Summarising Impacts and Recommendation on Lagoon Schemes in Jaffna Peninsula
Professor. R. Sivachanthiran (Rtd) – Director, Chithanaikoodam, Centre of Research & Development Jaffna
Fresh water of lagoon schemes in Ariyalai and Thondamanaru were completed in 1955 and 1953. The leaching action of the lagoon is a slow process on account of the limited catchment (rapid urbanization adjoining) area drain into the internal lagoons.
Further, construction of the Elephant pass lagoon scheme commenced in 1962. When completed it received two major setbacks. At the western end sea water was leaking in considerable quantity through the P.W.D road into the lagoon. Preventive measures that were taken subsequently became successful. The second set back was the damage to the eastern closure bund that was probably to the settlement of the sub soil below the bund. The bund had settled, had been overtopped and was breached during one of the floods. In the economic study, only the primary benefits from agricultural production had been evaluated. The reaching of the underground storage, to benefit the brackish wells and to increase the storage potential of the ground water to meet the increased demand for irrigation and domestic use had not been considered.
Conversion of lagoon from salt water to fresh water reservoirs is impractical for two reasons. Firstly, evaporation and percolation loss consume nearly all the average annual rainfall. An estimated 98% of the inflow to the Uppu Aru lagoon and 99% of inflow to the combined Vadamarachchi- Elephant pass lagoon is lost to evaporation and percolation. In most years, the lagoon dries up during the dry season. Secondly, the salinity levels during the dry season commonly range from one – half to five times that of sea water.
By closing down the free flow of sea water from Keratheivu in the west to Chundikulam sand bar mouth in the east by a bund at Elephant pass. The impact of sea water on the Elephant pass road cum railway embankment causes the water to turn in the opposite direction with the same force y and this return flow meets the sea waves from the west and at this point the resultant water get directed in to the low lying land along the southern side main land through the streams of the main river that is known as Kudamuriddi Aru which flows from the basin of Maruthankulam, Akkaraiyankulam tanks and smaller culvert outlets on the Paranthan –Poonakary road. This water has got mixed up with the rain water that collected in depressions known as villus which had caused the trees of the scrub jungle trees such as Paalai, Veerai etc. to die. The dead tree trunks are seen in the open land along the road, thereby causing the low lying land in these belts to become saline with grassless parched earth. To prevent this intrusion of sea water, all minor culverts could be closed down and on the major culverts and at the stream crossing, semi-circular concrete walls needs to be constructed to 3.0 MSL, which is about the high tide level, to prevent sea water entry into the land side.
The salt water exclusion scheme at Elephant pass- Chundikulam was to form a Lake and to discharge this water into Vadamarachchi lagoon through the inlet channel. However this water begins to dry up due to evaporation from May onwards and by September this lake bed is completely devoid of water and appears as an extensive parched open stretch. Similar situation prevail in the fresh water lake areas enclosed by Thondamanaru barrage and Chemmanni – Navatkuli Barrage. Since the construction of these barrages some notable changes have taken place to the open wells in the peninsula along the periphery of the basins of these above lagoons. The ground water table had appeared to go down and water in wells began to turn saline during the dry months from May to September although this problem was not observed before these Barrage came into being. Effect of Barrage has to be studied and remedial measures needs to be taken.
Due to the loss of lagoon sea water by leaching in these proposed fresh water lakes, the lagoon sea fishermen who used to engage themselves in quick fish catching with simple implements have lost employment which had been in existence near their dwellings and the fish consuming communities are deprived of their palatable food that they have been used to and have enjoyed over the years . It may be due to the lack of fishing facilities like earlier the barrage gates at Thondamanaru and Chemmanni are being trampled slyly. Solution to this problem too has to be found.
A seminar was held recently at the Mahatma Ghandi centre in Kirulapone for the reawakening of the long – delayed “A river for Jaffna project “. The chief spokesperson at the seminar was Dr.D.L.O.Mendis, who briefly outlined the project. This was followed by a discussion that was attended by number of senior engineers.
During the discussion “the conversion of Vadamarachchi and Upparu lagoon as well as the Elephant pass lagoon into fresh water considered a massive environmental issue with resulting changes need to be properly looked at. There are hundreds of fisher families who lives alone in the borders of the three lagoons depends on the saline water where fish, prawns and crabs thrive. Jaffna is famous for its huge prawns and crabs and any changes to salinity levels will affect the growth of prawns and crabs. There had been suggestion of introducing fresh water prawn into the salinity – changing lagoons, butt has any research been carried out over the issue? Can the newly introduced prawns and crabs give the same yield to the fisher men? Anyway, no funding agency will provide funds to a project which neglects environmental issues.
