The present study is aimed to assess coastal aquifer system along the sea shore area of Gulf of Mannar. An effort has been undertaken for a detailed survey of ground waters, twenty five ground water samples collected during three different seasons namely pre-monsoon, monsoon and post-monsoon. Nineteen physico, chemical and biological parameters like temperature, pH, TDS, total hardness (TH), temporary hardness (THA), permanent hardness (PHA), total alkalinity (TA), Cl-, SO₄^2-, CO₃^2-, HCO₃^-, Ca²⁺, Mg²⁺, Na⁺, K⁺, DO, BOD and COD were analyzed for collected ground water samples. The experimental results were compared with standard values as prescribed by Bureau of Indian standard (BIS) and World Health Organization (WHO). The results showed that, some of ground water samples have high hardness, EC, TDS, sodium, calcium, chloride, DO, BOD, COD content. From this study, it is observed that, some of water samples unfit for drinking purposes due to high salt concentration. These high dissolved solids may be due to salt water intrusion. The influence of seasonal changes (Pre-monsoon, monsoon and post-monsoon) on the physico-chemical properties of the water of Gulf of Mannar shore area also investigated. This study showed that the salt concentration is found to be very high during pre-monsoon compared to other seasons, it may be due to water evaporation during pre-monsoon season.

Keywords: Ground Water; Gulf of Mannar; Physico – Chemical Analysis; Seasonal Variation; Hardness;