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Post subject: Ecosystem based indigenous water management
Sat Jun 21, 2008 6:07 am
|Ecosystem based indigenous water management
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 renowned authorities in this field this was a sustainable water - soil - flora fauna - human ecosystem, which was mainly based on small tanks (Wewa) in Rajarata and Ruhuna, and basically on anicuts in Mayarata (i.e. mainly the wet zone). The history of this ecosystem leads back to the 4th century B.C. or before. Basawakkulama sometimes known as "Abhayawewa" was identified as the most ancient Wewa, which was done 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 Rajarata
© 2006 Practical Action. All rights reserved.
Posted in LL June 2008
1. Background of the report
The main objective of this report 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 out lined.
Indigenous water-ecosystem management cannot be simplified to its physical structures and practices. Presently, the physical structures and practices are taken isolated from the cultural aspects and then the governing economic development model has little meaning. Therefore the intention of this report 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 matter to solve some of the problems related to water (ecosystem) in today's context.
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 renowned authorities (Eng. D L O Mendis, Dr. Ray Wejewardene) in this field this was a sustainable water - soil - flora fauna - human ecosystem, which was mainly based on small tanks (Wewa) in Rajarata and Ruhuna, and basically on anicuts in Mayarata (i.e. mainly the wet zone). The history of this ecosystem leads back to the 4th century B.C. or before. Basawakkulama sometimes known as "Abhayawewa" was identified as the most ancient Wewa, which was done 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 Rajarata .
The backbone of this ecosystem was its ability to store the rainfall water 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 to roots in this region), the ancient "hydraulic system" was focused on the water requirement of the entire ecosystem. To fulfil this requirement, various types of structures such as major tanks, small tanks, Vetiyas, Amuna, Vila (lake), Wala (Pond) etc. (Figure 1) and inter connecting canals were constructed very much closer to the 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 an example Elahera-Parakkramasagaraya. In some other areas this was happened totally the other way round, i.e. spilling out water from small-tanks was stored in major tanks. For examples Kuluwewas ( Small surface storage consisting of earth bunds used as a silt trap, flow controller for flood mitigation raising the water table in vicinity.), which are incorporated in most of the ancient systems. In almost all these cases small tanks were constructed in cascade system, which facilitated efficient reuse of water. In this manner these structures were used to store water in the ecosystem (i.e. in the soil) in drought periods and was used in flood mitigation in rainy periods. It should be mentioned here that irrigation was only a part of this hydraulic system.
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 of these ecosystems is not only due to there physical structures mentioned earlier. The culture prevailed in these settlements also provided necessary conditions for this sustainability. This culture can assume to be driven not by the self-interest motivated by greed, but by the other motivation like sharing resources equally (even among animals, birds etc.) and the equity of ownership. The statement of Arahat Mahinda states that the king is only the guardian of nature and not the owner. Keeping a Kurulupaluwa (portion of paddy field reserved for birds) would have been a direct outcome of this concept. This culture with that concept proves that, we are just guardians of the nature of the physical structures like wewa to served this ecosystem to function for thousands of years. Actually, in this culture-ecosystem had the in built development model which is suitable for us i.e. our environment & culture. Now we are almost totally apart from this tradition. Today we do not have an idea about our development model and therefore we cannot rehabilitate these ecosystems in a sustainable manner. Anyhow it should be mentioned here that though 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 of ancient cultural context water management was not taken as an isolated issue. Hear, the main objective of water management is to optimize the conditions of the proper function of the ecosystem. Water was mainly stored, in the soil and conveyed through the soil and the soil facilitated mainly the water purification process. Water was taken from the soil (from water table) then the used water is again put to the soil, which purify the water and feed the water table for reuse. Water was conserved in the soil (i.e. maintaining the water table). To facilitate this conservation physical structures like cascade wewa system; (in Rajarata) Vetiya (in southern area) Amuna were built according to the geophysical nature of the region. In this manner water receive from the two monsoons was reused several times before it ultimately drained to the sea. Even the inter monsoon rains (Akvehi) would have facilitated this reuse process (i.e. cyclicity). The water evaporated from the wewas help to create convection rains (Akvehi)( 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) i.e. 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 life.
4. Concepts, attitudes related to the sustainable-development model (for ecosystems)
Buddhism was significantly influenced the Sri Lankan life style (e.g. attitudes, concepts). Some of such prominent Buddhist concepts are listed below.
