ecosystem based indigenous water management · ecosystem, which was mainly based on2 inter-related...
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Ecosystem based indigenous water management
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Dedicated to God “Kadawara”
(According to the Sinhalese tradition, King Dhatusena appointed a man named Kadawara to maintain the magnificent Kalawewa. One day there was a breach in the bund. In order to stop the breach, Kadawara placed himself in the breach until workers repair it. During the event, Kadawara died and became a god. Today Kadawara is considered to be guarding the reservoir as a god as he did while he was alive.)
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Preface This is a valuable and timely publication on a vitally important topic, at a critical time. Apart from the problem of micro water management for cultivation mostly of traditional rice - paddy, there is the issue of macro water management, water sharing, in many parts of the country. After the on-going conflict over ‘traditional homelands’ is resolved, an even more serious and difficult conflict over water may follow. The seeds of the conflict over water were sown many decades ago, as I have documented over the past four decades, from the mid and later 1960s when I was working at Uda Walawe. To write this Preface, I referred to the Sanmugam Arumugam Commemoration volume ‘Water for People and Nature’, compiled by the late Engineer S H C de Silva, sometime Additional Director-General of Irrigation, and other Irrigation engineers in 2003. Both the Preface by Dr Ray Wijewardena titled ‘Water and Soil Conservation Ecosystems of Sri Lanka’, and the Introduction by Dr C G Weeramantry titled ‘The Significance of Sri Lanka’s Ancient Water Conservation Ecosystems to Modern Environmental Law’ are most appropriate to the subject of “Ecosystem based indigenous water management”, and extracts from those two chapters are used here with the authors’ permission. Dr Ray Wijewardena wrote that he was of the opinion that:
“By referring to the subject as ‘Irrigation’ we were perpetuating a rather serious misnomer; one which has probably crippled the country for decades. My suggestion was that the appropriate title was Water Conservation, rather than Irrigation”.
Mr Arumugam was one of the few engineers in his time who appreciated water conservation as well as small tanks, whereas most others had condemned them as ‘inefficient’ (from a hydraulic engineering perspective). Dr Ray Wijewardena offered a comprehensive explanation for this, and in effect described ‘ecosystem based indigenous water management’ from his own personal experience:
“The British engineers before us may be forgiven for their misunderstanding and mis-appreciation of the true purpose and function of the small tanks, which were strategically distributed throughout the countryside of this humid-tropical nation, on account of its unique climatic characteristics of alternating heavy rainfall and severe drought….
“As one who has farmed for many years in our ‘dry zone’, - and later served with several of the International Agricultural Research Institutes - it came to my understanding that these tanks, and almost all of those in southern India, demonstrated a major component of some of the finest systems of water conservation ever developed... That they had been designed towards achieving that fragile objective of sustainability which factor had, by subsequent and similar misunderstanding, likewise eluded many major civilizations in centuries gone by…..
“The run-off retained by the small tanks, strategically positioned across each fold in the contour, thus provided stability to an otherwise fluctuating water-table in the single monsoon regions of the dry zone where they were located. They are, likewise but more sparsely, evident in the two-monsoon regions of the wet-zone, where reasonably careful management of soil-cover, could provide the infiltration necessary to hold water in the soil and sub-soil until the next rains. (Regrettably this practice too has been all but lost in the mistaken fervour to emulate - as dry farming - the open-field farming systems of the west!).
“In the single monsoon season of the dry zone however, a sustainable existence was just not possible without a stabilised water-table to support the dry-zone forest garden and tree-based farming of the sloping ‘haena’, and supplementary rice farming of the ‘purana
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vela’. This, latter, was wisely restricted to the LHG - Low Humic Gley - soils which have very low permeability. Further conservation of the rainfall was achieved in bunded fields, now flooded to help manage weeds. (Let us remember that rice is a temperate and introduced crop which has, however, adapted well to the vela in the tropics, but which has proven colossally wasteful of now critical water, when also farmed thus on the RBE - Reddish-Brown Earth – soils”.
“The small tank system was always a key component in the water-conservation systems of our heritage…. They were not sources for abuse and mis-management under the misnomer of ‘irrigation’..... They were complementary to the system of interconnected large reservoirs and channels in the ancient Rajarata”.
Judge Weeramantry, former Vice President of the World Court, The Hague, said:
“The Water Heritage of Sri Lanka is a topic of worldwide interest, which has not attracted the attention and research it deserves. I therefore welcome any attempt to further our understanding of this system, which informed opinion regards as one of the most sophisticated irrigation systems the world has seen.
“Scholars of the greatest eminence, such as Arnold Toynbee in his monumental Study of History, Joseph Needham in his path-breaking Science and Civilization in China, and Arthur C Clarke in his inspired visions of the role of technology in uplifting the human condition, have all spoken of this system as the summit of global excellence in this field. It has also been described in superlative terms by such varied observers as Andrew Carnegie and Emerson Tennent, Henry Parker and R L Brohier, while recent work on the irrigation systems of the world, such as Goldsmith and Hildyard’s Social and Environmental Effects of Large Dams, recall how foreign observers have marvelled at it …..
“I have endeavoured in the legal field to stress the value of the wisdom and experience to be gathered in this field from past experience in maintaining a balance between these two essential considerations - development and environmental protection - which both exert enormous pressure, tugging the planner and the practical engineer in opposite directions.
“Out of this conflict has arisen the concept of sustainable development which I have sought to advance in the field of international law in several of my judicial opinions. In particular, in the Gabcikovo - Nagymaros Project case between Hungary and Slovakia in relation to the harnessing of the waters of the Danube, I stressed this concept and sought to elevate it to the level of a binding principle of customary international law. I believe it is now accepted as such.
“In urging for it this special legal status, I drew attention to various irrigation systems across the world and to the irrigation system of Sri Lanka as an example par excellence of a scheme which substantially advanced the concept of development, and at the same time substantially protected the integrity of the environment.
“I stressed in that Opinion, the immense, but much neglected, value of ancient wisdom to modern law --- a wisdom which placed great emphasis on the harmony between humans and their environment, on the rights of future generations and on concepts of communal duty rather than individual rights. I am glad to see that these trends have been picked up at various centres such as McGill University’s Center for Sustainable Development, and are being actively developed and advanced through academic and practical studies.
“The topic of sustainable development has in fact assumed such importance that it was the subject of a summit of World Heads of State and of World Chief Justices held at Johannesburg in August 2002. In my keynote address to the Chief Justices, I stressed the value of ancient wisdom, citing again the example of Sri Lanka’s water heritage as an outstanding example of this wisdom.
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“What strikes me as being of particular importance in this field of study is the perception that our ancient irrigation system was not merely an achievement of technical engineering skills of a pre-eminent nature, but also of a holistic conception of the setting of that expertise within the framework of an overall ecosystem of water and soil conservation. One cannot lose sight of either of these fields of expertise in which our forefathers excelled”.
