri Lanka. The Government of Sri Lanka, wi tll the assistance of the UnitedNai;ionsDevelopment Programme (UNDP), laullcl~cd a project for praviding safe drinking water to all people in Sri Lanka by the year 1995. The targets that have been set out were to cover 100% of the urban water- supplies and 50% of the rural water supplies before the end of the century. The estimated expenditure for this project is nearly a billion US dollars. Figure 4.1 is a map of Sri Lanka showing water-supply schemes that were under construc- tion and coming under the above project.

A water-supply scheme is needed by the public, mainly for domestic uses such as drinking, culinary uses, washing, bathing, laundering and for watering plants and lawns. To provide for these varying needs, water must be adeq~~atc in quantity and satisfactory in quality, readily available to the user, relatively cheap and easily disposed of after it has served its purpose. Another important public use of water is for fire extinction.

The demand for domestic water is bound to increase with the increase in population, rapidindustrialization and rising standards of living. The minimum requirement of water for an individual would depend on his standing in society,

Figure 4.1: Si-i Lanka domestic water.

WATER RESOURCES OF SRI LANKA 69

water use habits and on the type of supply available to him. Water in its natural state is still available free of charge a t the source. Pipe-borne treated water on tap is invariably a high-priced commodity.

The engineering works often involved in water-supply schemes arc water conveyance, water treatment and waste-water disposal systems. Thc basic considerations that govern the design of a water supply scheme would be the area and population that are to be served, the design period, per capita rate of consumption and the other needs for water in the service area. Normally, a water-supply scheme is designed to meet the requirements for a period of 20 years. However, certain project components such as electric motors, pumps and water-treatment units are designed for shorter periods of 10-15 years. In order to estimate the population to be served during the design period, it is necessary to assume a suitable rate of growth. Where service connections are provided, the per capita demand is generally taken as 40 gallons per day, and for supply through stand posts it is taken as 10 gallons per day. The actual use 11owevc.1. depends on the above factors as well as on wastage which is very high in SI-i Lanka.

The water supply to the Greater Colombo Development Area would be an improvement to the existing system, where the impounding reservoirs of Labugama and Kalatuwawa would be incorporated with the Kelani river to supply a total of 130 million gallons per day. Ofthis amount, 100 million gallons per day would be from the Kelani ganga and 30 million gallons per day would be from the two reservoirs. These are some of the requirements anticipated by the year 2000.

With regard to rural water-supply schemes too, the provision of' safe drinking water has been the main goal. With this objective, many rural piped water-supply projects have been established. But it should also be realized that with the increasing costs of operation and maintenance3 such projects have not been very feasible. As such, the new trend has been to go for deep-well groundwater as the source is generally safe and serves the same purpose as that of a piped water-supply scheme to the rural community. The main advantage of this facility is the low operation and maintenance costs. Groundwater exploita- tion has now been developed to the extent that the demand for tube wells or deep wells is apparently replacing the earlier, more specific, demand for pipe-borne water-supply systems, in most areas.

4.2 INDUSTRIAL WATER SUPPLY AND DISPOSAL OF EFFLUENTS

Industrial development in the island has increased during the recent past with the opening up of several new industrial areas. The industrial water

70 PALITHA MANCHANAYAKE & C.M. MAUUUMA BMTDM?A

supply has not, however, caused major problems so far, as most of the industries which require large amounts of water have been located close to surface water or groundwater sources. However, pollution of water bodies by the discharge of effluents is a growing problem. The Free Trade Zone Industrial Complex in the Greater Colombo Development Area has been provided with tube wells yielding over half a million gallons of water per day, through a network of tube wells tapping local groundwater bodies, in addition to whatever surface water sources available.

Some of the industrial complexes that use surface-water sources from waterways, include the Tyre Corporation (Kelaniya), Steel Corporation (Oruwala ), Leather Corporation (Mattakkuliya) and Pugoda Textiles (Pugoda), all depend- ent on the Kelani Ganga. Similarly, Thcllhiriya Textiles (Alawwa) depends on the Maha Oya, Plywoods Corporation and Ruhunu Cement on Gin Ganga and the Associated Motorways and Tyres (Kalutara) on the Kalu Ganga.

The industrial waste waters contain numerous substances that could be harmful to the environment when untreated and discharged into the streams. The water users downstream who use these polluted waters are exposed to their toxic effects. Thus, strict laws are now being enforced by the Government of Sri Lanka to prevent any random disposal of effluents from factories and other sources without treatment up to required standards of purity. Regulations under the National Environmental Act (Nos. 47 of 1980 & 56 of 1988) specify the general standards and tolerance limits for discharge of ef'fluents into inland surface waters and into marine coastal areas.

The nature of the polluting material would depend upon the type of industry and the different processes used by it. Their polluting effects are generally categorized as toxic wastes (the wastes which are poisonous to living organisms or contribute to the oxygen depletion of the receiving waters) and non- toxic wastes. 111 addition to effects on human health and well-being, there exist, in an unpolluted water body, a complex community, including plants, animals and micro-organisms, which make these water bodies their habitats. Various physical and chemical properties and characteristics of streams such as the speed of water, bed slope, nature of the river bed, temperature and the pH value govern their distribution, When waste material is introduced into this system, it affects the quality of the water that existed before, and therefore, any substance that upsets the natural balance in the environment could be referred to as a pollutant. The usage of terms such as 'pollutants', 'toxic chemicals'and 'wastes' are more fully and precisely defined under the interpretations of the National Environmental Act.

WATER RESOURCES OF SRI WVKA 71

When organicmatteris releasedinto the streamsit increases the food for the micro-orgailisms, and finally they break down into carbon dioxide, water and the mineral salts. But, what really happens would be that, there is such ail increase in their activity that the rate of oxygen intake may well exceed the rate of regeneration in the stream, thereby making the dissolved oxygen lcvel in the stream to decrease. It has been universally accepted that the dcpletjo~~ of this dissolved oxygen level in any water body below 4 mg/l is harmful to aquatic life. However, industries have a general tendency to ignore these problems of pollution because of the additional costs involved in purifying the effluents, without any monetary returns. The government has, therefore, to ensure that the industrialists adhere to the requirement of the laws in relation to thc discharge of toxic waters into inland or coastal water bodies,

Despite governmental controls, there is increasing evidence of urban and industrial pollution in several areas of the country. In Colombo, the quality of the waters of the Beira Lake began to deterio

r

ate with urban developnlc~lt in the last century. Today, Beira Lake is a good example of eutrophication whe

r

e the 'greening'is due to algal blooms caused by the blue green alga Microcyst. The purification of Beira Lake today has become a technical challenge of high cost (NARESA, 1991).

Similar examples are found in the Kandy Lake where the deterioration of the water quality has affected its aquatic fauna, while the Meda Ela, issui~lg from it has become an eye-sore with its black water and a source of' ui-ban air pollution. Along the coast-line where the expansion of the tourist industry necessitated the development of large hotel complexes, beach pollution 1x1s assumed serious proportions.

4.3 USE OF WATZR FOR IRRIGATION

Systems of Irrigation

The topography of Sri Lanka and the prevailing monsoonal pattern havc encouraged the development of' irrigated agriculture, These factors also deter.- mine the different irrigation systems that are appropriate to various areas of'tbc country. Sue11 irrigationis mainly of the flood irrigation type. Furrow irrigation plays a major role. There is hardly any sprinkler irrigation in Sri Lanka. l'lze most common system in the wet zone of Sri Lanka is the flood irrigated paddy. Because the wet zone rivers and streams are generally perennial and the raiilfall is somewhat evenly distributed, this paddy cultivation is mostly rain-fed, with a few anicut schemes operating. In the dry zone however, the stream flows are not perennial, and the rains are generally during the north-east monsoonal period. Thus irrigation water during the south-west monsoon or theYala period

7.2 PM.7 THA MNVCIIINVAYAKLZ & C. M . ILIADL)IJI1lAA UANr~ARA

is essential. In the dry zone, paddy is cultivated by flood irrigation and otlwr crops, such a s chillies, onions, soya beans and cowpea are being grown under furrow irrigation.

Irrigation water can be conveyed to the cultivable land by several methods, namely, by flood, furrow,sprinkler or drip systems. In flood irrigation, the water is made to flood the land and to cover the surface of the soil as a continuous sheet. Theoretically, the water should be a t every point in the field .just long e n o ~ ~ g h to recharge the root zone. Ilk practice this ob.jective is not achieved. Some parts ofthe field may receive too much water, while ot11el.s receive inadequate or barely adequate supply, variation bcing iniluenccd by particular land form. Drainage is equally important as is irrigation. Flood irrigation is generally applied to flatter areas, where each field is divided into paddy plots. The water is issued from the field canals to each field a t the highest levels and flows slowly to the lower levels before being drained into channels.

In furrow-irllgation, water is applied in the furrows between the l.ows of plants. As water runs down the rows, part of it filters into the soil t o recharge the soil moisture. To accomplish this adequately, a considerable amount ol lateral moisture movement in the soil is necessitatedunless the furrtrws arc close to each other. As the moisture moves laterally and upwards, soil salts move with the water and there is a tendency to accumulate in the bed; this could bc injurious to plant growth a t times. Furrow irrigation is generally used on slopes of less than 4 % for the irrigation of dry food crops. Usually water is issued from a field canal to a furrow which runs over a distance of 100 to 200 m at a slight gradient towards the drainage canal. Furrow irrigation is characterized by relatively higher labour cost for maintenance and operation than flood irriga- tion, and it requires intensive land preparation.

