Groundwater is one of the most important natural resources. Groundwater has become a necessary resource over the past decades due to the increase in its usage for drinking, water supply, irrigation and industrial uses etc. Groundwater resources are now facing threats due to anthroprogenic activities. Mapping of spatial variability of groundwater quality is of vital importance and it is particularly significant where groundwater is the primary source of potable water. The present study has been undertaken to analyze the spatial variability of groundwater quality for Chinnar sub basin, Perambalur and Ariyalur District, Tamilnadu state. The study area was selected based on the Hydro geological properties. A Study on Physico-Chemical parameters of water quality in the salinity affected areas of Nagapattinam District is taken up to evaluate its suitability for drinking and irrigation purposes. Ground water samples are to be collected from the study area from Veppanthattai Taluk to Sannacinallur in Ariyalur district. The water samples collected at 65 villages and analyzed for pH, Sodium, Total Hardness, TDS, Chloride, magnesium, Calcium, Sulphates, Bicarbonates, potassium, Dissolved Oxygen. Geographic Information System (GIS) is used for spatial and temporal mapping of water quality in the study area. Geographical Information System (GIS) is used for the spatial analysis and it is a powerful tool for the representation and analysis of spatial information related to water resources.