These authoritative statements by two eminent scholars, Dr Ray Wijewardena the engineer - scientist, and Dr C G Weeramantry the scientist – jurist, is a great encouragement to the three authors of this original publication, Kapila Peiris, Mahinsasa Narayana and Sanjeeva Wijesinghe. They have taken on the ‘conventional wisdom’ of western educated and western oriented irrigation engineers, who as John Kenneth Galbraith once said are constrained to follow the conventional wisdom of the establishment, whatever commonsense, or traditional wisdom, or even their consciences may say. There is tremendous scope to build on this modest beginning. This little book has only touched the tip of the iceberg as the saying goes. It should be translated into Sinhala and Tamil, without delay, and made available to farmers at grass roots level. There will then surely be a massive feedback in support of what has been documented. Others will also take courage to contribute to the cause of restoring our cultural and economic heritage on the lines outlined in this original study. There is no time to be lost. D L O Mendis
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Content
Page 1. Introduction
2. Background
3. Indigenous water management
4. Concepts, attitudes related to the sustainable-development
model (for ecosystems)
5. Structural features and practices of this ecosystem
6. Comparison of water management methods
7. Paddy cultivation and water management
8. Evolution and Development of Irrigation Eco-Systems in
Ancient Sri Lanka
9. Conclusions / Comments
10. References
11. Appendix I
12. Appendix II
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1. Introduction
The main objective of this book is to give a basic introduction about our indigenous water
management. Actually it can be described as ecosystem management. In this regard physical
structures, practices as well as cultural aspects (concepts, attitudes economic development
model etc) related to this ecosystem management will be briefly outlined.
Indigenous water-ecosystem management cannot be simplified only to its physical structures
and practices. Presently, the physical structures and practices are taken isolated from the
cultural aspects and then with the current governing economic development model, these have
little meaning. Therefore the intention of this little book is to introduce both of these aspects
of indigenous water ecosystem management in a holistic manner, and to come up with some
guidelines drawn from the “indigenous water ecosystem management” which could be
included in a current water policy or in a related manner to solve some of the problems related
to water (ecosystem) in today’s context.
2. Background
Sri Lankan history is deeply connected with its hydraulic civilization. Today this hydraulic
system is erroneously named as an irrigation system. Nevertheless according to most of the
authorities and scholars1 in this field this was a sustainable water – soil – flora - fauna – human
ecosystem, which was mainly based on2 inter-related reservoirs (small and medium scale tanks
(wewa)) and channels in Rajarata, vetiyas in Ruhuna, and on diversion anicuts (amuna) in
Mayarata (i.e. mainly the wet zone). The history of this ecosystem leads back to the 4th century
B.C. or earlier. Basawakkulama sometimes known as “Abhayawewa” was identified as the
most ancient Wewa, which was built by king Pandukabhaya.
Ancient kings had built major tanks and village tanks simultaneously. For an example king
Parakramabahu the great had constructed 165 dams, 3910 canals, 163 major tanks and 2376
village tanks during the last lap of Rajarata3.
The stability and sustainability of this ecosystem was due to its ability to store the water from
rainfall within the system for the benefit of the whole system. Unlike in modern irrigation
systems, which are focused on supplying the crop water requirement for the root-zone (zone in
soil where the roots of trees and plants are spread, water is absorbed by roots in this region), the
ancient so-called “hydraulic system” was focused on the water requirement of the entire
1 Eng. D L O Mendis, Dr Ray Wijewardena, Judge Dr C G Weeramantry 2 R L Brohier, 1934 3 S Arumugam, 1969
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ecosystem. To fulfil this requirement, various types of structures such as major tanks, small
tanks, vetiyas, amunas, vila (lake), wala (pond) etc. (Figure 1) and inter connecting canals were
constructed very much in harmony with nature.
In some areas water from major rivers was conveyed to the major tanks and from there to the
small tanks and then to the fields, for example Elahera – Parakkrama Sagaraya. In some other
areas this happened the other way round, i.e. water spilling out from small-tanks was stored in
major tanks; for example Kuluwewas, small surface storage consisting of earth bunds used as a
silt trap, and flow controller for flood mitigation, raising the water table in the vicinity, were
incorporated in most of the ancient systems. In almost all these cases small tanks were
constructed in a cascade system, which facilitated efficient re-use of water. In this manner
these structures were used to store water in the ecosystem (i.e. in the soil and vegetation) in
drought periods, and were used in flood mitigation in rainy periods. It should be mentioned here
that irrigation was only a part of this hydraulic system, which should be seen as a conservation
system or more correctly as a water and soil conservation ecosystem. Kalaweva – Jayaganga is
often thought to be the classic example where large reservoir, trans-basin canal, and cascades of
small village tanks formed a stable human-made ecosystem.
As mentioned earlier, the heart of this ecosystem was the wewa, which gave the lifeblood for
the ecosystem. These systems have been sustained for thousands of years. The sustainability
and stability of these ecosystems is not only due to their physical structures mentioned earlier.
The culture that prevailed in these regions also provided necessary conditions for this
sustainability. As Pffafenberger said4: “a more useful definition of trechnology would certainly
include cultural values and social behaviour”. This culture can be assumed to be driven not by
the self-interest motivated by greed, but by other motivations like group interest (discussed
under 5.0 Water distribution), and sharing resources equally (even among animals, birds etc.)
and the equity of ownership. Arahat Mahinda when he preached the first sermon on sustainable
development at Mihintale in 223 BC5 stated that the king was only the guardian of nature and
not the owner. Keeping a Kurulupaluwa (portion of paddy field reserved for birds, that exists to
this day) was a direct outcome of this concept. This culture with the concept that we are just
guardians of nature, and the physical structures like wewa served this ecosystem, made it
possible for it to function for thousands of years. Thus this culture-ecosystem had the in-built
development model that is suitable for our environment and culture. Now we are going away
4 Pffafenberger, 1990 5 Judge C G Weeramantry (1997) Separate Opinion in the Danube dam case in the World Court, The Hague
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from this tradition. Today we do not have an idea about our former development model and
therefore we cannot rehabilitate these ecosystems in a sustainable manner.
This has been observed by Judge Dr C G Weeramantry former Vice-President of the World
Court, The Hague, and by Judge Dr A R B Amerasinghe6 in the Supreme Court of Sri Lanka.
Judge Weeramantry said:7 “our ancient irrigation system was not merely an achievement of
technical engineering skills of a pre-eminent nature, but also of a holistic conception of the
setting of that expertise within the framework of an overall ecosystem of water and soil
conservation”. Justice Amerasinghe8 said “The Jayaganga …. is not merely a water course or
transportation canal corridor, or even an amazing technological feat as Professor K M de Silva
describes it; it is also an integral part of a human-made water and soil conservation ecosystem”.
It should be mentioned here that although we cannot go back to the same system today, the
guiding principles provide important guidelines for a modern day sustainable water
management policy.
3. Indigenous water management
In the ancient cultural context water management was not taken as an isolated issue. Here the
main objective of water management is to optimize the conditions for the proper function of the
human – made ecosystem in harmony with nature. Water was mainly stored in the wevas and in
the soil and conveyed through the soil, and the soil facilitated mainly the water purification
process. Water is taken from the soil (from the water table) then the used water is again
returned to the soil, which purifies the water and replenishes the water table for re-use. Water
was thus conserved in the soil, maintaining the water table. To facilitate this conservation,
physical structures like cascade wewa system in Rajarata, vetiyas in southern area, and amunas
were built according to the geophysical nature of the location. In this manner water received
from the two monsoons was re-used several times before it ultimately drained to the sea. Even
the inter-monsoon rains (Akvehi) would have facilitated this re-use process (i.e. cyclicity). The
water evaporated from the wewas help to create convection rains (Akvehi)9. Hence evaporation
from wewas is not a real loss! Also these structures facilitated flood mitigation process in the
lower parts of the ecosystem in heavy rainy periods. In this context ecosystem is defined even
including the man and the objects and the accessories required by him for his livelihood10.