The sprinkler irrigation systems, as practised in system B of'the Macluru Oya project, can be designed in different ways. They may be permanent installations with buried main lateral lines, semi-permanent installatiol~s with fixed main lines and portable laterals, and fully portable systems with portablc main lines and laterals. Ili these systems, water is delivered through a main line, from the source of supply to the lateral line. It is discharged above the crop of soil surface through sprinkler heads on riser pipes attached to the laterals, Each sprinkler head applies water to a circular area, the diameter ofwhichis governed by the nozzle size and the pressure. The sprinkler is generally applied to land with slopes greater than 4%. It may also be used for areas beyond the command of gravity water or on irregular topography. Sprinkler systems that are propel-ly designed, installed and operated have many advantages. Soil erosion call be controlled and efficient irrigation is possible on land which is too steep for otlicl.

WATER RESOURCES OF SRI LcWKA 73

methods. Uniform application of water is possible on all kinds of soil. On sandy soils that have high intake rates, sprinkler irrigation distributes water more uniformly than does any other method. Water could be conserved and more land could be irrigated with a smaller quantity of water. Drainage problems can be minimized.

Drip irrigation is another piped water-supply system where the water drips near the plant roots. I t is a costly method of irrigation, but useful in controlling amounts of water where there is a severe scarcjt.3-. There are one or two places in Sri Lanka where drip irrigation is tried out. One such place is at the Agricultural Research Station a t Eluwankulam, north cf Puttalam, where citrus cultivation is drip irrigated, and the other is in system B of'the Maduru Oya Project.

In some irrigation schemes in the north such as in Muttaiyan Kattu Kulam, Pavatkulam, Vavunikulam, and Rajangane, lift-irrigation is being practised. Here, it is concentrated on furrow-irrigated chillies and onions. As the irrigable area is located a t a higher elevation than the waterway, the water is lifted up by diesel pumps and made to flow under gravity.

4.4 CLASSIFICATION OF IRRIGATION WORKS

Irrigation works in Sri Lanka are classified from an engineering perspective into three main groups (Ponrajah,l982), namely, Village, Medium and Major irrigation works.

Village Works are those which serve a command area less then 80 ha (or 200 acres). Traditionally, under a Village Work, deliveries of water are made from a supply canal to a block of several holdings and to individual holdings. A Village Work also has the function of providing drainage facilities, mitigation of' floods and control of erosion through trapping silt in the reservoirs, The chains of tanks, which are constituted by Village Works, now referred to as 'cascades' have attracted attentioninrecent years (MaddumaBandara, 1985, Sakthivadivel et al. 1996)

Medium works are those schemes which assure irrigation waters or provide flood mitigation to an area of over 80 ha (200 acres) but less then 600 ha (or 1500 acres). New farms under a medium reservoir are supplied with water from a network of canals on an individual basis. The existing lands that are incorporated under a medium reservoir may follow the traditional pattern of irrigation as in village works or be converted to the pattern of irrigation as for new lands.

PfUZTIIA AtANCHANAY/UCE & C.M. IlIAI)I)UAIA BNVL)fLI<A

Major works are those which assure irrigatiofi waters 01% provide flood mitigation measures to an area above 600 ha. The pattern of irrigating farms of' new and existing lands under a major reservoir would be the same as for a medium reservoir.

This categorization holds good for anicut schemes as well. However, in recent times, exceptionally large projects such as Gal Oya, Walawe and Mahnweli have been classified as special projects. In addition, a number of lift-il-rigatio~~ projects form another category.

Agro-wells are a category of lift irrigation which had been confi~led nlainly to the north until recent years (Madduma Bandara, 1979). At present, t11e1.c is an attempt to introduce agro-wells in other areas of the dry zone too with foreign funding and expertise. The environmental effects of agro-wells such as tube- wells which mostly provide domestic needs are still not adequately understood and have become a subject of debate in recent years.

4.5 EFFICIENCY OF WATER USE IN IRRIGATION

Efficient water use or water management can be described as the application of irrigation methods, including timing, form layout, design of' system with the objective ofmakingthe best use of available water for agricult~~ral production. Water Management involves institutional mechanisms, flu,n~c~. participation, and agronomic considerations.

From the above statement it is clear that mere provision of an irrigation system and distributing water to the field is insufficient. The relationship between water supply, distribution systems, methods of irrigation and periods of irrigation, climatic conditions, soil properties and the kind of crop cultivated, cultural practices and other social factors must be understood and integrated fbr proper management. Agricultural inputs such as fe

r

tilizer, disease and pest control measures and improved seeds must be delivered at optil~~urn level. Farmer participation and adherence to cultivation schedules is vital in cf'ficicnt water management.

Efficient water management also depends upon the knowledge of water requirements of the particular crop grown in order to obtain the maximum yields without any adverse effects on soil properties or on the crop itself. I t includes the amount of water required to allow for evaporation, transpiration and metabolism of the plant (all these factors combined are commonly refcrred to as "consumptive use"), losses during conveyance and application of water, and the water needed for special operations such as land preparation. The water

a Lon wrrtcl. requirement for plant growth includes effective rainfall and irrig t '

WATER RESOURCES OF SRI WVKA 75

needs. The consumptive use of water can be determined by experimental methods, and the only variable factor in consumptive use is the evaporation, which depends on climatic conditions. Excessive irrigation is as bad as insuffi- cient application of water to the crop.

The irrigation water requirement could be minimized by reducing the conveyance losses in the field, and by crop diversification and cultiv t ' on practices. The following are some of the constraints to efficient water use:

(i) (ii) (ii) (iv) (v)

excessive as well as inadequate irrigation water, loss of water through conveyance and seepage, cultivation of heavy duty and long-term varieties, non-adoption of cropping patterns according to soil types, deterioration of physical properties of soil by keeping the soil continuously wet, cropping without using adequate organic manures, institutional inefficiencies, and lack of farmer cooperation, particularly in adherence to other cultivation programmes.

The cultivators often tend to over-use water in flood irrigation, due to continuous flow ofwater andbadly constructed levees and paddy plots (liy addas), These not only result in wastage of water, but also in poor yields due to water- logged conditions and development of salinity. The physical condition ofthe soil is also affected. The flooding of paddy fields is also supposed to help in weed control and aeration of the paddy plant by continuous replacement of standing water. However it is seen that even with flood irrigation most of the fields are heavily infested with weeds. It is questionable whether the use of preujous irrigation water for this purpose is justifiable when manual weeding is morc efficient. Better aeration can also be achieved by intermittent irrigation .

Regarding conveyance and seepage losses, it is only possible to reduce losses by proper irrigation management. Canal lining would help the rotational issues, in that water could be conveyed to fields quicker than by unlined canals. However, the cost of lining canals is quite heavy.

Farmers often tend to go for heavy duty and long-term varieties of rice. They also tend to ignore the existing soil type, and do not exercise care in adopting the appropriate cropping patterns. Farmers may have their own reasons fbr such practices, but adjustnlent of cropping patterns according to the available soil textures and using short-term varieties of paddy could increase water-use efficiency significantly.

76 PUZTHA M A h W H A N A Y M & C.M. M A D D U M A UU4Nl1ABi\

Keeping the soil continuously wet throughout the year can causc deterioration of the physical properties ofthe soil, and large quailtitics oforganic manure have then to be used in order to regain lost fertility. Generally, when t l ~ c physical condition of the soil deteriorates, its water bearing capacity would decrease, resulting in the excessive use of water. Therefore, when intensive cultivation practices are adopted throughout the year, organic manure has to be used liberally.

4.6 PROBLEMS ASSOCIATED WITH IRRIGATED AGRICULTURE

A few decades ago, crops were cultivated only once 8 year. Insects, pests and other disease-causing organisms could not reach harmful levels as food materials to support them were not available throughout the year. When farmers took up double cropping, when increased amounts of irrigation watcr became available in most parts of the country, the situation changed. Food material was available for insect pests and other organisms to survive for longer periods of time. Furthermore, the varieties of paddy that were cultivated were not resistant to most pests and diseases. This led to a considerable increase in the pest population.

Because the chemical fertilizers were more efficient than organic ma- nure, farmers were encouraged to use them. Thus large amounts of artificial fertilizers were applied to the soil. While this accelerated the growth 01' crop plants it resulted also in an increase in the growth of weeds and a multiplication of pest and disease-causing o

r

ganisms.

Agricultural activities generally pollute rivers and waterways. Soil erosion leads to sedimentation. The waters that become polluted by crop fertilizers such as nitrates tend to enter the water bodies, thus increasing the nitrate concentration. I t has been found that the concentration of nitrates has risen to very high levels in the Jaffna Peninsula. A high level of'nitratcs in water is found to cause a condition called "methaemoglobinaemiu" or blue baby syndrome amongst those who use such contaminated waters.

Somc ofthe available estimates indicate that as much as 60%. oof'the total water used inirrigationis lost due to evapo-transpiration, thereby increasing the salt concentration in the return flows off the irrigation area. If return flows are re-used many times high levels of salinity may result. Therefore, it is necessry to monitor and measure changes in water quality.

Several suggestions have been made to overcome these problems. The rates of nitrogen and other fertilizer use should be adjusted to meet crop needs more precisel y, especially on slopinglands in high-rainfall areas. Fertilizers li kc

WATER RESOURCES OF SRI M K A 77

the ammonium salts that are adsorbed by soils would be more suitable. Also, the use of pesticides should be minimized as far as possible., Soil conservation measures, should be used to reduce soil erosion and water runoff from cultivated lands.

4.7 CROP WATER REQUIREMENTS

Water is supplied to crops to meet the evapo-transpiration demand. This is the total water lost through transpiration via the stomata of leaves and evaporation from adjacent soil surface. Transpiration is primarily affected by climatic factors, among which solar radiation is the most important. I t has also been realized that actual transpiration rate is affected not only by the type of crop, but to a considerable extent by extent of the canopy. Regarding type, it is known that for C, crops water-use efficiency ranges from 300-800 while for C, plants the range is 150-300. I t has also been realized that the soil moisture status does influence the transpiration rates, and that ifthe soil is dry, the water cannot be transported into the leaves in sufficient quantities to meet the transpiration requirements. At this stage the stomata close and photosynthesis and transpi- ration of plants are reduced. Thus, when plants are not supplied with sufficient moisture, the growth of the crops as well as the yields is adversely affected.

