Unveiling the extent of salinization to delineate the potential submarine groundwater discharge zones along the North-western coast of India

Highlights: • Integrated use of hydrogeochemistry and probability distribution to identify seawater intrusion (SWI). • Probable zones of submarine groundwater discharge are identified by nullifying SWI locations. • SWI is mediated by mainly groundwater depletion, vertical groundwater mixing and evapotranspiration. • Engineering remediation is recommended for the replenishment of saline coastal aquifers. The North-West coast of India was notable for the urbanization and semiarid climate, particularly the Gujarat coastal region which was facing water crises and aquifer salinization issue. Under the light of these critical issues, the present study investigates the sources of aquifer salinization and probable location of submarine groundwater discharge (SGD) using an integrated approach of major ion chemistry, statistical techniques, and isotopic signature of groundwater (GW). The evolution of GW reveals that water facies changes from Ca²⁺-Mg²⁺-Cl⁻ to Na⁺-Cl type from the south Gujarat towards the Gulf of Khambhat. Log-normal distribution of Cl⁻ and NO₃⁻ divulges that different pollution sources influence the GW quality. Statistical findings supplemented with Isotopic signatures, ionic ratios and cross plots identified four classes of GW, which varies with degree of anthropogenic and seawater influences. Results suggested that seawater intrusion heavily influences 42% of the total GW samples, whereas 58% samples showed the probability of SGD. The study recommends the feasible locations of check dams as a remedial measure for controlling the salinization of coastal aquifer.