The availability of fresh water is of concern. River basins all over the world have potential groundwater resources both quantitatively and qualitatively. But at national level, the need of the groundwater exceeds the groundwater potential and water scarcity exists. People residing near the coastal area, face a threat of saline water intrusion. It becomes essential to evaluate qualitative and quantitative assessment of existing ground water resources. Area adjacent to Gulf of Mannar, which forms a part of River Gundar basin, has been chosen for this study. The study area occupies southeastern part of Indian sub continent and surface flow is restricted only to monsoon season. Ground water sample of from 33 locations have been collected in two different seasons (pre- and post monsoon). The above samples have been analyzed and brought into a digital output using a simple program HYCH. From the digital output, thematic maps such as Total Dissolved Solids (TDS), Groundwater Classification and Salinity and Sodium Hazard have been prepared using the GIS environment. It is inferred that the quality of groundwater improves unevenly in different locations with respect to season indicating the recharge is not uniform. An appreciable amount of quality improvement has been observed along the northern and central portion of the study area. The quality improvement in south is poor. It is suggested that by constructing large number of artificial recharge structures to trap monsoon rainwater along the northern and central part of the study area will improve the quality of groundwater remarkably. Designing of recharging wells along the southern region will result in considerable improvement both in the quality and quantity of groundwater.