For efficient water management, the evapo-transpiration needs of crops will have to be determined. In this connection, different empirical methods, such as the modified Penman and the Blaney Criddle, are being used. The evapo- transpiration or the consumptive use of water by a crop is the depth of' water consumed by evaporation and transpiration during crop growth, including the water consumed by accompanying weed growth. Once the consumptive use of' the crop is known, water use over large acreages can be calculated.

Some of the factors that affect the evapo-transpiration are:

rate of evaporation, mean monthly temperature, growing season of crop and cropping pattern, monthly precipitation in the area, irrigation depth or the depth of water applied for irrigation, wind velocity in the locality, soil and topography, irrigation practices and methods of irrigation, and sunshine hours.

78 PALZTHA MANCHANAYAKE 6r C.M. MADDUMA BANDARA

In order to estimate the evapo-transpiration of diff'ercnt crops, soil scientists have defined a 'Reference Crop', which is short grass. Tlw cvapct- transpiration of other crops is obtained by multiplying the values of' the "Referencc Crop" by a Crop Factor. The evapo-transpiration of t hc "Rcfei.cncc Crop" (ETO), computed for different regions is given in Table 4.1 (Dimantha and de Alwis, 1985). The growth of the crop to maturity is usually considcrcd to bc in four stages, namely, the initial stage, development stage, middle-stage and the late stage. The evapo-transpiration of the crop differs according to growth stage and a crop factor is assigned for each stage of growth. These crop factors are specific for each crop and for each growth stage in which they are considered. Table 4.2 gives the growth stages, their durations and the crop factors for a number of crops that are grown in Sri Lanka. Thus for a selected crop, thc crop- water requirements are calculated by multiplying the evapo-transpiration of the* "Reference Crop" (ETO) by the respective crop factors.

The cropping pattern usually indicates the sequence in which the crops are to be grown during the year. I t is prepared on the basis of thc suitability oL' crops that could be grown on different classes of soil that are present in an irrigable area. In preparing the cropping patterns, consideration would be given generally to such factors as crop preferences in the project area, the sufficiency offood crops to meet the demand and the financial returns that could be expected from cultivation. The croppirlg calendar shows the commeiicement and corn ple- tion times for the growing of crops according to an adopted cropping pattern. 'Yhc cropping calendar is generally prepared on the basis of the climatic collditions of the project area and the proposed cultural practices,

TABLE 4.1: Estimates of Reference Crop Evapo-transpiration for various Regions of Sri Lanka ? 2 Reglon Station Method of Reference Crop Evapo-transpiration (mmiclay) 23

Computation 2 U

Jan. Feb. Mar. Apr. May June July Aug. Sep. Oct. Nov. Dec. s 8

1. Dry Zone Low- Country RBE Anuradhapura P 4.0 5.0 6.0 6.0 6.0 6.5 6.5 6.5 6.5 5.0 4.0 4.0 $ 2. Dl-y Zone Low- Country RYL Kankesanturai P

8 5.5 6.0 6.5 7.0 7.0 7.0 6.5 6.5 6.5 5.0 4.5 4.5 cr,

3. Dry Zone Low-Country NCB Batticaloa P 5 4.5 5.5 6.0 6.0 .6.5 6.5 6.5 6.5 6.5 5.5 4.5 4.0 t,

4a. Wet Zone Low-Country RYP Colombo P 5.0 5.5 6.0 5.5 4.5 4.5 4.5 5.0 4.5 4.5 4.0 4.5 % P

& 4b. Wet Zone Mid-Country RYP Peradeniya 5.0 5.5 5.5 5.0 5.5 4.0 4.5 5.0 4.0 4.5 4.0 4.0

4c. Wet Zone Up- Country RYP l'alawakelle P 3.0 3.5 3.5 3.5 3.5 3.5 3.0 3.5 3.5 3.0 3.0 3.0

4d. Wet Zone Up-country RYP Nuwara Eliya P 3.0 4.0 4.0 3.5 3.0 3.0 2.5 3.0 3.0 3.0 3.0 3.0

5a. Intern~ediate Zone Low-Country RBE Ratalagoda P 4.5 5.0 5.5 5.5 5.5 5.0 5.0 5.5 3.0 3.0 3.0 3.0

5b. Intermediate Zone Mid-Country RBE Badulla P 3.5 3.5 3.5 4.5 4.5 5.5 5.5 5.5 3.5 3.0 3.0 3.0

5c. Intermediate Zone Up-country RYP Diyatalawa P 3.5 4.0 4.5 3.5 4.5 5.0 5.5 5.5 5.0 4.0 3.0 3.0

RBE = Reddish Brown Earth; RYE'= Red Yellow Podzolic;

Attvis 11 985) P = Modified Penman Method;

RYL = Red Y ~ l l o \ ~ Latosol; NCB = Non Calcic Brown

S o ~ ~ r c e : Dinzcln tha & de

80 PALZTHA MANCHANAYAKE & C.M. MADDUMA BAND&

TABLE 4.2: Crop Coefficients for Crops at different stages of Growth

Initial Stage Development Stage Mid Stage Late Stage

Period Mean Period Mean Period Mean Perlod Mean Crop (days) crop (days) crop (days) crop (days) ctsop

coefficient coefficient coefficient coclliclent

Brinjal (I40 days) 30 0.5 45 0.75 40 1.0 25 0.85 Chillies (180 days) 30 0.65 30 0.85 90 1.0 30 0.90 Chillies (150 clays) 25 0.65 25 0.85 75 1.0 25 0.90 Cotton (180 days) 30 0.5 50 0.8 55 1.15 45 0.65 Cowpea (90 days) 15 0.7 25 0.9 35 1.10 15 I .OO Green Gram (75 days) 15 0.5 20 0.8 25 1.05 15 0.70 Groundnut (110 days) 20 0.65 30 0.8 40 1.0 20 0.80 Maize (110 days) 20 0.5 30 0.8 40 1.10 20 0.56 Onion (95 days) 20 0.6 45 0.75 20 0,95 10 0.85 Lowland Paddy (135 days) 30 1.0 40 1.15 30 1.20 25 0.90 Lowland Paddy (105 days) 20 1.0 30 1.15 30 1.20 25 0.90 Upland Paddy (135 days) 30 0.90 40 1.0 45 1.05 20 0.90 Upland Paddy (105 days) 20 0.90 30 1.0 30 1.05 25 0 90 Pasture Pineapple NA 0.5 NA 0.5 NA 0.5 N A 0.5 Potatoes (105 days) 25 0.5 30 0 ,8 30 1.1 20 0.7 Pulses (90 Days) 15 0.5 25 0.8 35 1.05 15 0.5 Sorghum (100 days) 20 0.4 30 0.75 30 1.05 20 0.5 Soya bean

(105 days) 15 0.65 20 0.85 50 1.05 20 0.75

Sugar Cane

(390 days) 30 0.6 45 0.95 285 1.15 :1 0 0.65

Tobacco NA 0.4 N A 0.8 NA 1.2 25 0.85

Tomatoes

(135 days) 30 0.5 40 0.8 40 1.0 25 0.6

Source: Dimantha & de Alwis (1985)

WATER RESOURCES OF SRI LANKA

4.8 HYDROPOWER

I t has been reported that the first public supply of electricity in this country was inaugurated in Colombo in the year 1895 by Messrs Bousteds of UK-a private firm. In 1927, the Government a t the time purchased an electricity system from the private enterprise that operated the system, and formed the Department of Government Electrical Undertakings (DGEU). In 1950, the first hydro-project, namely the Laxapana Power Scheme, Stage I, was completed, and had become operational. I t consisted of a concrete iravity dam a t Norton, 35 m high and 105 m long. I t has a 2560 m long and 2.7 m diameter tunnel carrying the water to the power house a t Old Laxapana. Stage 2A of this scheme was started in 1954 and completed in 1958. I t consisted of a dam across the Kehelgamu Oya about 8 km upstream of the Norton Dam at Castlereigh, which is about 46 m high and about 143 m long. It has a storage capacity of 54 millionm3, whereas the Norton Pondhad only 0.88 millionm3 storage. Castlereigh Reservoir regulates the Kehelgamu Oya flows and augments the Norton Pond.

The Wimalasurendra Power Station was constructed as Stage 2B ofthe Scheme, and it is situated on the right bank ofthe Kehelgamu Oya just upstream of Norton Pond. The work on this stage of development was started in 1961 and completedin 1965. It consisted ofthe construction of a horse-shoe shaped tunnel of 3.66 m diameter and about 6100 m long from the Castlereigh Reservoi

r

.

The work on the Maskeli Oya Project, Stage I, commenced in 1966, and was completed and brought into operation in 1969. The main features of the project were the construction of the Moussakelle Dam and Reservoir across Maskeli Oya, the Polpitiya Dam, the Polpitiya Power conduit and the Polpitiya Power plant. Moussakelle dam is a concrete dam rising to a height of 35 m and with a length of 188 m, and has a storage capacity of 109 millionm:' of water. The Polpitiya Diversion Dam is located on the Maskeli Oya just down-strcam of' Laxapana power plant. This dam, which forms the Laxapana Pond, collects the flows of the Laxapana power plant and that of Maskeli Oya, to cater to the Polpitiya power tunnel. I t also does a short-period flow regulatioil by its limited pondage. It is a concrete gravity dam about 30 m in height and 130 m in length. The Polpitiya power conduit is about 4.7 m in size and is about 7750 m in length. The Polpitiya power plant has an installed capacity of 75 MW with two 37.5 MW, Francis Turbines.