6 Dr A R B Amerasinghe. (2000) Eppawala FR case SC Application No. 884/99, 2 June 2000 7 Preface in Water for People and Nature, Sanmugam Arumugam Commemoration. 2003, Vishwa Lekha 8 Reference 6, Eppawala FR case Judgement. 9 Farmers in villagers such as Puleliya, say this by looking at the directional movements of the clouds. When the clouds are almost stationary, they identify the rains as Akvehi 10 E P Odum, (1982)
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4. Concepts, attitudes related to the sustainable-development model (for ecosystems)
From the time of the first sermon at Mihintale by Arahant Mahinda to King Devanampriya
Tissa (c. 223 BC), Buddhism has significantly influenced the Sri Lankan life style (e.g.
attitudes, concepts). Some prominent Buddhist concepts are listed below.
1. Greed (Thanha) is the cause for sorrow Dukha. Therefore it should be mitigated11.
2. Happiness is the most important wealth. (“Santhutti paramang Dhanang”)12
3. Equity of ownership.
4. Attitude towards nature - nature does not belong to anybody. We are only a part of it and
we can use it in a sustainable manner for our survival without disturbing much its use by
the other partners. Statement of Arahant Mahinda.
5. Less selfish, holistic community based approach to optimise the ecosystem.
6. Holistic approach towards nature13
5. Structural features and practices of this ecosystem
5.1 Rain water trapping structures
In the ancient water management, the amount of rainfall (nowadays measured in “mm”) and the
intensity of rainfall (nowadays measured in “mm/day”) were deliberated.
Small structures like Vetiya capture the water from very low intensity rainfall. Small tanks
capture the water from much higher rainfall and major tanks capture water from even higher
rainfall14.
11 Buddhist Sutrapitake – Lord Buddha 12 Buddhist Sutrapitake – Lord Buddha 13 Dr P B Dharmasena, Deputy Director, Field Crops Research Institute, Maha Illupallama 14 Dr C R Panabokke (2001)
Figure 2: Vetiya in southern region (from Walawe Engineering surveys)
Wala (pond)
Wila (lake)
Wewa
Wetiya
Figure 1: Rainwater trapping structures
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5.1.1 Wewa
There are about 12,000 working small tanks and anicuts in Sri Lanka which irrigate an extent of
about 185,000ha. This is 35% of the total irrigable area in the country. Small irrigation schemes
produce 191,000 metric tons annually accounting for 20% of the national irrigated rice
production15. Following are the essential components of a village tank (Figure 3).
Gasgommana – It is the upstream of the land strip located above the tank bed and water is
accumulated in Gasgommana only when the tank spills. Naturally grown large trees such as
Kumbuk, Nabada, Maila, Damba etc. and climbers such as Kaila, Elipaththa, Kakukeliya,
kalawel, bokalawel etc. are found in this area. The gasgommana acts as a wind barrier and at
the same time it helps to reduce evaporation from the tank and to lower the water temperature.
It gets closer to the bund from either side where roots of large trees make water cages creating
breeding and living places for some fish species. This strip of trees demarcates the territory
between human and wild animals.
Perahana – It is the meadow developed under gasgommana and filters the sediment flow
coming from the upstream chena lands.
Iswetiya or potawetiya – It is the soil ridge constructed in the upstream of the tank at either side
of the tank bund to prevent the eroded soil from upper land slopes from entering the tank.
Godawala – A manmade water hole to trap sediment and it provides water for wild animals.
This might be a strategy used to avoid man-animal conflict.
Kuluwewa – A small tank constructed above the relatively large reservoirs only to trap sediment
and not for irrigation purposes, as seen above Minneriya weva for example16. It provides the
water necessary for cattle and wild animals.
Tisbambe – It is a fertile land strip found around the settlement area (gangoda) and does not
belong to any body. Tree species such as mee, mango, coconut etc. are grown in scattered
manner. Mostly this area was used for sanitation purposes and it acts as the resting place of
buffaloes. Buffaloes were used as a protection mechanism from wild animals and malaria.
Kiul ela – This is the old natural stream utilized as the common drainage. Tree species such as
karanda, mee, mat grass, ikiri, vetakeya etc. and few rare small fish species are also found in
water holes along the kiul ela. Most importantly it removes salts and iron in polluted water and
improves condition of the drainage water from the paddy tract.
Kattakaduwa – This is a reserved land below the tank bund. It consists of three micro-climatic
environments: water hole; wetland; and dry upland, therefore, diverse vegetation is developed.
15 Agricultural implementation programme 1994 - 95 16 Udula Bandara Avusadahami, 2000. Weva
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This land prevents salts and ferric ions entering into the paddy field. The water hole referred to
as ‘Yathuruwala’ minimizes bund seepage by raising the groundwater table. Villagers plant
vetakeya along the toe of the bund to strengthen stability of the bund. It appears to be the
village garden, where people utilize various parts of the vegetation for purposes such as fuel
wood, medicine, timber, fencing materials, household and farm implements, food, fruits,
vegetables etc17. Specifically they harvest raw materials from this vegetation for cottage
industries.
Figure 3: Essential components of a village tank (Dharmasena, 2000)
5.1.2 Cascade system
A connected series of tanks are organized within the micro catchments of the dry zone land
escape, for storing conveying and utilising water from an ephemeral rivulet (Madduma Bandara
1985).
Figure 4: Functional diagram of a cascade system (Dharmasena, 2000)
17 Dr P B Dharmasena, 2000.
Chena
Perahana
Godawala
Tank Iswetiya
Landa Paddy field
Kiulela thisbambe
gangoda
Chena
kattakaduwa
Gasgommanana
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It is now clearly recognized that the large number (more than 15,000) of small tanks that are
distributed across the undulating landscape of the dry zone are not randomly located and
distributed as previously commonly perceived; rather they are found to occur in the form of
distinct cascades that are positioned within well defined small watersheds or meso-catchment
basins. A cascade of tanks is made up of 4 to 10 individual small tanks, with each tank having
its own micro-catchment, but where all the tanks are situated within a single meso-catchment
basin. These meso-catchment basins could vary in extent from 6 to10 sq.miles, with an
optimum value of about 8 sq. miles in the North Central Province region.
Figure 5: Schematic representation of small tank cascade (Panabokke, 2000)
A schematic representation of a typical small tank cascade system with a scale of 1:50,000 is
shown in Figure 5. The main elements to make up a cascade are namely; (a) the water shed
boundary of the meso-catchment, (b) the individual micro-catchment boundaries of the small
tanks, (c) the main central valley, (d) side valleys, (e) axis of the main valley, and (f) the
component small tanks as well as the irrigated rice lands as shown in the same diagram.
