Groundwater chemistry and entropy weighted water quality index of tsunami affected and ecologically sensitive coastal region of India

Quality groundwater is the most essential prerequisite for better livelihood of coastal villages and a vital resource safe living. Seawater interaction inundation modify hydro geochemical cycles leading to gross utility as challenge. Poor quality water intake causes diseases seriously affects human health. In this study, suitability shallow drinking sources (10–15 m) has been studied with focus on village in south west India (Alappad coast, Kollam, Kerala) which host huge placer mineral reserve country. This stretch good deposition Late Quaternary sediments heavy placers subjected severe seawater interactions. Mineralogical, garnet minerals comprises beaches plains Alappad. A concerted geological process where moving waves erosion, leads lowering earth's surface -is prominent fragmented land. Study critically evaluates temporal-spatial impact these an age varying climatic conditions reference beyond. Water index analysis attempted using entropy weighted (EWQI) method total 45 samples (15 season-wise). It aims ascertain choices domestic uses isolated settlers endowed estuaries, old barrier beaches. Irrigation was evaluated sodium adsorption ratio (SAR) Na%. Observed EWQ Indices (38.2 ± 14.5) post-monsoon (80% samples), (66.1 77.7) monsoon (66% (71.4 71.3) pre-monsoon (53% samples) fall excellent category. Post-monsoon favoured evidenced by WQI 80% among tested. Ca–HCO3 dominant hydrochemical type observed. The mean value iron (0.9 1.3 mg/L) exceeded permissible limit 0.3 mg/L during season due mineral-water parameters Na+ (95.9 200.7 mg/L), Cl− (173.4 510.2 EC (1559.3 2510.6 μS/cm), TDS (492.5 629.7 were observed higher ranges. Significant correlation (p < 0.05) prevailed between EWQI, parameters-conductivity (0.75), (0.59), Ca2+ (0.66), Mg2+ (0.74). Principal component (PCA) chemical accounted variance 84.2% pre-monsoon, 89.9% 82.9% post-monsoon. Groundwater influenced processes, salt intrusion, activities like fertiliser application sewage discharge. Hierarchical cluster (HCA) grouped into three clusters. Cluster 3 represents poor (13%) (EWQI ranged 32.2–192.7), 171.8–309.7). (20%) indicating 51.4–72.6). Ultimate finding that more suitable purposes selected area.