TheMaskeliyaproject, Stage 2, was in connection with the New Laxapana power plant, which has an installed capacity of 100 MW with a rated head of578 m. This was commissionedin 1974. The Canyon Project Stage 1 and 2 has a total installed capacity of 60 MW, with a rated head of 204 m. The Canyoll Project was commissioned in 1982183. Thus, the hydropower potential in thc

82 PALITHA MANCHANAYAKE & C.M. MADDUMA BANDABA

Kelani river basin up to the confluence of the Kehelgamu Oya and Maskeli Oya streams has been completely exploited with the completion of the Canyon Project.

Under the first stage of the Mahaweli development project, the Polgolla Barrage was constructed for the diversion of water from the main Mahaweli Ganga to the Amban Ganga, through a 38 MW power station at Ukuwela which was commissioned in 1976. Here the water is diverted through a 8 km long tunnel constructed from Polgolla to Ukuwela. The next stage was the construc- tion of the Bowatenna reservoir of 33 million m3 of active capacity. It has two tunnels, one for irrigation releases catering to the three tanks, Dambulu Oya, Kandalama Wewa and the Huruluwewa, and has a maximum discharge capac- ity of 28.3 cumecs. The other, which is known as the power tunnel, takes water to the Bowatenna power station which has an installed capacity of 40 MW. This was commissioned in 1981. Further development came under the "Accelerated Mahaweli Development Programme", where three major power stations, namely Kotmale, Victoria and Randenigala were constructed. The Kotmalc power plant has an installed capacity of 134 MW, Victoria has 210 MW and Randcnigaia 122 MW. The power generation in Victoria commenced in November 1984. and Kotmale and Randenigala comrncnced in May 1985 and September. 1986, respectively.

4.9 PRESENT POWER FACILITIES AND POTENTIAL HYDROPOWER RE- SOURCES

Sri Lanka a t present has a total installed capacity of 1441 MW, with the completion of the Rantembe and Samanalawewa power projects. The Rantcnlbc project has an installed capacity of 49 MW and Samanalawewa has 240 MW.

Table 4.3 gives a list of the power generation projects as a t present, and the likely projects that are to come up in the near hture.

WATER RESOURCES OF SRZ LANK4 83

TABLE 4.3: Power Generation Projects in Sri Lanka

Name of Project Type Installed Capacity

(MW)

1. Old Laxapana 2. Inginiyagala 3. Udawnlawe 4. Wimalasurendra (Norton Bridge 5. PoIpitiya (Maskeliya Oya Stage 1) 6. New Laxapana (Maskeliya Oya Stage 11) 7. Ulruwela (Polgolla) 8. Bowatenne 9. Kelanitissa (Grandpass) 10. Kelanitissa 11. E'ettah 12. Chunnalram 13. Canyon 14. Victoria 15. Kotmale 16. Randenigala 17. Ranlambe 18. Samanalawewa

Future Projects Possihle

1. Broadlands 2. Caledonia/Talawalrellc 3. Kulrule 4. Ratnapura 5. Uma Oya 6. Jasmin

Hydro Hydro Hydro Hydro Hydro Hydro Hydro Hydro Steam

Gas Turbines Diesel Diesel Hydro Hydro Hydro Hydro Hydro Hydro

Hydro 30 Hydro 230 Hydro 180 Hydro 40 Hydro 130 Hydro 90

Table 4.4 gives a list of salient features of the existing and future hydroelectric development projects. Underthe new projects, the Samanalawewa project in the Upper Walawe basin seemed very promising, with an installed capacity of 240 MW. However, the technical feasibility of this project, particu- larly its dam foundation where serious problems ofwater leakage have deve-loped has drawn much public comment and criticism. The other proposed projects are Caledonia, Talawakelle, Upper Uma Oya, Lower Uma Oya in the Mahaweli Basin; Kukule and Ratnapura Reservoirs in the Kalu Ganga basin; the Broadlands Reservoir i n the Kelani basin; and the Jasmin Reservoir in the Gin Ganga basin.

84 PALITHA MANCHANAYAILE & C.M. MADDUMA BANDARA

However, the environmental impacts of these projects must be carefully as- sessed, before launching them.

TABLE 4.4: Salient Features of the Existing and Future Hydro Electric Devel- opment Projects

Name of Project River Installed Average Full Load Gross Nett Head L)am Reservo~v Basin Power Energy Flow Head (rn) Height Ciipacity

(MW) (GWH) (Cumecs) (m) (m) (Active)

(MCM)

1. Old Laxapana Kelani 2x125

2. Norton Kelani 2x25

3. Canyon Kelani 2x30

4. New Laxapana Kelani 2x50

6 Polpitiya Kelani 2x37.5

6. Ukuwela Mahaweli 2x20

7. Bowatenne Mahaweli 1x40

8. Victoria Mahaweli 3x70

9. Kotmale Mahaweli 2x67

10.Randenigala Mahaweli 2x61

.ll.Samanalawewa Walawe 3x80

12.Caledonia Mahaweli 2x25

13.'I'alawakelle Mahaweli 3x60

I4.Uppef U m n

Oya' Mahaweli 2x40

15.Lower Uma

Oya" Mahaweli 2x25

16.Kukule" Kalu 3x60

17. Jasmin' Gin 2x45 268 226.37 52 49 59 986.44

18.Rantambe Mahaweli 2x243 279 179.68 35 34 44 16 95

19.Broadlands' Kelani 2x10 105 56.59 47 47 44 4 3%

20 Heloluwa" Mahnweli 2x15 118 70.74 20 19 21)

2l.Ratnapura' Kalu 2x20 128 9.55 58 67 78 240 44

Note : 'Proposed hydroprojects.

WATER RESOURCES OF SRI LANK4

4.10 USE OF WIND ENERGY FOR LIFTING WATER

The use of wind energy in harnessing the water resources has received considerable attention in the recent past. The wind, which is a natural source of energy, is available in plenty in Sri Lanka. Being an island in the Indian Ocean and by virtue of its geographical location, Sri Lanka experiences strong south- west winds during the period from May to September, and nortl-r-east winds during the period from October to March. The average speeds of' these winds have been found to vary from 3 mls in the eastern coast to about 6.5 m/s in the southern coast. Thus, the prevalence of such strong winds in the dry zone during the drought period, could be made use of in lifting water off a well, stream or canal. This technology ofusing windmill pumps is a promising alternative to the conventional engine-driven pumps.

In 1978, a project for harnessing wind energy for lifting water was

undertaken by the Water Resources Board, with the assistance of the Govcra- ment ofthe Netherlands. I t was basically to study the feasibility aspects and to develop the appropriate technology.

The project proved fairly successful and the Water Resources Board has been implementing a n extension programme for promotion of windmill pumps in Sri Lanka. A reliable and cost-effective windmill pump which could be produced locally and used for small-scale lift irrigation purposes has been introduced by them, and it has been fairly popular. I t is estimated that there are over one hundred windmill pumps installed in different parts of' the counti-y which provide water for irrigation and domestic purposes in areas of water shortage. This has been particularly so in Hambantota, Vavuniya, Kataragama and Wellawaya areas.

4.11 SEWAGE AND WASTE DISPOSAL

The National Water Supply & Drainage Board is involved in improving the sanitary situation in urban areas. The policy, in general, is to use low-cost sanitation methods such as improved soakage pit systems and septic tanks in place of pit latrines. However, in very heavily populated areas, a sewer system of the low-cost sanitation method cannot be applied. The provision of sewer systems is fairly costly and the operation is also complicated. The city of Colon1 bo has been having a piped sewer system since the 1890s, and it is now being expanded to cover the Greater Colombo area. More cities, such as Kandy, Galle and Negombo, are likely to be provided with this facility in the future.

Generally, the sewage of Colombo and many other major cities is disposed in the sea, and i t is one of the largest sources of pollution to the coastal waters. The Wellawatte Canal, which takes most ofthe city effluents of Colombo,

86 PALITHA MANCHANAYAKE & C.M. MADDUMA BANDARA

is another source of pollution. Furthermore, a number of outlets carrying untr'eated sewage which is dumped into coastal waters are still found along the beaches of Colombo. In most coastal towns, and even fi-om large hotel complexcs, it is not uncommon to direct the untreated sewage and waste water into the sea. In general, pollution of urban waterways is one ofthe most serious environmen- tal problems in the country today.

Storm water disposal had become a serious problem in the Colombo city in recent years experiencing what has been termed as 'urban floods'. This is a result of urban expansion creating more impermeable surfaces particularly on reclaimed low lands. The original storm water disposal drains cannot cope with increasing s~irface water flows.

4.12 WATER USE FOR OTHER PURPOSES

Inland fishing in irrigation and hydropower reservoirs lias come into prominence in recent times. The Fisheries Ministry has taken up projects to introduce new varieties of freshwater fish to most of the irrigation reservoirs, including the Mahaweli reservoirs, in order to supplement the income of settlers by fishing. As the cultural aspect of the promotion of inland fisheries also deserves serious consideration, the Government had withdrawn State involve- ment i n such projects a t one stage. The promotion of aquaculture has several hydrological impacts leading to floods and deterioration of water quality.

Another useful purpose of large water bodies would be the recreational aspect for the tourist industry. Recreations such as boating, swimming and surfing in large reservoirs, and their tourist attractions could be referred to as secondary and intangible benefits, in addition to the primary benefits from irrigation and hydro-power generation. However, the concern for environmental aspects has brought reservoir-based hotel projects to public scrutiny in recent years. The Kandalama and Rajawella Hotel projects thus generated much debate and public concern.