[list=]Greed (Thanha) is the cause for sorrow Dukha. Therefore it should be decreased( Buddhist Sutrapitake - Load Buddha) .
Happiness is the most impotent wealth. ("Santhutti paramang Dhanang") ( Buddhist Sutrapitake - Load Buddha)
Equity of ownership
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 much disturbing much to the other partners. Statement of Arahant Mahinda.
Less selfish, holistic community based approach to optimise the ecosystem.
Holistic approach towards nature . [/list]
5. Structural features and practices of this ecosystem
5.1 Rain water trapping structures
In the ancient water management, amount of rainfall (nowadays measured in "mm") and the intensity of rainfall (nowadays measured in "mm/day") were deliberated. Small structures like Vetiya captures the water from very low intensity rainfall. Small tanks capture the water from much higher rainfalls and major tanks capture water from even higher rainfalls .
There are about 12,000 small tanks and anicuts found in Sri Lanka and these tanks and anicuts irrigate an extent of about 185,000ha. This is 35% of total irrigable area in the country. Small irrigation schemes produce 191,000mt annually accounting for 20% of the national irrigated rice production (Agricultural implementation programme 1994 - 95). 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 tanks spill out. Naturally grown large trees such as Kumbuk, Nabada, Maila, Damba etc. and climbers such as Kaila, Elipaththa, Kakukeliya, kalawel, bokalawel etc. are subsisted 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 constructed soil ridge in the upstream of the tank at either side of the tank bund to prevent entering the eroded soil from upper land slopes.
Godawala - A manmade water hole to trap sediment and it provides water to wild animals. This might be a strategy used to evade man-animal conflict.
Kuluwewa - A small tank constructed above the relatively large reservoirs only to trap sediment and not for irrigation purposes. 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 the sanitary purposes 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. This land phase prevents entering salts and ferric ions 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 etc. . Specifically they harvest row materials from this vegetation for cottage industries.
Figure 3: Essential components of a village tank 
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 
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 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 of the tanks are situated within a single meso-catchment basin. These meso-catchment basins could be varied in extent from 6 to 10 sq.miles, with a model value of 8 sq. miles in the North Central Province region.
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 is 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 are shown in the same diagram. These small tanks from 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 reservoirs .
Figure 5: Schematic representation of small tank cascade 
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 lives, are sheared among the people in the ecosystem. Ecosystem does not belong or owns to any body. In other words, ecosystem is virtually not divided among people instead outcomes are sheared. 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 to gather and, an area, which could be cultivated with the limited water is cultivated and the harvest (paddy) is divided among them.
5.4 Thattumaru method
This is adopted by villages, when the fragmentation of lands makes it difficult to cultivate in small unit. When a villager has a small unit, he opts to forego the cultivation of his unit giving the opportunity another to cultivate a larger unit including his. This makes operational unit more viable. Each farmer gets his turn but not every season.
5.5 Water distribution
A holistic approach - This was done according to community or group interest.
Biskotuwa is a device used by ancient engineers to control the outflow of water from wewa with considerable heights (10-15m). As shown in figure 6, the Bisokotuwa consists of a rectangular tank connected to the sluice; in almost all the cases the longer side of the rectangle is kept parallel to the bund. Though any evidence regarding the gates of the Bisokotuwa has not been found up to now, speculation about gates, which would have been made out wood and controlled, by a system of levers, shown in figure 2, are mostly accepted in the present among scholars. With these speculated gates the function of the Bisokotuwa could be explained as follows.
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 have not 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 out side canal driven by the head of the Bisokotuwa, hence without subjecting the sluice across bund to high pressure as well as velocities created directly from the head of the wewa. When stopping the water release from the wewa, gate A is closed then water inside in the Bisokotuwa will flow through sluice XY (Figure 6) 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 are already mentioned are not needed.
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-it is an effective expansion tank. This may probably be reason for laying the Bisokotuwa in such as way that its longer side is parallel to the bund i.e perpendicular to the sluice- the direction of water flow. In the Bisokotuwa the flow (and pressure) of water outgoing from wewas with high heads are controlled by dissipating energy in the water by letting it expand in the Bisokotuwa or rather by letting the water coming to the Bisokotuwa to collide with water inside the Bisokotuwa and thereby releasing its energy by a marvelous 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 fulfill this requirement. In some wewas, for example Urusita wewa at Sooriyawewa, water enters the Bisokotuwa by one conduit (sluice) at the bottom center and goes out by two conduits beginning 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 be not harmful to the bund as well as to the outgoing canal.
