Integrated geospatial, hydrochemical and isotopic assessment of groundwater recharge, dynamics and quality variations in a climate-induced coastal aquifer of Western India

This study evaluates the controls on seasonal groundwater quality changes, aquifer recharge sources and dynamics in a climate-impacted region of western India. The spatial pattern of Entropy Water Quality Index (EWQI) indicated significant water quality improvement from pre to postmonsoon. About 52.6% of the area showed poor quality in premonsoon, while nearly 50% shifted to the “good” category after the monsoon. Geochemical facies are dominated by Mg-Na-HCO 3 -Cl in both seasons. Principle Component Analysis (PCA) of groundwater indicated the dominance of evaporative concentration and anthropogenic inputs during premonsoon, but shifts toward geogenic controls during postmonsoon, with agricultural influence in both seasons. Stable isotope data confirmed the strong evaporation before the monsoon and a clear monsoonal recharge in postmonsoon. Tritium values (2–7.5 TU) support modern recharge to groundwater sources in this region. The integrated study of water quality, isotopes and geospatial tools indicated the presence of both natural and human-driven processes shaping the groundwater quality of the study region, underscoring the need for sustainable management aligned with SDG 6 and SDG 12.