Present status of water supply in Jaffna peninsula
Currently 23 rural water supply schemes are being operated by NWSDB and local authority in Jaffna peninsula and the total coverage of pipe borne water supply through stand post is 3.2% and less than 0.5% of the households in Jaffna peninsula have access to piped water, these supplies are also limited to one hour and people fetch the water in queues. There has been is no major water supply development in over three decades. Affected places are covered by NWSDB through Jaffna Killinochi water supply and sanitation project. There are a number of deficiencies in the present system. The soak away pit of septic tanks constructed in sandy and in lime stone areas are often close to domestics wells. The soils have high percolation capacity and promote flow of effluent into the ground water body and hence potentially to the house hold wells. It was observed that for the average household of 5.5% septic tanks pit de-sledging had not been carried out in over 8 years and there was
no overflow which demonstrates the high absorption capacity of the ground. The water table in the coasted areas is between 1 and 1.5m below the tank bottom at the end of the dry season, and during wet season the water table rises to ground level. This will promote the movement of the coliform and pathogen to the existing wells. When the ground water table is low, much below the tank base there may be less change of pathogens reaching the wells.
Septic tanks and soak away pits are located too close to buildings and are shallow. The minimum required clearance distance from the wells is 15 to 30 metres for coarse sand and for gravels. For septic tanks in Karstic limestone there is no easily identifiable safe distance as pollution can cover large distances through the solution channel very quickly.
“According to the results of water samples tested, the ground water of the study area is polluted due to heavy agricultural practices. Mainly in shallow aquifer ground water, some parts of Jaffna peninsula is totally polluted with nitrate. The usage of excess amount of nitrogen fertilizer, pesticide, weedicide, and shallow ground water table are the major reasons for this issue. Chunnagam, Kopay and Kondavil areas (red bed areas) are identified as the most nitrate high areas. Among other study areas, suggest that high e number of stomach cancer patients are reported in these regions. The farmers in these areas should be encouraged to use excess amount of organic composed instead of using higher amount of nitrogen fertilizers, pesticide and weedicide. The wells which are located very near to the Lagoon are totally contaminated by salts water. The over extraction of ground water has also created the salts water intrusion. The best ground water sources are identified in sand dune aquifer (Vadamarachchi east area up to Iyakkachchi). Fresh water lens and deepen sea could be the reason for that. This aquifer should be protected from pollution and over extraction”.
It is technically possible to transfer any water from one place to another place using gravity or pumping. Already new technology has been developed to pump water without any wastage of water. Also transferring water through pipeline in comparison to open channel (more evaporated seepage loss) is financially cheaper. When compared in long term pipeline is more economical and convenient, due to less water loss. Currently world is adopting transferring of water by pipeline very efficiently. Our society and technocrats think on this direction. Now all are living in a globalized world and are thinking out of the box. Freshening of lagoons cannot be done by engineers alone. A team of experts that consist of technical, social, environments, hydro-geo chemist, ecologist & etc should come together to find solutions to the problems. Without these experts knowledge, the acceptance of the project (Jaffna lagoon scheme) will not move forward and it will be questioned and criticised.
The ground water quality is getting worse in Jaffna peninsula. Presently the ground water is highly contaminated with nitrates, bacteria – coliforms and oil. The presence of heavy metals in ground water needs to be tested. Therefore the government has to ensure and provide sustainable water supply to the Jaffna peninsula.
The rivers for Jaffna shall improve the agriculture land but it will not resolve the water supply issue. Also the study of river for Jaffna should be reviewed with new concepts and should be implemented by the ministry of the irrigation land affairs to improve the productivity of the agricultural lands.
References:
Elephant pass lagoon scheme, Dr.(Eng) S.S.Sivakumar,head –Civil Engineering, senior Lecturer, department of Civil Engineering, Faculty of engineering, university of Jaffna and former deputy director of irrigation (Mulatitivu) and project director of ENREP
Water resources development Jaffna peninsula, late Eng.K.Sanmugarajah, former deputy director irrigation department.
Executive summary reports markets town water supply Jaffna project, NWSDB 1984
