Water quality of some wells in Jaffna and Kilinochchi with special reference to nitrate pollution

Abstract

Water samples from 65 wells in the Jaffna and Kilinochchi districts were analysed for pH, EC, Na, K, Ca, Mg. P and NO,-N. About 65% of the wells in the Jaffna peninsula had high salinity water; la the Islands more than 80% of the wells were very high in salinity. Most wells in Kilinochchi however, were medium in salinity. With respect to Na-hazard most wells fell into the low to medium-Na water categories. Potassium contents were low to medium in the wells of Jaffna peninsula and Kilinochchl, but very high in the Islands. Phosphorus levels were extremely low in the wells tested. Nitrate-N in majority of farm wells were much higher than the permissible level of 11.3 ppm N stipulated by WHO for drinking water. Domestic wells on the other hand had low NO, levels. It appears that high NO content in well-waters is associated with the intensive agriculture practiced in the Jaffna peninsula. Measures to minimize this increase are discussed. Owing to the substantial amounts of N and K in the well-water there are possibilities of adjusting the amounts of these nutrients added as fertilizers to crops grown in these areas.