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These small tanks form a series of successive water bodies along small water courses and are
called a “cascading system’’. The advantage of such a system is that excess water from a
reservoir along with the water used in its command area is captured by the next downstream
reservoir, and is thus put to use again in the command area of the second reservoir. This water
is thus continuously recycled. This system helps to surmount irregularly distributed rainfall,
non-availability of large catchment areas and the difficulty of constructing large reservoirs18.
In Rajarata these cascades are very much related to the topography of the underlying bedrock.
Most of the cascades are situated above the ‘basins’ in the bedrock, and this would have
minimized the ground water outflow from the system. In Ruhuna area the underlying bedrock
slopes towards the sea, and this would have been one main reason why there are very few
cascades of small tanks in the area. In Ruhuna a structure known as ‘vetiya’ (Fig. 2) is used to
conserve water in upper portion of the soil19.
5.2 Sharing outcomes of ecosystem but not raw resources
The outcomes of the ecosystems (paddy, other crops, water etc.), which are needed for the
human livelihood, are shared among the people in the ecosystem. The ecosystem does not
belong to or owned by anybody. The ecosystem is virtually not divided among people instead
outcomes are shared. Dividing the system for individual ownership beyond a limit will disturb
the system. “Bethma” and “Thattumaru” methods of cultivations are adopted to avoid this.
5.3 Bethma method of cultivation
In water scare situations, villagers get together and agree on an area, which could be cultivated
with the limited water available. Later, the harvest (paddy) is divided among them.
5.4 Thattumaru method
This method is adopted by villagers, when the fragmentation of lands makes it difficult to
cultivate in small individual units. When a villager has a small unit, he opts to forego the
cultivation of his unit giving the opportunity for another to cultivate a larger unit including his.
This makes the operational unit more viable. Each farmer gets his turn although not every
season.
5.5 Water distribution
Traditionally a holistic approach was used for water distribution in the irrigable area, according
to community or group interest, rather than individual self interest as seen in modern schemes. 18 Panabokke (2000) 19 Prabath Vitharana, Department of Agrarian Services
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The colonial lawyer F A Hayley in his book on Kandyan Law wrote:
“The irrigating stream, passes from one allotment to another, arranged, when possible, in a
series of terraces, in each of which the supply and depth is regulated by low ridges and
blinds, temporarily breached or dammed as occasion may require. The regulation of this
supply, the formation of the enclosing ridges, the joint use of buffaloes for ploughing, and the
need of fencing against wild animals, necessitate community of action on the part of tenants
of adjoining lands …
“To produce a successful crop, organization is required, some panguwas needing, from the
nature of the soil or elevation, treatment different from the others. For this purpose, the
tenants appoint their own official, the vel vidane or irrigation headman ... .
“It will be convenient here to refer to the social and administrative organization: for while the
lord of the village, or the chief or headman, to whose control it was assigned, was primarily
responsible for good order, there existed side by side with community of property, a
community of responsibility, and a recognition of self-government by the village council in
the regulation of local affairs ". (Hayley, 1990, pages 261-266, Village Communities)
Thus, the indigenous method is a bottom-up system of water management while the modern
method is a top-down system (Fig. 6). This is specially important when considering devolution
of administrative authority from the Centre to the regions that is being discussed today.
Indigenous system Modern system (Source: Brohier, 1941) (Source: Irrigation department)
Fire 6: Water distribution
Figure 6: Water distribution methods (Mendis, 2002, p. xxii)
Each farmer (plot) has a supply and outlet (drainage) separately
Water was supplied to the field in a holistic manner drainage from upper fields are used in lower fields (re-use)
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5.5.1 Bisokotuwa
Biskotuwa20 is a device invented by ancient engineers to control the outflow of water from
wewa with considerable heights (10-15m). As shown in Figures 7, 8, 9 below, the Bisokotuwa
consists of a tank, rectangular in plan, connected to the sluice barrel or conduit; in almost all the
cases the longer side of the rectangle is kept parallel to the bund. Little real evidence regarding
the gates of the Bisokotuwa has been found up to now, although Brohier mentions a stone gate
in a sluice at Mahavillachchiya. (Brohier 1934, Vol. II). Speculation about gates, which would
have been made out of wood and controlled by a system of levers, are mostly accepted in the
present day among scholars. With these speculations about gates, the function of the
Bisokotuwa could be explained as follows (Figure 7):
When it is required to release water from the wewa, gate A is opened gradually while B is kept
open at a particular opening (or gate B would not have existed); then the water level in the
Bisokotuwa will come to a height less than that of the water level in the wewa. Then water will
flow through the sluice to the outside canal driven by the head of water in the Bisokotuwa,
without subjecting the sluice barrel or conduit in the bund to high pressure as well as velocities
created directly from the head of water in the wewa. When stopping the water release from the
wewa, gate A is closed then water inside the Bisokotuwa will flow through the sluice barrel,
without creating any vacuum condition. In this manner the Bisokotuwa acts as a ‘surge’ tank,
but this is not simply a ‘surge’ tank; if this was only a surge tank such large cross-sections such
as 11x8 feet, 10x9 feet etc. are not needed.
5.5.2 Analysing Bisokotuwa as a Flow Regulator and a Meter Using Modern Hydraulics
Figure 7: Schematic diagram of Bisokotuwa
20 Parker, H (1908) “Sinhalese engineers invented the bisokotuwa in the 3rd century BC”.
Gates
Bisokotuwa
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Applying Bernouli’s equation to Bisokotuwa :
from A to B
H-h = f1 (Q, a1) _______ (1)
from B to C
h = f2 (Q, a2) _______ (2)
Where
H = Height of water in vewa
h = Height of water in Bisokotuwa
Q = Water Flow Rate
a1 = Opening area of gate G1
a2 = Opening area of gate G2
From equation (2) it is clear that for a particular set of values of a2 and h, Q will have a fixed
value. Now, the Bisokotuwa can be calibrated by finding the Q values for various sets of a2
and h i.e. determining the two variable function “f2 now if we want to have some particular Q
value then we have to find the two values of a2 and h accordingly and open the gate “G2”.
Now open the gate “G1” such that the water level inside the Bisokotuwa will be equal to above
“h” value. Then the required water flow “Q” will take place. When the water level in the vewa
goes down “h” will also go down. Then by increasing the opening area of gate “G1” “h” could
be brought to the initial value i.e. the water flow rate from the vewa could be kept constant
independent of the height of the water level in the vewa (for a particular range). Also once the
Bisokotuwa is calibrated as stated said above it could be used to measure the flow rate, i.e.
when “h” and ‘a2” are known ‘Q” can be determined by calibration charts or graphs.
When water is going out from the wewa, the water first enters the Bisokotuwa, the head of
water entering it is decreased by allowing it to expand in it. Bisokotuwa is an effective
expansion tank. This may probably be the reason for laying out the Bisokotuwa so that its
longer side is parallel to the bund i.e perpendicular to the sluice barrel or conduit, the direction
of water flow. In the Bisokotuwa the flow (and pressure) of water issuing from wewas with
high heads are controlled by dissipating energy in the water by letting it expand in the
Bisokotuwa or rather by allowing the water coming in to the Bisokotuwa to impact with water
inside the Bisokotuwa, thereby releasing its energy by an ingenious non-destructive method.
