Assessment of hydrogeochemical characteristics and saltwater intrusion in selected coastal aquifers of southwestern India

The principal objective of this study is to assess the saltwater intrusion and hydrogeochemical processes that affect groundwater geochemistry in the coastal aquifers of southwestern India. Groundwater samples were collected seasonally and the physico-chemical parameters determined on-site. Major ions were determined in the laboratory. Hydrochemical diagrams, ionic ratios, and multivariate statistical analysis were adopted for understanding the groundwater chemistry. Gibbs plot identified that rock-water interaction and evaporation were the mechanisms regulating hydrogeochemistry. Ionic ratios have shown that coastal wells were contaminated with saltwater intrusion during the pre-monsoon season. Hierarchical cluster analysis classified the samples based on their quality; sample clusters with high NO₃⁻ were in densely populated areas, whereas sample clusters with moderate salt content in the coastal areas. Another cluster showed high concentrations of salts, typically the zones of saltwater intrusion. The study concludes that influence of seasons, geogenic and anthropogenic factors contribute to the heterogeneous chemistry of groundwater.