A review on nutrient pollution of coastal aquifers of Sri Lanka

Abstract

Nutrients such as nitrates and phosphates in the groundwater are a serious concern in certain parts of Sri Lanka where many rural communities depend on groundwater for their daily water supplies. In addition excess nutrients in water have lead to water quality problems such as algal blooms, eutrophication in a number of surface water bodies. Sri Lankan coast line extending over a length of nearly 1585km is one of the highly sensitive and rapidly developing areas of the country. The coastal aquifers can be subdivided into four groups according to aquifer media by which the coastal areas are characterized. Those aquifers play an important role in supplying water both for domestic and agricultural activities in the areas concern. Sri Lankan coastal groundwater resources at most places appears to be contaminated by nutrient pollutants. Elevated levels of pollutants have been often recoded in shallow karstic limestone aquifers of northern and sandy aquifers of northwestern and northeastern coastal zones. It is revealed that the behavior of nutrients in groundwater is mainly governed by intrinsic properties of aquifer media and the distribution of nutrients shows a clear correlation with anthropogenic activities and land use pattern of the coastal areas. The most commonly recorded nutrient in coastal groundwater is nitrate. With regard to phosphate concentrations however, Sri Lankan coastal groundwater is presently safe though shows increasing trend of future vulnerability. It is inferred that coastal sandy aquifers in Sri Lanka are at risk and need an immediate protection effort with comprehensive investigations, introducing preventive measures and establishing a long term monitoring setup.