The water-based industries that could be started near these large water bodies form another potential use of water resources. Usage ofinland canals for navigation is another use which was important historically, as exemplified by the Hamilton Canal which connected Colombo with northern coastal cities. As an Island Sri Lanka has not utilized the potential for water-based tl.anspol-ta- tion. If this could be improved much of the congestion an highways particula~.ly caused by heavy vehicles can be reduced significantly.

The production of drinking water in bottled form is the most recent development in the water industry. Sri Lanka with so many springs has a great potential for this industry.

CHAPTER FIVE

Water Laws and State Policy

5.1 STATE POLICIES

As water is a limitednatural resource which is essential for the existencc ofhuman and animal populations and plants, the State exercises full control over the determination of priorities of its use. The various development programmes dealing with water, such as the Mahaweli project, are dra~vnup by the individual Government Departments, Corporations or Authorities, and are submitted through their Ministries to the Ministry of Finance and Planning. These programmes are subsequently presented to the Cabinet of Ministers and Parliament for final approval.

The determination of priorities is undertaken by the Government, both on a project-wise and area-wise basis. However, there is no regulation or law governing the priorities of supplies of water to different areas in Sri Lanka. Selection of priorities for implementation and the sequence of developmcnt arc based on the evaluation of the projects in terms of the returns that accrue to the particular areas taking due cognizance of the need to develop certain totally neglected and underdeveloped areas.

5.2 WATERLAWS

Riparian and Appropriative Rights

Basically, there are two doctrines in stream-water rights that are being adopted in different parts of the world, namely, 'Riparian Rights' and ' Appropriative Rights'. The doctrine of riparian rights was derived from French civil law, in the early nineteenth century. Subsequently, it was adopted by the English courts, incorporating it into the English common law. Under the concept of riparian rights, the owner of a land adjacent to a stream is entitled to receive the full natural flow of the stream without any change in quality or quantity. The riparian owner is protected against the diversion of waters upstream of his property, or from the diversion of excess flood waters towards his property. In other words, a n upstream owner may materially lessen or increase the natural flow of a stream to the disadvantage of a downstream owner.

The riparian doctrine has serious deficiencies in its application to modern society. I t does not provide for actual use of water by the riparian owners for irrigation or other purposes. Consequently, the riparian concept has been

88 PALITHA MANCHANAYAKE & C.M. MADDUMA BANDARA

modified to permit a 'reasonable use' of water. 'Reasonable use' allows riparian owners to divert and use stream water in reasonable amounts for beneficial purposes. In regions of ample flows, this permits riparian owners to use all the water they need, but if the flow is inadequate for all owners, the available water must be divided on some equitable basis. However, an upstream owner may always use as much water as he needs for domestic use and for watering domestic stock. Such use is considered as 'ordinary or natural use'. Irrigation or provision of water for commercial herds of stock is not considered a 'natural use' and therefore not entitled for preference. The reasonableness of use of water is usually being determined by factors such as the area, character of the land, importance of the use and the possibleinjury or damage to other riparianowners. No priority or right could exist between the riparian owners. In other words, all riparian owners have equal rights to a reasonable share of water, and no owner can exercise his rights to the detriment of others. When riparian rights are transferred, the new owner must adhere to the conditions that governed the original owner.

A riparian right exists in the land and is not affected by the use o r lack ofuse. The riparian rights can be lost by upstream adverse use wliich ripens illto a prescriptive right at the end of the period specified under the statute of limitations. If riparian property is sold, the right is automatically transferred to the new owner. If a parcel ofriparian land is divided, any section not adjacent to the stream loses its riparian status unless the right is specifically preserved in the conveyance. The riparian rights do not exist in artificial challl~els and drainage ditches unless by long existence they develop characteristics of'nat~ual water courses.

The concept of'appropriative rights' came from the Roman civil law and it has been used in the United States, especially in states such as Colorado, Ncw Mexico and Arizona. The main feature of the doctrine of appropriation is the concept of 'first in time, first in right'. The right of the earliest appropriator is superior to any other claim, and further appropriation is possible only if water in excess of earlier claims is available. During water shortages, the available supply is not apportioned among all users. Instead, those claimants with the earliest priority are entitled to their full share, and those with later priorities may have to do without.

Under an exclusive system of appropriative rights, all water in natural water courses is subject to appropriation. An appropriator may store watcr in reservoirs for use during periods of shortage, but the amount stored is limited by the terms of the storage appropriation. The reservoir releases intended for downstream use belong to the person storing the water or those to whom it is consigned and may not be appropriated. The appropriated water may be used

WATER RESOURCES OF SRZ LANKA 80

on lands away from the stream as well a s on lands adjoining the stream. The earliest appropriator in point of time has thc exclusive right to thc! use of his appropriation without diminution of quantity or deterioration of' q ual i ty when- ever the water is naturally available.

5.3 LEGISLATlON IN SRI LANKA

In Sri Lanka, several laws have been enacted for the control and effective use of water. They have been amended from time to time to meet with situations caused by the institutional changes that are taking place in the country.

The major laws dealing with the utilization of water resources, either directly or indirectly, which are in force in Sri Lanka are given helow:

Legislation in Force (1993)

(a) Administered by Government Departments:

1. Irrigation Ordinance, No 32 of 1946, a s amended in 1968. 2. Paddy Lands Act No.1 of 1958, a s amended in 1958,1961 & 1964. 3. Agrarian Services Act of 1979, a s amended in 1990. 4. Crown Lands Ordinance No.8 of 1947, No.9 of 1947, Act No.13 of'1949, 1956

Revision, 5. Land Development Ordinance No. 19 of 1935, No. 3 of 1946, Act No. 49 ot'

1953 and Act No. 22 of' 1955,1956 Revision. 6. The Walawe Lands Act No. 11 of 1958 (Amending the Land Acquisition Act) 7. Land Acquisition Act No.9 of 1950. 8. Housing and Town Improvement Ordinance No. 19 of 1915 and subsequent

amendments, 1956 Revision. 9. Soil Conservation Act No. 25 of 1951 and 29 of 1953, 1956 Revision. 10. Fisheries Ordinance, No. 24 of 1940 and subsequent amendments (Chap.

21 1 of the Legislative Enactments of Ceylon), 1956 Revision. 11. Factories Ordinance No.45 ol'1924 and No. 22 of 1946 (1956 Revision), and

Factories (Amendment) Act No.54 of 1961. 12. Public Works Loan Ordinance No. 6 of 1909,6 of 1921,26 of 1929, 5 & 6 of

1937,52 of 1944 and Act No. 11 of 1949 with 1956 Revision. 13. Thoroughfares Ordinance, Chapter 193. of 1862,1956, Law no. 37 of 1973.

1981 of 1988. 14. Agricultural Productivity Law No. 2 of 1972. 15. Agricultural Insurance Law No.27 of 1973. 16. Agricultural Land Law No.42.of 1973. 17. Sale of State Lands (Special Provision Law) No.43 of 1973,

90 PALITHA MANCHANAYAKE & C.M. MADDIJMA BANDAI?A

(b) Administered by Public Corporations:

18. Gal Oya Development Board Act. 51 of 1949 and No. 40 of' 1952, Revised 1956, and amendments of 1961.

19. River Valleys Development Board (Amendment) Act No. 6 of 1956. 20. Water Resources Board Act No. 29 of 1964. 21. Development Finance Corporation of Ceylon Act No. 35 of 1935 and subse-

quent amendments. 22. Land Reform Law No. 1 of 1972. 23. Agricultural Corporation Act No. 11 of 1972. 24. Mahaweli Development Board Act No. 14 of 1970,3 of'1976, and 38 of'1983. 25. Mahaweli Authority Act No. 23 of 1979 and 59 of 1993. 26. Colombo District (Low Lying Areas) Reclamation and Developmel~t Boarcl

Act 1968, and Amendment Act No. 52 of 1982. 27. Ceylon Electricity Board Act of 1956 and 1969. 28. National Environmental Act of 1980 and its amendments.

(c ) Administered by Local Bodies

28. Urban Councils Ordinance No. 6 1 of 1939 and subsequent amendments. 29. Village Communities Ordinance (Chap.198) of 1924,1956, No. 35 of'1957,7

of 1959. 30. Town Council Ordinance No. 3 of 1946 and subsequent amcl.ndmcnts, 1956

Revision. 31. Municipal Councils Ordinalice No. 29 of 1947 and subsequent a~llendme~lts

of 1956, 1957 and 1958.

5.4 OWNERSHIP OF WATER

The ownership of water in Sri Lanka is generally governed by the customs of the people and the legal enactments of the country. However, the customs and the cultural practices that have stood long in the country play a more vital role than the mere enfbrcement of the laws.

The type of system that prevailed during the times of thc anciel~t Kings for the strict control of'operation and maintenance of irrigation pt.qjccts could be well illustrated by the fbllowing:

" ... that all holders of lands benefitted were bound to take an equal share in the repairs of the irrigation channel. Each proprietor was responsible for the proper repair of a certain portion of the clzannel, and sudden unforeseen accidents were repaired by the joint labour of ull, as was also the dam or in the case of a tank, the bund. No person was entitled to water if kc. neglected to contribi~te to the repu11-s of'tl~e

WATER RESOURCES OF SRZ LANKA

dam 01. chalznel, and no new land could be cultivated to the detrrrr~elzt of t l ~ e existing.fields. The fields at the end oftlze ckannel wereploi~glzed first, and the rest zrpwards i n regular order; and i f tlze lowest fielcls were not ploughed at the proper season they lost their right to priority of water. During tlze dry season the fields were irrigated by rotation, commencing with those at the commencement of the channel (or nearest to tlze bund, as the case may be). When the volume of any szrpplying stream was inszrfficient for tlze irrigation of all tlze lands dependent on it, they were divided into portions of szrclz extent as would permit each being properly irrigated, and these portions re- ceived the whole volzrme of the water dzrring szrcceeding seasons i n rotatiori. T l ~ e charznel was iwpected daily, and if any fields were foirrzd irrigated out of its proper rotation, the proprietor was held guilty of theft of water. Any violation ofthese regulations was pronzptly punished by the imposition ofa fine, and i f a royalprison was at hand, by imprisonment also". (Sr i Lanka Cozrntry Report for the UN Water Conference, 1977).