For this to take place properly, the volume of water inside the Bisokotuwa is of critical
importance. The large cross section of the Bisokotuwa stated above will fulfil this
requirement. The Bisokotuwa was described as the fore-runner of the modern valve pit or valve
tower by Parker (Ancient Ceylon), but such large cross sections are meaningless if this was
12
only a valve-pit. In some wewas, for example Urusita wewa at Sooriyawewa, (Figure 8) water
enters the Bisokotuwa by one conduit (sluice barrel) at the bottom center and goes out by two
conduits from the bottom of the opposite wall. With this arrangement the effect of momentum
of inlet water on outlet water will be minimized, i.e the outflow will be very calm. Also
velocity of water in the outlets will be lower than that of the inlet. Higher velocity in the inlet
will increase energy loss; low velocity in the outlets will give a gentle flow, which will not be
harmful to the bund as well as to the downstream channel.
The Bisokotuwa is also used to change direction of water flows. One such example is seen at an
outlet in Parakrama Samudra (Figure 9). In this case, water enters the Bisokotuwa from one side
and leaves it from a side perpendicular to it. The forces required to divert the flow of water is
obtained from the water itself (inside the Bisokotuwa). Therefore, no such effects as erosion of
conduits can take place.
5.5.3 Planked arrangements inside a bisokotuwa
According to Professor R.A.L H. Gunawardena (‘The ancient sluice at Maduruoya reservoir’),
Bisokotuwa of another type also has existed. In this type wooden panels were used to control
the water (Figure 11). These wooden panels were inserted parallel to the bund in a structure
which had grooves. With the wooden panels the bisokotuwa is actually divided into two parts.
Figure. 9: Water diversion at Parakrama samudra (plan)
Figure.10: Water diversion Bisokotuwa at Parakrama Samudra
Figure. 8: Bisokotuwa at Urusita weva
13
The level of water in the upstream side of the Bisokotuwa will be almost the same as in the
wewa. When the uppermost panels are removed water will flow into the downstream side of
the bisokotuwa and will then flow through the sluice conduit in the bund very gently.
Figure 11. Sketch of planked arrangements inside bisokotuwa
In this method water outflow (volumetric flow rate) could be controlled very easily and
independently of the water level in the wewa. Also because only the uppermost panels are
removed (or inserted) forces involved in removing (or inserting) will be less due to low
pressure. This is very similar to a “ketasoruwwa” (Figures 12, 13). Also this is very similar to
the principle of a planked anicut. Even very recently (about 30 years ago) at Ratmalgahawewa
in Anuradhapura, wooden panels inside the bisokotuwa were used to control outflow of water.
5.5.4 Navigation in canals with the aid of locks
A similar technique had been used to facilitate navigation along waterways at different levels
in ancient times. Elahera – Minneriya canal was restored by Parakrama Bahu (1153 – 1186)
using locks despite 60 ft. difference in level between Elahera and Minneriya. He built
Parakrama Sagara by raising Elahera anicut built by Vasabha ( 65 – 109 AC), creating
Koththabadhdhanijjara, described by Geiger as the “reservoir whose flood escape was walled
up” and also as the “weir furnished with a reservoir” (Mendis, 2002). Parakrama Sagara, the
second “Sea of Parakrama” was discovered by three British surveyors in 1855, and their report
was published by Governor Sir Henry Ward, in his Minutes in 1867. (Brohier 1934, Vol. 1 pp.
Dam Vewa
Keta
Figure. 12: Keta sorrowwa
Figure. 13: Keta sorrowwa, Puleliya
Wooden planks GrooveDAM
WEVABISOKOTUWA
14
28-32) An ancient tamarind tree to which boats were anchored had been found, and the stump
of this tree is now the site of a small shrine on the Elahera canal bund. The Surveyors report
re-published by R L Broher was ignored by engineers when the Elahera canal was restored
during world war II, (Brohier, 1941) and also later when Moragahakande reservoir and the
NCP canal was proposed. (Mendis, 2002)
Figure 14: Ancient bisokotuwa at Maduruoya
5.5.5 Ancient bisokotuwa at Maduruoya
Ruins of a basement, which could be considered as a basement of a structure, which carried the
relevant grooves, is found at Maduru oya old sluice (Figure 14), which consists of an almost
rectangular dressed stone sluice barrel or conduit backed by brickwork and a triangular brick
arch above the conduit, and these bricks do not show any wear due to water flow (Figures 15).
Therefore it could be concluded that this upper part of the sluice was not used to convey water
instead it would have been a free passage to prevent water flowing in the sluice conduit below,
making contact with the bund. Due to this arrangement even when pressure inside the stone
sluice increased and water flowed through it was unlikely to seep into the bund.
Figure 15: Ancient sluice at Maduruoya
15
5.5.6 Karahana
This device provides an even more simple distribution method in the downstream irrigated area,
when compared with modern methods. Once a certain amount of water is released from the
wewa each and every plot will get an approximately equal amount of water. Nobody is needed
to regulate water from plot to plot.
Figure 18 -Water dividing devices (Karahana) used in channels in Pul Eliya
Karahana
21
22
.ll
lQQ+
=&
&21
11
.lllQQ
+=
&&
Figure 16: Schematic diagram showing the function of Karahana
Figure 17: Picture of the Karahana at Pul Eliya village (Leach, 1967)
16
5.6 “Rajakariya”
A community based maintenance methodology for the ecosystem. In this method, about 40 days
of each year villagers worked for the benefit of the whole community (ecosystem).
5.7 Trans-basin canals developed within the ecosystems
With a holistic approach, in-situ time tested irrigation and water supply projects developed
gradually. For example Kalaweva - Jaya Ganga ecosystem was described by Brohier (1937):
“The Jayaganga, indeed an ingenious memorial of ancient irrigation, which was undoubtedly
designed to serve as a combined irrigation and water supply canal, was not entirely dependent
on its feeder reservoir, Kalaweva, for the water it carried. The length of the bund between
Kalaweva and Anuradhapura intercepted all the drainage from the high ground to the east
which otherwise would have run to waste. Thus the Jayaganga adapted itself to a wide field of
irrigation by feeding little village tanks in each subsidiary valley, which lay below its bund.
Not infrequently it fed a chain of village tanks down these valleys the tank lower down
receiving overflow from the tank higher up on each chain".
Another example is Parakrama Sagaraya, which has been described thus:
“King Vasabha (65-109) built the Elahera anicut and canal in the first century; nearly three
centuries later King Mahasen (276-303) built the Minneriya weva at the tail end of the canal,
and probably started its extension beyond Minneriya. Later kings, up to Aggabodhi I, (575-
608) completed the extension, and Aggabodhi II (606 - 618) built the Gantalawa weva
(Kantale tank) at the tail end. Beyond Kantale Weva, channels led to Tambalakamam bay and
the sea at Trincomalee.
“This system functioned in the next nearly six centuries, until the reign of Parakrama Bahu
(1153-1186), who restored and greatly improved the system. This king raised the Elahera
anicut, and strengthened the first 24 miles of the canal from Elahera to Konduruweva, thus
creating the second Sea of Parakrama, or Parakrama Sagara, described in the Culavamsa as
Koththabadhdhanijjara. This Pali word was translated by Geiger in two different ways which
have the same meaning as it should namely ‘the weir furnished with a reservoir’, and ‘the
reservoir whose flood escape was walled up’ ". (Mendis (2002).
