< p >好地下水质量是至关重要的作物yield, soil productivity and environmental protection. Suitability of groundwater for irrigation purposes is determined by its geochemistry. Groundwater geochemistry explains links between chemical composition of groundwater and subsurface geological and non-geological pollutants. Subsurface rock formations control the composition of soil and hence that of water and vegetation. The ground water samples were analyzed for physico-chemical parameters like Electrical Conductivity (EC), Hydrogen ion concentration (pH), Bicarbonate (HCO₃^-), Calcium (Ca²⁺), Magnesium (Mg²⁺), Sodium (Na⁺), Potassium (K⁺), Sulphate (SO₄^2-), Nitrate (NO₃^-), and Chloride (Cl^-). Inverse distance weighted method of the Geographical Information Systems is used to prepare the distribution map of physio-chemical parameters of groundwater while overlay method is used to assess spatial, temporal changes and prepare groundwater quality zones of Walayar watershed in Parambikulam-Aliyar-Palar basin situated in Coimbatore district, Tamil Nadu, India. The results of study show that the quality of groundwater varies both spatially and temporally in Walayar watershed. The groundwater samples in some of the wells showed deviation from water quality standards indicating groundwater contamination. Hence, proper care must be taken to avoid any contamination of groundwater and its quality be monitored periodically.