Journal of Geography, Environment and Earth Science International

This work addresses important problems with groundwater sustainability in coastal farming areas, where seawater intrusion compromises the quality of irrigation water. The study gives real-world examples of how hydrochemical levels change with the seasons, uses the usual AICRP categorization for irrigation appropriateness, and identifies areas in Thiruchendur taluk that are at high risk. Its GIS-based technique and block-by-block analysis give policymakers and farmers useful information on how to use climate-resilient water management methods. The results are very important for semi-arid areas around the world that are experiencing salinity problems because of climate change and excessive extraction. The groundwater quality was assessed by collecting 43 ground water samples during pre as well as post monsoon season and suitability of irrigation water was established based on AICRP classification. All the groundwater samples were analysed for pH, EC, anions (CO₃, HCO₃, Cl^-, SO₄^2-) and cations (Ca²⁺, Mg²⁺, K⁺ and Na⁺). The pH of the groundwaters of Thiruchendur taluk indicated that there was no much variation in pH of water samples collected during pre and post monsoon seasons. However, there was a wide variation noticed in EC values of groundwater, between blocks and seasons. The well waters of Thiruchendur and Udangudi blocks were of Na-Mg-Ca and Cl^- SO_4- HCO₃ whereas, the groundwaters of Alwarthirunagari block were of Na- Ca-Mg and Cl^- HCO₃ ^- - SO₄ type. In higher salinity range, sodium was associated mainly with chloride and sulphate. It is concluded that most of the well waters in Thiruchendur and Udangudi blocks are intruded with sea water and are of poor in quality. The well waters Alwarthirunagari block are likely to be vulnerable to intrusion. The well waters of Thiruchendur and Udangudi blocks should be considered seriously since the quality parameters are nearer to the composition of sea water in sodium chloride and magnesium sulphate combination. The water samples of Alwarthirunagari block fall near composition of sea water in sodium chloride combination and they may get affected by sea water intrusion after sometime. According to the AICRP suitability classification, during the pre-monsoon season, 51%, 23%, 19%, and 7% of the water samples from the entire study area were categorized as good, high SAR saline, marginally saline, and saline, respectively. In contrast, during the post-monsoon season, 65% of the samples were classified as good.