Actually these are not canals in the modern sense. They consist of earthworks (bunds), which
divert the free flow of water slightly in order to collect water from excess-water areas and then
distribute them to water-scarce areas as in the Jayaganga described by Brohier. Therefore it is not
quite correct to express the gradients of such “canals” in the context of modern channels which are
17
meant to convey water from one point to another as quickly as possible. In most cases these old
channels follow a gently falling contour, and have only a single bund equipped with spillways. In
fact, Parakrama Talaka, the third “Sea of Parakrama” may have been formed by accumulation of
water along part of the contour channel of the Kalaweva Jayaganga as described by Brohier.
5.8 Diverting water from rivers
When diverting water from rivers, ancient ‘engineer’ has never ‘silenced’ the river (McCully,
1996). i.e. the natural river flow has not been stopped totally, instead a part of water has been
diverted without seriously affecting the downstream side of the river and also without creating a
large reservoir. In most cases, these goals were achieved by constructing oblique dams or weirs
(In some cases temporary wooden dams or weirs). Also in some cases these dams or weirs were
not built totally across the river. When the weir is built obliquely it could transfer (overflow)
much water flow without increasing the height of water above the weir. Therefore oblique weirs
provide a method to divert a small amount of water flow without significantly increasing the
water level above the weir which will otherwise make a deep large reservoir.
In almost all the cases water has been diverted from regions where the silt accumulation is
lowest (i.e. in most cases from the outward side of a bend). In ancient times water from water
excess areas were first taken into the nearest water scarce areas, then the remainder to the
immediate next and so on. Therefore elevating water for higher levels was not required, as in
modern lift irrigation projects introduced by transfer of technology.
5.9 Using the behaviour of water to take levels
Most of the ancient water systems, which now appear to be very large, were not done in short
time intervals as today. Actually these have evolved in stages (e.g. Jaya Ganga and Parakkrama
Sagaraya, in ancient Rajarata). Hence it is quite reasonable to assume that level measurements
related to these works would have also been taken along with the work while observing the
natural flow of water. Anyway there would have been simple devices, which could be used for
taking level measurements. Such a simple wooden device is shown in Figure 20.
Figure 19: indigenous levelling devices
Wooden frame
The bottom plane and plane ABC are parallel. By poring water to this vessel it is possible to take levels
18
Even today if we consider the formation of paddy fields (especially in wet zone) one can
observe large areas of levelled paddy fields. This levelling is achieved by observing the free
water flow and carrying out earthwork accordingly. No instruments as such are used!
6. Comparison of water management methods
Comparison of water movement-circulation in a typical indigenous ecosystem and water
distribution-drainage system in a typical modern system is illustrated as follows (A proper study
has to be carried out for more details).
6.1 Indigenous (traditional) ecosystem
This is the Ecosystems perspective, which is based on the sustainable development of human
and environment within the context of Sri Lankan culture. Water received as rain is stored in
the ecosystem in a usable manner then used and re-used as drainage is again fed to the system
and reused several times. Cause and effect of this is as follows:
• Small water cycles through soil: Water cycle is connected with soil in local vicinity.
• Water purification is mainly done by the soil.
• Whole land area is irrigated together so that water is conserved, conveyed through the soil
or unlined canals.
• Evaporation (specially from wewa) facilitates local water cycles and gives rise to
convectional rain (Akvehi)
• People live along the cascade, thus facilitating reuse of water
6.2 Modern system
The modern system is based on the hydraulic engineering storage tank perspective. Water
gained from rain is stored in tanks, then used and excess is treated as drainage. Water cycle is
largely connected with the sea or other reservoirs, mainly through pipeline or concrete canals
(i.e. water supply and drainage).
• Water cycle is less connected with the soil, people and nature, in local vicinity
• Less water purification by the soil (pollution is also high)
• Less water re-use
Today with urbanization connection of water with soil is reduced. Individuals suck water from
wells (from water table) and store them in overhead tanks. These will deplete the water table
then in most areas the used water is send to sea through drains without much contact with the
soil. Therefore the cyclicity of water through soil is disturbed and this will give rise to water
shortages, in the region. Also for towns water is pumped from rivers and other sources, no reuse
as in a village wewa. Population is clustered in towns unlike in cascade irrigation systems.
19
Today in most development projects canals are constructed for irrigation purposes and separate
pipelines are laid for domestic purposes. In ancient systems irrigation as well as other purposes
were fulfilled by the same water system, with people very much closer to nature and with very
much less water pollution. In fact Mahamankadavala Piyarathana Thera of Galkande Purana
Maha Vihare, Eppawala, said that about 30 years ago they drank the water from the canals, but
now with introduction of chemicals the water system has been polluted and separate water
sources are needed for human consumption.
7. Paddy cultivation and water management
Paddy cultivation is highly connected with water management in Sri Lanka. Almost all the
recent irrigation development projects were aimed at supply water for paddy fields. Anyway it
must be mentioned here that the actual crop water requirement of paddy and the amount of
water used for paddy cultivation in conventional paddy cultivation systems (in paddy fields) are
different. Water in conventional paddy field systems caters for many requirements of the
ecosystem.
Specially wet zone paddy fields acts somewhat like small wewas. Rainfall water, which could
easily drain to sea, is stored in these fields. Also these acts as sponges during heavy rains and
are a buffer against erosion. They develop the water table in the vicinity providing water to the
ecosystem.
Figure. 20: This is not only irrigated paddy cultivation but also conserving water for the ecosystem
According to Dr. Ray Wijewardene, in the single monsoon season of the dry zone, a sustainable
existence was just not possible without a stabilised water-table to support the dry zone forest
garden and tree-based farming of the sloping “haena”, and supplementary rice-farming of the
“purana-vela”. This latter was wisely restricted to the LHG (Low Humic Gley) soils, which
have very low permeability. Further conservation of the rainfall was achieved in “bunded
fields”. Paddy, a plant, which could withstand flood condition was grown in these “wewas”.
20
Therefore one cannot directly say that all the water in paddy fields are a requirement of paddy,
and paddy is a crop, which “wastes” water. Proper studies have to be carried out on this matter,
based on the ecosystems perspective. To facilitate such study, contrasting features of the
hydraulic engineering and ecosystems perspectives are listed as follows (Mendis, 1986):
Hydraulic Engineering vs. Water and Soil Conservation Ecosystems Hydraulic engineering
(Hard technology/Transferred knowledge)Ecosystems perspective (Soft technology/Traditional knowledge
1. Water inanimate, active animate, passive
2. Small tank “inefficient” stage in evolutiondevelopment - to be replaced by large reservoir
micro-irrigation ecosystem - essential part of total complex of human-made ecosystems
3. Large reservoir “efficient” system in combination with channel distribution irrigation system
macro-irrigation ecosystem with micro-irrigation ecosystems in its command area
4. Diversion Channel built to augment a large reservoir - last stage in irrigated agriculture system
earliest stage in irrigated agriculture
and evolution of ecosystems
5. Vetiya “abandoned small tank” deflection structure - micro water and soil conservation ecosystem
6. Downstream development areas
must be cleared of all vegetation to lay out channel distribution irrigation systems
designed as a series of micro water and soil conservation ecosystems
7. Forest areas limited to catchment areas not only in catchment areas - inter- spersed with fields in development areas for better nutrient flows
It is worthwhile to quote the following on “rice paddy ecosystems” in Bali by Steve Lansing21
(1991) because it would be very helpful in understanding our ancient paddy ecosystem also.