5.5 WATER RIGHTS

The Crown Lands Ordinance defines a public stream as ally river, stream or ela flowing into or from a natural channel, provided tha t the source and the entire coil rse of' such stream is not situated within a private land. The public ownership of water is not confined to rivers only, but the same principle applies in the case of stored water in lakes and reservoirs. Similarly, a private stream could be categorized as any stream where the source and the entire course are located within the private lands and thus become a matter of private right.

The right to use, manage and control water in any public lake or stream has been vested in the State under Section 72 of the Crown Lands Ordinance. The State could exercise this right, provided its actions do not contravene any already granted right or where otherwise allocated by law or vested with any person. Corporate body, Board, Corporation or Local authority, and do not become prejudicial to or a denial of the rights of the occupiers of' such lands on the banks of lakes or streams. It shall also not deny the use ofwater fbr domestic purposes and for use by domestic livestock.

In exercising the above right, permits may be issued for the use of water owned by the State. The Divisional Secretaries, who are the general administra- tors a t the district level, are delegated with the function of issuing such permits, which may also be for the diversion of any water from publiclake or public stream and construction of any work for such purpose. Those permits carry certain conditions which are obligations on the part of the permit holder. A prescribed

92 PALITHA MANCHANAYAKE & C.M. MALIDUMA BANIMl<A

fee is also levied for the issue of such permits. Non-compliance with thc conditions therein or it being found that the permit holder was abusing the= privileges granted by the permit, the permit may be cancelled and legal action taken where considered appropriate. When water rights are vested with local authorities like Municipal, Urban and Town Councils, and Pradeshiya Sabhas such bodies should have subsidiary legislation in the form of by-laws. The final authority for settling disputes arising out of these by-laws shall be the Minister of Local Government.

As per the Fisheries Ordinance, if one wants to use the public water fbr fishing as a commercial venture then he has to obtain the necessary permit from the agency to which the authority has been delegated.

The River Valleys Development Board (now liquidated) under the River Valleys Development Board Act of 1965, and the Mahaweli Authority of Sri Lanka under the Mahaweli Authority Act No 23 of 1979, have special provisions in the statute to exercise all authority over the rivers and the waters that are located in the areas vested in them. They are also empowered to regulate the use of water for irrigation, hydropower, industry, fishing, navigation, and for the imposition of water rates and prevention of pollution.

For private waters, which are defined as those bodies of'watcr that arc wholly located within the privately owned lands, no government authorizatio~l or permits are needed in using them.

5.6 SECTORAL LEGISLATION

The sectoral uses of water can be identified in the fields of agriculture and irrigation development, hydropower generation, industry, domestic usage and fishing. They are generally governed by different legal enactments which delegate the hnctions of control and administration of different waters to various government agencies that deal with them.

There are several legal enactments governing water use for agricultural and irrigation activities. Theuse of public water for such activities is fully under the control of the Government. Different Government and Corporate Agencies have been entrusted with the powers of enforcement of such enactments. A few important enactments are as follows:

(a) Irrigation Ordinance No. 32 of 1946 and its amendments, (b) Paddy Lands Act No. 1 of 1958, replaced by Law No. 42 of 1973,

No. 30 of 1958,61 of 1961, 11 of 1964,25 of 1966; Paddy Lands (Special Provisions) Act No. 2 of 1970.

WATER RESOURCES OF SRI LAN-

(c) Water Resources Board Act of 1964, (d) Mahaweli Development Board Act of 1970, (e) Agricultural Productivity Law of 1972, (f) Agricultural Development Authority Act of 1978, (g) Mahaweli Authority Act No. 23 of 1979, (h) Coast Conservation Act No. 57 of 1981 and 64 of 1988. (i) Agrarian Services Act No. 58 of 1979,9 of 1990,4 of 1991,40

and 41 (Special Provisions) of 1993 and its subseq~lent amend- ments.

The provision of irrigation facilities for agricultural purposes is mainly under the charge of the Irrigation Department and the Mahaweli Authority of Sri Lanka. They generally make decisions in dealing with the overall policy as defined in the respective enactments. In the early days, the management of water for irrigation a t the village level was entrusted to the Ye1 Vidane' or the 'Irrigation Headman' who was a respected village elder appointed by the Government Agent. This system had its own shortcomings, and the Paddy Lands Act of 1958 as amended in 1964, replaced this system of one mall conti*ol. I t provided for the setting up of Cultivation Committees consisting of' clectcd representatives amongst the cultivators of a village, and delegated the power to control water distribution for agricultural purposes to such committees. The Agricultural Productivity Law of 1972 further introduced a system ofAgric~11- turalProductivity Committees which have, among many other functions assig~lccl to them, the management and distribution of water a t farm level, The Agrarian Services Act attempted to redefine the authority of the irrigation headmen in its subsequent amendments. The experience of the latter system, though more democratic, proved to be far from satisfactory in the overall ~nanagement of irrigation (Gunaratne & Madduma Bandara, 1987).

The legal enactments dealing with hydropower are covered by the Electricity Act of 1950, its amendedversionin 1957, the CeylonElectricity Board Act of 1959 and Act 17 of 1969. The generation of hydropower, the full cont1.01 of production andits distribution through the national grid of Sri Larlka lie in thc hands of'the Government and is exercised through the Ceylon Electricity Board.

The legislation for the use of water for industries is given under the Factories Ordinance as amended in 1961, which provides the safety measures that are to be followed in the use of water for industrial purposes. The water, after being used for industrial purposes, has to be often diverted back to the river or waterway, and it should be well below toxic levels for the downstream water users. The National Environmental Act and its subsequent amendment have strict stipulations against water pollution.

94 PALJTHA MANCHANAYAKE & C.M. MADDUMA BANDARA

The major enactments pertaining to the domestic usage of water are as follows:

(a) Housing and Town Improvement Ordinance No. 19 of 1915 and its subsequent amendments,

(b) Village Communities Ordinance Chap. 198 of 1924,1956, No. 35 of' 1957 and 7 of 1959 and its subsequent amendments.

(c) Urban Council Ordinance No. 61 of 1939 and subsequent amend- ments,

(d) Town Council Ordinance No. 3 of 1946 and subsequent amend- ments,

(e) Municipal Council Ordinance No. 29 of 1947 and subsequcnt amendments,

f) National Water Supply and Drainage Board Law No. 2 of 1974, and 13 of 1992.

The utilization, management and distribution of water supplies fbr municipal, urban and domestic purposes are generally being administered under the above legal enactments, under which the Local Government Bodies are empowered to make their by-laws in respect of any waters that may be vested in them. Most schemes of water supply for domestic purposes are generally constructed and supervised by the National Water Supply and Drainage Board. In the areas defined and vested with the Mahaweli Authority of Sri Lanka, the right to control and regulate water lies with them.

The legal enactment regulating fishing in ail its aspects is the Fishcries Ordinance No. 24 of 1940 and its subsequent amendments. This enactment provides for the catching and protection of fish, regulation ofthe fishing ind ustry and other activities concerned with fishing in Sri Lankan waters. Thc Minister of Fisheries is generally responsible for the administration and enforcement of these laws and he is advised by the Fisheries Advisory Board. Fishing for profit in Sri Lankan waters, namely in her territorial waters and in all inland waters, including rivers, reservoirs and lakes, can be undertaken only on a fishing licence. The use ofwater for fishingpurposes in the authorized areasvested with the River Valleys Development Board and the Mahaweli Authority of Sri Lanlrtl is governed by the by-laws of these respective organizations. Thc Coast Conservation Department is vested with the same authority in managing coastal watcrs, coming within the coastal zone as defined by the Act.

The harmful effects of water can be identified as flooding, soil erosion, siltation, salinisation and water logging. The Soil Conservation Act No. 25 of' 1951 provides for measures to prevent and mitigate soil erosion and for the protection of lands against damage caused by floods and droughts. I t is the duty of the Director ofAgriculture to investigate the nature and possible extent of soil

WATER RESOURCES OF SRI LANK4 95

erosion and the damage of lands and to enforce soil conservation measures to prevent them. Regarding the control of floods, drainage and reclamation of marshy lands, improvement of drainage facilities on irrigable lands and salt water exclusion from cultivable areas, the responsibility lies with the Irrigation Department. Similar activities falling within the areas of the Mahaweli Authority come under the purview of that authority.

5.7 WATER WASTE, QUALITY AND POLLUTION CONTROL

The Irrigation Ordinance No. 32 of 1946 and Act No. 1 of' 1951 and their subsequent amendments deal with the legal provisions concerning the preven- tion of waste and misuse of water. This specifically prohibits any water from being allowed to run waste, and in instances where the person responsible for such waste cannot be identified, the proprietor ofthe lands which received such water and derived benefit, shall be liable to pay for such water as determined by the Divisional Secretary of the area.

The Water Resources Board Act of 1964 has empowered the Board to draft legislation for the prevention of pollution and to take adequate steps to enforce such laws. The Central Environmental Authority can exercise much power in preventing pollution under the provisions of the National Environmental Act. 97.

