The main contributors of high nitrate concentrations in the groundwater of the Vamsadhara River basin are the point sources associated with livestock barns while the seasonal variations in nitrate (NO3) concentrations are attributed to the prevailing hydrogeological conditions. The observed increase in nitrate under rising water level conditions, contradicting an expected decrease due to dilution by rainwater, is believed to be caused by the contribution of NO3from the clayey soil. The processes of sorption, retention and slow denitrification in clay are probably responsible for the contribution of nitrate to the groundwater in the post-monsoon season. The positive linear relationship between chloride and nitrate is in agreement with the similarities in behaviour of these ions in the clayey formations.