“The role of water in rice paddy ecosystem goes for beyond providing water to the roots of
paddy plants. By controlling the flow of water into terraced fields, the farmers are able to
create pulses in several important cycles. The cycle of wet and dry phases alters soil pH;
include a cycle of aerobic and anaerobic conditions in the soil that determines activity of
micro-organisms, circulates micro-nutrients; fosters the growth of nitrogen- fixing cyan
bacteria; excludes weeds; stabilizes soil temperatures; and over the long term governs
formation of a plough pan that prevents nutrients from being leached into the subsoil. On a
larger scale the flooding and draining of blocks and terraces also has important effects on
pest populations. If farmers on adjacent fields can synchronize their cropping patterns over a
sufficiently large area, rice pests are temporarily developed of their habitat and pest
populations can be sharply reduced.” 21 Lansing. 1991
21
7. Evolutions and Development of Irrigation Eco-Systems in Ancient Sri Lanka
(Mendis, 1986)
1. Rain – fed agriculture
2. River diversion from a flowing river (ganga oya, ara etc.) Temporary or seasonal diversion structures made of sticks and stones etc. on poor foundations
3. Development of permanent river diversion structuresDevelopment of dressed stone masonry, including wedge shaped blocks, use of lime mortar etc. on good foundations
4. Construction and operation of spillways and weirs Along contour channels, using dressed stone masonry, natural rock ourcrops etc.
5. Invention of the sluice (sorowwa), with access tower (bisokotuwa) – precursor of the modern valve tower
6. Construction of small, medium and large storage reservoirs across non-perennial oyas and aras, and in so-called dry valleys, using the sorowwa with bisokotuwa for controlled issue of irrigation water, and the spillway for safe discharge of flood runoff
7. Damming a perennial river Two techniques were available for damming a river that had some flow, however small, even in the driest season:
i. Temporary river diversion through a sluice ii. The twin – tank method
Diversion channels for flood irrigation on riverbanks
Development of contour channels
22
Figure. 21: Temporary stick dam at Kalahagala - An example of stage 2 in above.
9. Conclusions / Comments
Water management cannot be identified as an isolated issue. It is intimately related to the
national economic development model related activities, physical structures, practices,
concepts, and attitudes in the related culture. A basic introduction about these interrelated
categories in modern and ancient contexts is given in this report. Therefore in addressing water
related issues one should base it on this threefold approach.
(a). Today in the process of solving the water shortage problems one should first study the
methods and ways of improving the cyclicity of water through nature separately for each
geophysical situation. Conserving water in soil must be considered first i.e. water table
should be uplifted. In “hydraulic” water works only rainfall data from isohyets and
topography of catchments are taken into consideration. Cyclicity of water through soil (as
well as through vegetation and atmosphere) is ignored. Evaporation from tanks (wewa)
and seepage are taken as losses!
Economic development model- related activities
Physical structures- practices
Concepts-attitudes in the related culture
23
Also instead of net rainfall, rainfall intensity (mm/day) has to be taken into account22.
Rainfall intensity has a direct bearing on the distribution of water in soil, therefore by
considering this fact proper structures such as Vetiya, wewa has to be constructed in order
to store water from rainfalls of varies intensities, in soil in an usable manner i.e. water
should be stored at low matric potentials as much as possible. When water is stored in soil
matrix it will be in a negative pressure relative to atmosphere. Surface water and water in
water table has zero matric pressure.
In water balancing calculations for an ecosystem (or for the whole country) one cannot say
that the total outflow from a ecosystem (or from the whole country through rivers etc)
through underground seepage or upland rivers could be used, or in other words that one
can stop these flows and use that water for other purposes, because this will disturb and
unbalance the ecosystem. Negative outcomes of the projects of damming perennial rivers
throughout the world are well documented23. Principles of indigenous water management
in Sri Lanka do not allow us to treat water after use for irrigation as total waste. Water
balance calculations should be done based on the ecosystems perspective i.e. by
considering the whole ecosystem, its activities functions etc. related to all of its flora and
fauna. Also it should be mentioned here that water used by any particular crop or
cultivation also should be determined according to this perspective. In this case we may
have to redefine the efficiency terms related to these aspects. Proper ecosystem based
studies have to be carried out.
(b). As mentioned in section 7, water management projects related to paddy cultivation should
be based on the ecosystem perspective instead of on the crop water requirement of the
paddy plant.
(c). Cultural practices such as Bethma method should be introduced wherever possible. Also
instead of considering only on paddy, ecosystem based chena cultivation and home garden
cultivation should also be promoted.
(d). The trend is that the decisions such as the amounts of water that should be allocated for
irrigation and hydropower generation are determined by the market price of paddy and
electricity. This however distorts the sustainability of the ecosystem. Therefore a proper
22 Dr James Handawela, Deputy Director of Irrigation 23 McCully, 1996
24
national based valuing system should be introduced for paddy, electricity etc in the
ecosystem perspective.
(e). Today most of the irrigation projects, which have not shown expected results like for
example Lunugamvehera and Udawalawe are based on large reservoirs identified from a
map described as the Water Resources Development Plan of Ceylon,1959 (Mendis, 2002).
This Plan does not identify (give proper value) to the ancient structures Wewa, Vetiya etc,
which facilitated water storage, purification and conveyance through soil. This map was
derived from the 1 mile to an inch topographical survey sheets, and 100-foot contours are
shown. The dams of these projects have been located too close to the sea thus reducing the
re-use of water. The proposed Moragahakanda project is also identified from this map.
(f). Projects selected from this map and based on a modern hydraulic-civil engineering
perspective are not concerned about our ecosystem based perspective which has been time
tested for thousands of years. There have been many adverse consequences.
(g). For example, in Lunugamvehera project about 12 small Wewas, which were within the
storage area, and 30 Wewas in the command area have been demolished. According to the
Village Headman of Lunugamvehera Mr Punchi Appuhami, prior to the project, before the
construction of the massive dam, all these interconnected wewas had functioned in a
typical ecosystem with the reusing of water. Almost all the necessary food items such as
jak, coconuts etc. were produced in this system. Now water in the Lunugamvehera tank is
not sufficient to feed the estimated command area and farmers are moving in to the
direction of cash crops, which require less water, such as banana. Therefore now the
ecosystem has degraded physically and culturally. In this context, it is strongly
recommended to conduct a scientific study in the ecosystem perspective to determine the
actual water usability (how much of water gained from rain is used to develop the
ecosystem in a sustainable manner), in Lunugamvehera and Udawalawe areas, before and
after the construction of the dams. The results of this kind of study will provide proper
guidelines for future planning of such costly projects.
(h). In addressing water problems at present most importantly we have to change our attitudes
about water and related aspects. Here we would like to quote from an article appearing in
Scientific American (Special Report 2005) “Making every drop count” by Peter H. Gleick.
“Part of the difficulty, however, also lies in the prevalence of old ideas among water
planners. Addressing the world’s basic water problems requires fundamental changes
in how we think about water, and such changes are coming slowly. Rather than trying
endlessly to find enough water to meet hazy projection in future desires, it is time to
25
find a way to meet our present and future need with the water that is already available,
while preserving the ecological cycles that are so integral to human well being”.
