Assessment of the chemical facies of groundwater using factor analysis in the Chunnagam aquifer, Jaffna Peninsula

Abstract

The Jaffna Peninsula has four main types of aquifer systems, namely,Chunnakam (in the Valikamam area), Thenmaradchi, Vadamaradchi, and Kayts. The water resources of the Valikamam region depend totally on rainfall recharge to the Miocene limestone aquifer. Valikamam is an intensified agricultural and high population density area in the Jaffna Peninsula. Groundwater is an extremely valuable resource and the pollution of groundwater resources is a matter of serious concern in the Jaffna Peninsula. Therefore, this study examines the hydro-chemical facies of groundwater in the Chunnakam aquifer using factor analysis. Forty four wells were selected to represent the entire Chunnakam aquifer during the months of January, March, April, July and October 2011 to denote various rainfall regimes within a year. Samples were analyzed for Electrical Conductivity (EC), pH, chloride, nitrate as nitrogen, calcium, magnesium, carbonate, bicarbonate, sulfate, sodium and potassium concentration based on Sri Lankan Standard (SLS) procedure. Groundwater was classified based on the Chadha diagram and factor analysis was performed using software XLSTAT 2012. Interpretation of the hydro-chemical analysis reveals that the groundwater of Chunnakam aquifer is alkaline in nature. All water quality parameters except EC, NO3- as N, and SO42- are within the Sri Lankan Standard for drinking purposes. Two major hydro-chemical facies Ca2+-Mg2+-Cl- and Na+ -Cl- -SO4 2- were identified using the Chadha diagram and permanent hardness and salinity problems were deemed probable. Salinization, water soil/rock interaction, and anthropogenic activities are identified in the factor analysis. Salinity development and high nitrate as nitrogen content in drinking water are problems identified in the Chunnakam aquifer.