Groundwater samples from 47 locations have been collected from various location of the Sweta Nadi, Vellar River, Tamil Nadu, India and these samples were used to assess the groundwater quality for drinking and irrigation purposes. The study area of about 602.07km2 in a part of the Vellar River basin. The physical and chemical parameters of groundwater such as pH, electrical conductivity (EC), total dissolved solids (TDS), total hardness(TH), Na+, Ca2+, Mg2+, Cl-, HCO3-, CO32-, SO42-, NO3-, F- and Fe2+were determined. The values were analyzed and compared with World Health Organization (WHO 1996) water quality standards. Suitable groundwater quality zones for drinking and irrigational purposes were identified through spatial distribution maps using GIS. Kelley’s ratio, sodium absorption ratio (SAR), Magnesium hazards, residual sodium carbonate (RSC) and permeability index (PI) were used to assess the suitability of the groundwater for irrigational purposes. The graphical interpretation of irrigational water quality was made through Wilcox diagram, Doneen diagram, USSL diagrams and Gibbs plots.
