Hydrochemical evaluation of the strip aquifer in Srivaikundam region, Southern India: implications for drinking and irrigation

The present study focuses on understanding the groundwater geochemistry and hydrochemical characteristics of the Srivaikundam region, Tamil Nadu, with special concern on seasonal and spatial variations in groundwater quality. Groundwater samples were collected during the pre-monsoon (2021) and post-monsoon (2022) seasons, and required water quality parameters were analyzed, including pH, total dissolved solids (TDS), electrical conductivity, and concentrations of major ions such as sodium (Na⁺), calcium (Ca2⁺), magnesium (Mg2⁺), chloride (Cl⁻), bicarbonate (HCO₃⁻), and sulfate (SO₄2⁻). Further ionic ratios, such as Na + /Cl⁻ and Ca2⁺/Mg2⁺, helped to characterize the groundwater quality to understand the ion exchange occurring in areas affected by seawater intrusion. The Gibbs diagram revealed that groundwater chemistry is primarily controlled by rock-water interactions, while the ionic ratios confirmed the significant influence of marine water mixing in the coastal aquifers. In addition to that, the study highlights the role of the strip aquifer system in regulating groundwater flow and storage, which influences the seasonal variations in water quality. The strip aquifer system, consisting of both unconfined and semi-confined aquifers, is highly vulnerable based on the impacts of anthropogenic activities and reflected in the elevated concentrations of salts and other ions. According to the WHO 2017 guidelines, certain areas exhibited high levels of TDS, chloride, and magnesium, which alarm potential risks related to salinity and pollution, particularly due to the effects of human activities in the study region. This study exhibits the need for continuous monitoring and the adoption of effective groundwater management strategies in the study region to mitigate the impacts of seawater intrusion and pollution on the water quality of the study region.