The Bisokotuwa is also used to divert water flows. One such example is seen at an outlet in Parakrama Samudra. 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 effects such as erosion of conduits take place.
Figure 6: Schematic diagram of Bisokotuwa
This provides a more even, simple distribution method when compared with modern methods. Once a certain amount of water released from the wewa each and every plot will approximately get an equal amount of water. No body is needed to regulate water from plot to plot.
Figure 9 -Water dividing devices (Karahana) used in cannels in Puleliya 
Figure 10: Water distribution methods 
A community based maintenance methodology for the ecosystem. In this method, about 40 days of each year villages worked for the benefit of the whole community (ecosystem).
5.7 Trans basin canals developed within the ecosystems
Holistic approach, insitu time tested irregation and water supply projects developed gradually. eg : Jaya Ganga:-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 the overflow from the tank higher up on each chain".
Parakrama Sagaraya:- 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".
5.8 Construction of anicuts
Construction of anicuts across water flows such as perennial rivers to direct water for canals were also a major part in the ancient water management system. In this case, dams were built obliquely across (or sometimes halfway) the flow ("Redibendilla"). This would have resulted in less silt acumination above the anicut (proper studies has to carried out in the aspects). In some cases there construction were temporary. Any way us all these cases the ancient engineers were very much concern about the ecosystem and the behaviour of the silt. The constructions were done to reduce the accumulation of silt and providing methods to washout the accumulated silt. Also in these constructions the natural flows were not interrupted totally. Proper studies have to be carried out in order to get the ancient knowledge of the construction of anicuts etc without disturbing the ecosystem.
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 ecosystem
Ecosystem perspective ( A perspective, which is based on the sustainable development of human and environment with in the context of Sri Lankan culture.) - water received as rain is stored in the ecosystem in a usable manner then used and drainage is again fed to the system and reuses several times.
Small water cycles through soil: - Water cycle is connected with soil in local vicinity.
Water purification is mainly done by the soil
Irrigated whole land together water conserved, conveyed through the soil or unlined canals
Evaporation (specially from wewa) is facilitated local water cycles as they give rise to convectional rain (Akvehi)
People live along the cascade, this facilitated reuse of water
According to above reasons, water has been reused.
6.2 Modern system
Storage tank perspective - water gained from rain is stored in tanks, then used and drainage. Water cycle is large connected with sea or other reservoirs, mainly through pipeline, concrete cannels (i.e. water supply and derange).
Water cycle is less connected with the soil in local vicinity
Less water purification by the soil (pollution is also high)
Less water reuse
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 this will give rise for water shortages, in the region. Also for towns water is pumped from rivers and other sources, no reuse as in a wewa in village. Population is clustered in towns unlike in cascade systems.
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 very much closer to the nature and with very much less pollution  ( Mahamankadavala Piyarathana Thera at 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 waterways 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 mentioned here that actually 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 as small wewas. Rainfall water, which could have easily drained 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. Paddy a plant, which could withstand flood condition were grown in these "wewas". Therefore one cannot directly say that water in paddy fields are, a requirement of paddy, and paddy is a crop, which "waste" water. Therefore proper studies has to be carried out on this matters based on ecosystem perspective.
It is worthwhile to coat the following phase from "rice paddy ecosystem" in Bali by Steve Lansing because it would be much 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."
8. Evolution and Development of Irrigation Eco-Systems in Ancient Sri Lanka 
Water management cannot be identified as an isolated issue. It is highly related to the economic development model- related activities, physical structures-practices and concepts-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 based 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 soil separately for each geophysical situations. 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 atmosphere) is ignored. Evaporation from tanks (wewaa) and seepage are taken as losses!
Also instead of net rainfall, rainfall intensity (mm/day) has to be taken in to account . 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 a ecosystem (or for the whole country) one cannot say that the total out flow from a ecosystem (or from the whole country through rivers etc) through underground seepage or upland rivers could be used totally, or in other words that one can stop these flows and use that water for other purposes. Because this might disturb and unbalance the ecosystem. Negative out comes of the projects of damming perennial rivers throughout the world are well documented . Principles of indigenous water management do not allow us to treat as total waste. Water balance calculations are done based on ecosystem perspective i.e. by considering the whole ecosystem, its activities functions etc. related to all of its flora & fauna. Also it should be mentioned here that water used by a 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 has to be carried out.
