A detailed hydrogeochemical study was carried out in Lekkur sub basin which is part of Vellar basin. Groundwater is the major source of water supply for agricultural and domestic uses. The agricultural and urbanization activities have a lot of impact on the groundwater quality of the study area. In order to understand the water quality variations within the sub basin, groundwater samples were collected from dug wells and hand pumps during post monsoon season. These water samples were analysed for major cations and anions. The water analysis data was processed using a computer programme HYCH. In this programme, numerical steps are adopted for the hydrochemical facies classification using the criteria of Handa, Piper, Stuyfzand and USSL schemes. According to Stuyfzand classification, 50 % of waters are oligohaline to fresh type. Half of the water samples are coming under C2S1 and C3S1 types. When plotted in the USSL diagram for classification of irrigational waters, it indicates that the water is of moderate salinity and low sodium hazard and hence can be used for agriculture practices. Rest of the groundwater samples shows serious problems for domestic and agricultural uses during post monsoon season.
