Hydrogeochemistry and suitability assessment of surface and groundwater for drinking, irrigation, and corrosive potential in the Coastal District Porbandar of Gujarat, India

Abstract Surface and groundwater resources in semi-arid coastal regions are highly susceptible to salinity buildup, hydrochemical changes, and human activities, which compromise their usability for drinking, irrigation, and industry. This study assesses the hydrogeochemistry, spatial variation, and suitability of surface and groundwater in Gujarat's Coastal District Porbandar (CDP). A total of 81 water samples were collected during the 2024 pre-monsoon season using a 5 × 5 km 2 grid sampling method. Sixteen physicochemical parameters were analyzed following APHA (2017) standards. The hydrochemical analysis indicated dominant Na + –Cl - and mixed Ca 2+ –Mg 2+ –Cl - facies, reflecting salinity increase and advanced hydrochemical development in coastal aquifers. Higher levels of EC, TDS, Na + , Cl - , TH, and Mg 2+ were mainly found in the southern coastal areas near the Arabian Sea. The Water Quality Index (WQI) ranged from 19.36 to 727.76, showing groundwater quality from excellent to unsuitable for drinking. Irrigation indices suggested that inland aquifers are generally suitable for farming, while coastal aquifers face moderate to high salinity and sodicity risks. Industrial and corrosion indices revealed mostly corrosive groundwater traits linked to high ionic levels. Integrated analysis using Piper, Chadha, Durov, Gibbs, CAI, Mifflin, and TH–TDS diagrams indicated that seawater intrusion, evaporation, water–rock interaction, reverse ion exchange, mineral dissolution, and long residence times under semi-arid conditions mainly govern groundwater chemistry. Spatial analysis showed a progressive decline in water quality from inland recharge zones toward the southern coast. The findings emphasize the urgent need for systematic groundwater monitoring, salt management, and sustainable aquifer conservation to secure long-term water availability in western Gujarat's coastal systems.