CHAPTER SIX

Water Resources Management Institutions

6.1 EVOLUTION OF WATElt-MANAGEMENT INSTITUTIONS

Historically, the water resources projects were handled by the then Public Works Department (PWD) until the year 1899. In 1900, having felt the importance of the place of agriculture in the development of this country, the Government established the Irrigation Department in order to expedite thc investigation, design and execution of irrigation works. In the same year, the Department was shifted from Trincomalee to Colombo. The severe floods of January 1924, due to the breaching of many village tanks caused serious embankment washaways on the Northern Railway. Two serious train accide~lls occurred due to floods, resulting in the death of a number of passe11ge1.s. This disaster led the Irrigation Department to evolve a more scientific policy for ilic restoration and management of village irrigation works. Since then, the Irnga- tion Department has been the sole Government agency responsible for the investigation, planning, design, construction and maintenance of all types of water resources projects. However, subsequent changes had necessarily to follow, due to various other governmental agencies being called upon to handle water resources projects.

The Irrigation Department was assigned full control over the operatio11 and maintenance of the irrigation systems by the Irrigation Ordinance No. 45 of' 1917, which was superseded by the Ordinance No. 32 of 1946. The Ordinance ot' 1946, amended in 1951 and again in 1968, prescribed the procedure for mainte- nance and operation ofirrigation schemes, for distributionof water and proccd~~l*cu for collection of water rates from the farmers. The administration of the Ordinance was through the Government Agents, who were the revenue officers responsible for district administration. (Most of these functions are now handled by District and Divisional Secretaries.) However, the revenue officers were advised by the Irrigation Department, which set out the procedures for the protection of irrigation works and for the conservation of water. The date of' commencement of cultivation operations and the extent of land to be takcn u p for cultivation during a particular cultivation season were to be decided bcf01.t~ hand, at a meeting ofthe cultivators (referred to as Kanna meeting), on the basis of the recommendations made and on limitations set by the representatives ol' the Irrigation Department.

98 PALITHA M A N C H A N A Y m & C.M. MADDUMA BANDAIZ.4

When the Paddy Lands Act was enacted in 1958, the Cultivation Committees were given wider powers to regulate all irrigated cultivation, enforce cultivation rules, stipulate maintenance responsibility and impose irrigation rates. In 1970, with the formation of the Territorial Civil Engineering Organization (TCEO), the operation and maintenance functions of the irrigation schemes came under its purview, and in 1978, when i t was abolished, those responsibilities reverted back to the Irrigation Department.

The autonomous boards such as the Gal Oya Development Board, which was established for the implementation ofthe Gal Oya scheme, the River Valleys Development Board for the Uda-Walawe Project, the Mahaweli Development Board and the more recent Mahaweli Authority of Sri Lanka for the implcmen- tation of the massive Mahaweli Project, were responsible for enforcing the provisions of the Irrigation Ordinance in the schemes under their charge. Under the Thirteenth Amendment to the Constitution, the central government is primarily responsible for the 'inter-provincial irrigation projects'.

In dealing with the public water supplies, the responsibilities were shared by the local authority and the Central Government. The authority for control, use and distribution of water, levying of water taxes and their collection were vested with the local bodies. The Department of Water Supply and Drainage which functioned up to 1975, was replaced by the National Water Supply and Drainage Board, which functions as the single authority responsible for domestic water supplies and their disposal after use. I t is responsible fbr all matters connected with the development, construction and use of water for domestic and industrial purposes.

The Department of Government Electrical Undertakings (DGEU), which was established in 1927, was responsible for the development of hydro-electric- ity. I t functioned till 1969, when it was absorbed into the newly formed Ceylon Electricity Board (CEB), which is responsible for the generation, transmission and distribution of electrical power in the country.

The Water Resources Board, which deals with the conservatioll and utilization of water resources of the country, a t present concentrates on the exploration and exploitation of groundwater resources of Sri Lanka.

The link between the landlord and the paddy farmer cultivating private lands under irrigation works was established in 1958 by the Paddy Lands Act. The purpose of this legislation, among other things, was to provide security of tenure of tenant cultivators and to specify the rent payable by such tenants. I t provides the tenants with security of tenure which may be handed down to relatives or appointed successors. It empowered the Commissioner of the

WATER RESOURCES OF SRI LANK4 99

Agrarian Services Department to review cases of ejectment of tenant cultivators and to safeguard the lawful interests of the peasant cultivator. The Commissioner ofAgrarian Services was also empowered to eject either the tenant or landlord after due notice, if the land was not cultivated " i?~ accordance with tlzeprinciples ofgood paddy cultivation." He was empowered to determine the rent to be paid by the tenant cultivator on the paddy land. Though such rents could vary both between and within an administrative district, i t was limited to 15 bushels of paddy per acre, or one-fourth of the total yield, and was payable in cash or kind. The Paddy Lands Act was superseded by the Agrarian Services Act of 1979 and its subsequent amendments.

The land development works under the major irrigation and settlement schemes were the responsibility ofthe Land Commissioner's Department, which was required to administer and alienate Crown lands in such a manner that they would contribute to economic and social progress of the recipients. The regula- tion of tenure under the Land Development Ordinance (1935) and its amendments is also the responsibility of this Department. Most of these functions are now decentralized to Provincial administrations.

The clearing of land and the provision of infra-structural facilities necessary for settlement schemes, which were initially handled by the Irrigation Department, came under the responsibility of a separate Land Develqpment Department in 1947, which had been disbanded recently.

The agricultural development aspects of irrigation settlement schemes, including the extension and supporting services, are generally functions entrusted to the Department of Agriculture and Agrarian Services. Originally, the economic size of holdings of irrigated lands was considered to be 5 acres of paddy and 3 acres of highland, when the guidelines were established in this connection in 1930. Subsequently, in 1953, it was reduced to'3 acres of paddy and 2 acres of highland for the projects started thereafter. This was again reduced to 2 acres of paddy and 1 acre of highland in 1963. For the Mahaweli Project, it was decided as 1 ha (2.5 acres) allotments of irrigable area and 0.2 ha (0.5 acres) of highland, with adequate irrigation water for two crops per year. The gradual reduction in the unit size of irrigated allotments had significant implications for the management of water resources, as well as to the domestic economy of the settlers.

The Irrigation Department, which now comes under a separate Ministry, the Ministry of Irrigation, Fewer and Energy, is responsible for the following:

(1) Preparation of development plans for different river'basins for optimum utilization of land and water resources.

PALITHA MANCHANAYrUI% & C.M. MADDUMA WNVDAK.4

(2) Project formulation and preparation of detailed designs of rnajur irrigation, hydro-power, flood control and reelamation projects.

(3) Construction of majar irrigation projects, each ~f which cost over Rs,2.3 million for the conservation, diversion and distribution of water for the cultivation of irrigable lands under gravity irrigation.

4

(4) Construction of lift irrigation projects for the cultivation of subsidi- ary food crops under irrigation.

(5 ) Construction of flood protection, drainage and salt water exclusion projects, each of which cost over Rs. 2 3 million for the protection of cultivable lands and rendering them suitable f o ~ cultivation pur- poses.

(61 Providing consultancy services in the field of water resources deve- lopment to other government departments, corporations and other institutions.

(7) Carrying out applied research in the fields of Hydraulics, Hydrology, Engineering Geology, Soil Mechanics, Soil and Land Use and Agri- culture as relevant to water-resources development. The other important functions such as investigations, laboratory services aud land classification services are complementary to the main functions of the Department,

All preliminary and detailed survey work on these projects is done by the SurueyD@partmeat of the Government of Sri Lanka, and also by surveyors in the private sector authorized to undertake such works.

The DisErict Secretary of each District presides at regular meetings and has discussions with various officers of the district in planning a sucmssf~~l operation of the cultivation in each season. He takes into consideratiou tho cultivation practices of the locality and other aspects of cultivatiol~, a11d g 3 enel'- ally functions as a coordinator of' all government and other organizations of t l ~ c district. The Irrigation Ordinance provides for the constitution of a District Agricuttural Committee (D.A.C.) in each administrative district. This Commit- tee generally consists of district level heads of different agencies and departments which are directly or indirectly connected with water use and agriculture, and it advises the Divisional Secretary on matters related to irrigated agriculture. The Ordinance further includes provision for the convening of meetings of proprietors ofprivate lands and allottees ofsettlement schemes in order to decide on various issues that arise pertaining to the operation of irrigation schemes.

WATER RZSOURCES OF SRZ LANK4 101

The particular dates for the commencement of cultivation, ploughing, sowing, harvesting and the responsibility for maintenance of irrigation works are some of the issues that would be discussed. The distribution of water from major resewairs, anicut schemes, main and distributary canals would generally be done by the Irrigation Department, while the farmer organizations mobilize the cultivators for the work involved in distribution of water to the farms and i n maintaining the field canals leading up to the farm outlets. In recent times, farmers have been given increasing responsibilities in managing irrigation water.

The Land Detteloprnent Department was generally assigned the work related to the development of land and construction of buildings and roads in settlement schemes. The Department is now in the process of liquidation.

CHAPTER SEVEN

Towards a National Water Policy

Water as a vital natural resource has predominantly been under the control and care of the government. The government, continuing the colonial tradition discharged this responsibility primarily through legislation. Thus some of the existing water laws have stood the test of time and have helped the authorities concernedin the management ofthe key resouves ofland and water. In fact, thesc laws and regulations have been the mainstay of the provincial administration for a long time, and have been respected and accepted by t l ~ c public.

However, some amendments, both in order to close loop-holes whercver discovered and, more importantly, to meet the demands of a fast expanding economy were found to be necessary. With the rapid expansion of the need for water in the agricultural, hydropower and industrial sectors, competing de- mands for the allocation of water resources have increased among them. The existing institutional and legal provisions, which were formulated for different purposes in different economic environments in the past, have been found to be inadequate to cope with the present demands. As a result, conflicting and unhealthy situations in the allocation and use of the water resources have begun to thwart the development efforts and some of the major economic activities of the country. For this reason, the then ~ i n i s t r ~ of ~ a n d s and Land Developlncnt submitted proposals to enact a Water Resources Act, whose main features were:

(1) the setting up of a central body called the Water Resources Council to advise the Government on the establishment of a National Water Policy. This Council would formulate strategies for the efficient and effective allocation and development of the multi-purpose and inte- grated utilization of surface and groundwater resources in t l ~ c country;

(2) to mobilize and co-ordinate the efforts in all agencies connected with the allocation, management and development of water re- sources by enlisting the co-operation and assistance of thc Ministries concerned;

(3) to direct and undertake studies in matters related to the attainment of the principal objectives; and

(4) the setting up of Water Courts for the effective enforcement of thc legislative provisions by the implementing agencies.