This attitude towards water and related aspect is very much closer to the above said
attitudes and concepts that prevail in the Sri Lanka culture.
(i). Ecosystems are not owned by anybody, humans are also an important part of the
ecosystem and they fulfilled their requirements within the development model, not going
against the sustainability of the system. This is a cyclic relationship. But in the modern
situation development is isolated from the ecosystem, and development proceeds apart
from the ecosystem. Only when the ecosystem inhibits the development the concept of
“sustainability of the ecosystem” comes to attention.
(j). Water is an integral part of the ecosystem therefore clearly it is also not owned by
anybody. Everybody could use it to fulfil their requirements within the sustainable limits
of the system. Therefore water cannot be priced and sold in a so-called “free” market.
Instead the State could get a tax from water users according to the amount of their water
usages. This tax is actually a contribution to the development of the ecosystem. If a person
uses water beyond his requirement he has to contribute in a proportional manner i.e. if
somebody uses water beyond his requirement he does it due to his ability to contribute
more to the system in a less selfish manner.
(k). Water is a scarce resource. But unlike a commodity such as fossil-fuel water is in a cycle,
and being chemically stable, water could be reused many times within the water cycle
without breaking the cycle. In ancient water management this reusing was mainly
facilitated by soil, vegetation and atmosphere. This was almost a natural “reuse”. The
concept of the King Parakramabahu the Great was to reuse the water received from rain as
many times as possible before it drained to the sea. Today the construction of massive
dams in order to block perennial rivers will certainly interrupt the water cycle and hence
the ecosystem will have negative results. Unlike in almost all the modern development
projects, which gives rise to negative environmental effects, the ancient wewa has had
positive environmental effects!
26
10. References
1. Amerasinghe A R B, Judgement in the Supreme Court Application No. 884 / 99 (FR) published in Mendis, D L O, Pugwash, Globalization and Eppawala – Pugwash Betrayed? Or Eppawala Betrayed? pages 90 – 150, (2000). Vishwa Lekha.
2. Arumugam S. Water Resources of Ceylon (1969) Water Resources Board
3. Sanmugam Arumugam Commemoration volume, Water for People and Nature (2003).
Vishwa Lekha.
4. Avusadahami, Udula Bandara, 2000. Weva.
5. Brohier R L, Ancient Irrigation Works in Ceylon 3 vols. (1934) Government press.
6. Brohier R L, “Inter-relation of Groups of Reservoirs and Channels in Ceylon”. Journal of the Royal Asiatic Society, Ceylon Branch. Vol. 34. No. 90 (1937).
7. Brohier R L, The history irrigation and agricultural colonization in Ceylon, The
Tamankaduwa District and the Elahera – Minneriya Canal. (1941), reprinted by Academy of Sri Lankan Culture 1998
8. Dharmasena P. B, “Towards efficient utilization of surface and ground water resources
in food production under small tank system”, Proceedings of the Workshop on Food Security and Small tank System in Sri Lanka, 9. Sep.2000. NSF Colombo.
9. Hayley F A, The Laws and Customs of the Sinhalese - Kandyan Law, 1923. Re-printed
Navrang, New Delhi, 1993
10. Geiger, Wilheim. Mahavamsa (Translated from the German). Government press. 1958
11. Gleick Peter H.. Scientific American (Special Report 2005) “Making every drop count”
12. Lansing, Steven. Priests and Programmers – Technologies of Power in the Engineered Landscape of Bali. Princeton. 1991
13. Leach E R, Pul Eliya. Sooriya publication Colombo, 2003.
14. Patrick McCully, Silenced Rivers The Ecology and Politics of Large Dams, Zed books London and New Jersey, 1996.
15. Medduma Bandara. “Small tank cascade systems”
16. Mendis D L O, “Evolution and Development of Irrigation Ecosystems and Social
Formations in Ancient Sri Lanka”. Transactions of the Institution of Engineers, Sri Lanka, 1986
17. Water and Soil Conservation Ecosystems from Ancient Dry Zone Forest Garden to
Modern Jaffna Market Garden. Vishwa Lekha, 2001
18. Mendis D L O, Water Heritage of Sri Lanka, Vishwa Lekha (2002)
19. Panabokke C. R., “The Nature and properties of small tank system of the dry zone and their sustainable production thresholds”, Proceedings of the Workshop on Food security and Small tank System in Sri Lanka, 9. Sep.2000. NSF Colombo
27
20. Parker H. Ancient Ceylon. Lusacs, London, 1908
21. Pfffafenberger B, “The Harsh Facts of Hydraulics: Technology and Society in Sri Lanka’s Traditonal Colonization Schemes”. Technology and Culture, July 1990
22. Weeramantry C G, Environmental Aspects of Sri Lanka’s Ancient Irrigation System.
Separate Opinion, in the Gabcikovo Nagymaros case, International Court of Justice, The Hague. Vishwa Lekha, 2000
23. Weeramantry C G, “The Significance of Sri Lanka’s Ancient Irrigation Technology to
Modern Environmental Law”. Foreword, Arumugam Commemoration volume, 2003
24. Wijewardena, Ray, “Water and Soil Conservation Ecosystems of Sri Lanka”. Preface, Arumugam Commemoration volume, 2003
Resource persons
Mahamankadavala Piyarathana Thera, Eppawala
Dr. James Handawela,
Dr. P. B. Dharmasena, Deputy Director, Field Crops Research Institute, Maha Illukmallama
Dr. Ray Wijewardena, Chancellor University of Moratuwa
Mr. K. M. P. S. Bandara, Department of Irrigation
Mr. Ranjith Rathnayake, Villager at Puleliya
Mr. Prabath Vitharana, Dept. of Agrarian Services
Mr. Punchi Appuhami Village headmen, Lunugamvehera.
28
Appendix I
In ancient systems
1) Local spatial and temporal variation of rainfall and rainfall intensity and natural flows
2) Local spatial ground conditions – matric potential characteristics of soil, infiltration, soil depth
etc. were very much considered
• Water was conserved with highest possible matric potential – when water is stored in soil
its pressure is below the atmospheric pressure. This is due to the attractive forces from
water molicules from the soil matrix.
• Reduce water out flow – this was achieved by considering the topography of the local
bedrock also.
• Water in ecosystem = Blood in body
Unlike a fossil fuel water is in a cycle
• In traditional system, the cyclicity has been improved. This was the main idea behind the
famous statement of the King Parakkrama Bahu the Great: “Let not a drop of water that
falls on this land be allowed to flow into the sea without being made useful to man”.
Rain
sea
Rain
sea
Water
Reuse of water
Pota Vetiya
Kulu vewa
Vewa
29
Appendix II
River Maker at Rajastan India
Rajendra Singh makes rivers flow in the desert as Rajastan using a traditional Indian water
conservation method known as “Johad”. It looks like a semi circular pond, collecting the run off
from tiny streams and rivulets in a much wider area, and allowing it to percolate down and
recharge the ground water below (New Scientist September 2002).
“Traditional knowledge is dismissed
as unscientific. But what’s really
unscientific is not trying to
understand local ecology, climate soil
and culture”