WATER PROBLEMS IN THE JAFFNA PENINSULA

agricultural activity related to short term crops. Water for drinking and for agriculture is obtained from open wells. Even the municipal area in Jaffna is supplied with water pumped from wells located in Kondavil, about three miles from Jaffna Town. Open wells are commonly built in villages, one for each household albeit with some of them shared by three or four neighbouring households who occupants are usually related to one and another. A recent innovation is the sinking of tube-wells to obtain water supply for drinking and irrigation to agricultural lands. Quality of water and affordable water supply In the early days, well sweeps or a system of pulleys were used to extract the water from the open wells, both for consumption as drinking water and for irrigation to crops. The fresh water in the aquifers floats in lens formation or varying thickness on saline water found below and has salinity levels depending on its location and distance from the sea. For example, a study on the geomorphology of the Valukkai Aru drainage basin in the Valigamam area showed that the salinity of the ground water in a location is inversely related to its distance from the sea. (Puvaneswaran, 1987). The amount of calcium, magnesium bicarbonates and sulphates present in the water contributed to its hardness which varied from moderately hard to hard in terms of calcium carbonate equivalent. Since the rate of extraction of the underground water was relatively slow, the recharge of the wells from the underground reservoir helped to maintain an affordable water supply of satisfactory quality in terms of salinity and hardness. Ground water recharge has been viewed as a function of effective rainfall. In the Jaffna Peninsula, this occurs only during the annual monsoon rainfall during the period September to January. After losses by direct runoff (about 10-15 per cent), and losses by evaporation (about 40-48 per cent), only 30 to 32 per cent of the rainfall is left over for ground water recharge. In the last three decades, the quality of water in the region has deteriorated due to various reasons. Variability of the rainfall over the region has indirectly contributed to this as rainfall over the region has indirectly contributed to this as rainfall is the only source of recharge. A sample of rainfall records for the period 1985-1993 given in Table 1 supports the variability of seasonal rainfall. The salinity problem was perceived as a hazard as early as the 1950's and 1960's and this has been