104 PALITHA MANCHANAY- & C.M. MADDUMA BANDARA

The prerogative powers of the Government to allocate the water re- sources were to be exercised through this Water Resources Council, which was to be accountable to the Minister in charge of Water Resources Planniug, and through him to the Cabinet. The Secretaries of the line Ministries couoc~.~~i!d with water use were to be ex-officio members of the Water Resources C'ouncil. This Act was expected to enable the line Ministries to relate and reconcile tl lcir priorities with the overall objectives of the Government without leaving such matters to the initiative of the respective agency, in the manner they have hitherto functioned.

Subsequently, a more comprehensive Act covering related aspects of water use, soil conservation and land use was proposed. The Land Commission (1990) a t the same time recommended the establishment of a Watershed Management Authority.

With the commissioning of the largest multi-purpose vrater resources development project, namely the Mahaweli, the inter-regional and inter-district prio

r

ities in water allocation and utilization have assumed greater importance. These priorities will have to be matched with the national goals and objectives for the benefit of the greater interests of the community. Thus, a central allocating procedure would significantly enhance the quality of the decisions pertaining to such allocation and utilization of water resources. Any new legislation should not take away the powers vested in implementing agencies in matters concerning water resources development and utilization within their areas of authority.

After the completion of the Mahaweli Project, there will not be many attractive sites available for future development as major irrigation scllcmcs. Under the Mahaweli Development programme all major water resources projects, except Moragahakanda, have now been completed. With regard to other river basins, large projects are possible only in a few like the Kalu Ganga. In future, therefore there will hardly be any major water resources schemes for develop- ment, other than augmentation, rehabilitation and improvements to existing works.

In the major irrigation schemes, a significant potential for further development exists in increasing the efficiency ofwater management. Altllough this was not a serious major concernuntil the 1970s, much attention is being paid to this aspect through international organizations such as IIMI and national agencies such as the Irrigation Management Division of the Lands Ministry. There is also some NGO interest in this field. The improvement of' irrigation management should ultimately result in a significant reduction in the existing levels ofwater duty, which are certainly excessive. Current thinking is that this could be achieved only through a programme of dedicated farmer participation.

WATER RESOURCES OF SRI WVKA I05

Thus, there is a trend towards handing over many irrigation systems directly to farmer management.

In future much development potential in water resources will be fbund in the exploitation of groundwater resources and in the development of micro- catchments and mini-hydropower projects. For all such future developments, improved Watershed Management will become indispensable.

Some recommendations towards the development of' a National Water Policy are listed below.

(1) Formation of Farmer Organizations a t different levels for. manage- ment of the irrigation systems. Limited liability compar~ics of'li'arlnc~. Organizatiom or Societies have met with some degree of' success in the P

hi

lippines. The necessary legislative provisions are now available in Sri Lanka to set up farmer organizations under the Agrarian Services Act.

(2) Strict enforcement of laws to control the unauthorized tapping of' water from irrigation canals. Unauthorized tapping of water, leads to considerable waste and this seriously interferes with good water management.

(3) Strict enforcement oflaws to prevent squatters or cultivation of calla1 or stream reservations. This aspect has beenneglected in the past, and it has created problems in water management in the irrigation canal network.

(4) Watershed areas feeding the tanks and reservoirs should be strictly protected from squatters or inappropriate cultivation practices. Strin- gent laws should be enforcedin this connection and, wherever possible, these areas should be declared as forest reserves and re-afforestation programmes undertaken in them. An example, in this regard, is thc Mahakandarawa Reservoir in the Anuradhapura District. Hcre, the expected inflow to the reservoir is not received owing to the catchme~lt area being already exploited by a large number of village tanks that have been constructed or improved without any overall planning or coordination. Often this has been done on an ad-hoc basis, without the authorization of the Government organizations responsible for the Mahakandarawa Reservoir scheme. Thus, the cultivators for whom the Mahakandarawa scheme was developed, suffer from severe water shortages. The crux of the problem is that the Irrigation Department, which is responsible for the Mahakandarawa Scheme, does not have

the required authority to stop village tank improvement works w it11 in the catchment area which may be undertaken by other organizations. Steps should be taken to prevent the recurrence of similar situations.

(5) Existing provisions under the National Environmental Act prohibit- ing the discharge of factory emuents to rivers and waterways of the country without proper treatment should be enforced.

(6) With the expansion of urban systems the pollution of' urban water. bodics like Kandy and Nuwara Eliya lakes and associated drainagc canals has increased. This problem may assume scric;us propo~.tio~~s in the near future, unless early preventive measures are u nde~.talten.

A Water Resources Management Council when established, should be able to address most of the issues mentioned above. It is encouraging to note that the Ministries of Lands, Irrigatiofi, Forestry and Mahaweli Development and the Ministry of Finance and Planning are now taking necessary action in this direction.

A project on Institutional Strengthening for comprehensive Water Resources Management, funded by the Asian Development Bank, cornrneilced in 1996. The project is executed by the National Planning Department, under the guidance of a newly formed Water Resources Council, supported by a \iVatcr. Resources Secretariat. The Action Plan of this project addresses the following broad areas of institutional strengthening:

: Develop a National Water Policy. : Draft a National Water Act and regulations and amend other water-related

legislation. Reorganize and strengthen the management of water sector organizations, and establish a permanent co-ordination mechanism for the water secto~..

!: Establish data and information systems to meet the needs of'water manngct- ment, policy and planning.

: V a c i l i t a t e maximum public awareness of and participation in Water Management Strategies.

'"stablish appropriate systems and procedures for comprehensive planning based on management of river basins.

WATER RESOURCES OF SRI LANKA

SELECT BlBLIOGRAPHY

1. Arumugam S. (1969). Water Resources of Ceylon: utilization and deuelop- ~neizt. Water Resources Board, Colombo.

2. hiyananda K. (1985). Developingtlze Mahaweli Gangaf2~1lp0werp0t~r~fial. Pr0f.R.H. Paul CommemorationLecture, Institution of Engineem, Colon7 ba.

3. Arulanantham J.T. (1985). Measurement of hydrometeorological pararn- tsters. In: Some aspects of water resources of Sri Lanka roitlz special ~.ef;,ru~tce to Izydrology fEds. C. M. Madduma Bandara & N. M. Navaratne). The National Committee of Sri Lanka for the International ~~drologicaf Pro- gramme, pp, 13-16.

4. Arulanantham J.T. (1985). Rainfall. In: Some aspects of water resources of Sri Lanka. witla special reference to lzydrology (Eds. C. M. Madduma Bandara & N.M.. Navaratne). The National Committee of Sri Lanka for the Internu- tional Hydrological Programme, pp. 24-30.

5. Basnayake B.K. (1985). Evapotranspiration. In: Some aspects of' wc~fct. ~*c.sor~rces of' S1.i Lartka with special reference to lzydrology (Eds. C.M- Madduma Bandara & N.M. Navaratne). The Matianal Committee of'S1.i Lanka for the International Hydrological Programme, pp. 44-58.

6 . Basnayake B.M.S.B. & Madduma Bandara C.M. (1985). Groundwater in hard rock areas : resources and challenges for development. In: Some aspects of water resources ofSri Lanka witlz special reference to hydrology (Eds. C.M. Madduma Bandara & N.M. Navaratne). The National Cammittcc of Sri Lanlca fbr the International Hydrological Programme, pp, 238-257.

7 . Cook E.K. (1953). Ceylon, itsgeograplzy, its resources and itspeople. Maemill-ltn .St Co., London.

8. de Alwis K.A. (ed). (1972-75). Handbook of the soils of Sri Lanka. Jo~~rrlal of the Soil Science Society of Ceylon, Vol. 2.

9. de Me1 I. D.T. & Sumanasekera P. (1973). Groundwater recharge a t Yala, Joitrnal of the National Science Council of Sri Lanka, Val. I .

10. Department of C ~ ~ l s u s and Statistics (1985). Statistical pocket houh of ' t l~e Democratic Socialist Republic of Sri Lanka.

108 PALITITA &IAh'CHAh'AYAIiE & C.M. !\clrtDDlJM.-i B,'r\hrlJ.AI~\

Dharmasena G.T. & Manc-hanayake P. (1985). Sources of hydrological data. In: Some aspects of water resoz~rces ofSri Lanka with special refirence to hydrology (Eds. C.M. Madduma Bandara & N.M. Navaratne). The National Committee o f Sri Lanka fbr the International Hydrological Programme, pp. 17-23.

Dharmasiri J.K., D11ar1nawardaileK.G. & deMcl1.D.T. (1985). G r o u n d ~ t i t c ~ ~ ~ recharge in Sri Lanka. In: Some aspects o f~uuter resorrrces o/'Sri Lcl~r/:r~ wi th special reference to izydrology (Eds. C.M. Maddum:~ Ba11dt~1.a & N.M. Navaratne) . The National Committee of Sri Lanka i'ur thcb International Hydrological Programme, pp. 204-226.

Dimantha S. & de Alwis K.A. (1985). On-farm water management for Sri Lanka. In: Some aspects of water resources of Sri Lanka witlz special reference to hydrology (Eds. C.M. Madduma Bandara & N.M. Navaratnc). The National Committee of Sri Lanka for the Internatioaal Hydrological Programme, pp. 271-306.

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