(b). As mentioned in section 7, in water management projects related to the paddy cultivation one should based on ecosystem perspective instead 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 be promoted.
(d). The trend is that the decisions such as how 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 national based valuing system should be introduced for paddy, electricity etc in the ecosystem perspective.
(e). Today most of the irrigation projects, which has not shown proper results (E.g. Lunugamvehera, Udawalawe) has been carried out on the basis of a map described as the water recourses development map of Ceylon-1959, which does not identify (give proper value) the ancient structures Wewa, Vetiya etc, which facilitated water storing purification conveying through soil. This map is 1 mile to an inch and 100-foot contours are shown. Also according to Eng. D L O Mendis, the dams of these projects have been situated too much closer to the sea. This will reduced the reuse of water. The proposed Moragahakanda project is also based on this map the projects carried out based on this map and on modern hydraulic-civil engineering perspective do not concern about our ecosystem base perspective which has been time tested for thousands of years.
(f). In Lunugamvehera project about 12 small Wewas, which were with in the storage area, and 30 Wewas in the command area has been demolish. Prior to the project i.e. before the construction of the massive dam all these interconnected wewas had been functioned in a typical ecosystem with the reusing of water . Almost all the necessary food items such as jack coconuts 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 proposed to conduct a proper study in the ecosystem perspective to determine the actual water usability (how much of water i.e. gained by rain is used to develop the ecosystem in a sustainable manner), in Lunugamvehera and Udawalawe area prior and after the construction of the dam, the results of this kind of study will provide proper guidelines for future such projects.
(g). In addressing water problems at present most importantly we have to change our minds, attitudes about water and related aspects. Here we would like to quote a part from an article appeared 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 find a way to meet our present and future need with the water i.e. already available, while preserving the ecological cycle that are so integral to human well been. This attitude towards water and related aspect is very much closer to the above said attitudes and concepts prevail in Sri Lanka in its culture.
(h). Ecosystems are not owned by anybody, humans are also a part of the ecosystem and they fulfil their requirements arise with in the development model, which is intern, not going against the sustainability of the system. This is cyclic relationship. Unlike in modern situation where development is isolated from ecosystem and development is proceeded apart from the ecosystem and only when ecosystem inhibits the development the concept of "sustainability of the ecosystem" comes to the context.
(i). Water is an integral part of the ecosystem therefore clearly it is also not owned by anybody. Every body could use it to fulfil their requirements with in the sustainable limits of the system. Therefore water cannot be prized and soled in a "free" market. Instead the state could get a tax from water uses according to their amount of 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 some body uses water beyond his requirement he does it due to his ability to contribute more to the system in a less selfish manner.
(j). Water is a scarce resource. But unlike a commodity such as fossil-full water is in a cycle and being chemically much stable substance water could be reuse many times within the water cycle without breaking the cycle. In ancient water management this reusing was mainly facilitated by soil and atmosphere. This was almost a natural "reuse". Today the construction of massive dams in odder to block perennial rivers will certainly interrupt the water cycle and hence the ecosystem will have negative results. The concept of the king Parakramabahu the great was to reuse the water received from rain many times as possible before it drain to the sea.
1. Brohier R L, The history irrigation and agricultural colonization in Ceylon, The Tamankaduwa District and the Elahera - Minneriya Canal. Academy of Sri Lankan Culture 1998
2. 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.
3. Leech E R, "Pull Eliya" Sooriya publication Colombo, 2003.
4. Mendis D L O, Water Heritage of Sri Lanka, Sri Lanka pugwash Group - Colombo 2002
5. Panabokke C. R., The Nature & 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
6. Patrick Mccully, Silenced Rivers the ecology and politics of large dams, set books London and New jersey, 1996.
7. Mahamankadavala Piyarathana Thera, Eppawala
8. Dr. Hadawela,
9. Dr. P. B. Dharmasena, Deputy Director, Field Crops Research Institute, Maha Illukmallama
10. Dr. Ray Wijewardena, Chancellor University of Moratuwa
11. Mr. K. M. P. S. Bandara, Department of Irrigation
12. Mr. Ranjith Rathnayake, Villager at Palleliya
13. Mr. Prabath Vitharana, Dept. of Agrarian Services
14. Mr. Punch Appuhami Villag
© 2006 Practical Action. All rights reserved.
Irrigation and water management in Ancient Sri Lanka
Vewa - The man-made reservoirs
Kala Wewa (Reservoir) - 470 AD
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