Hydrochemical characterization and geospatial analysis of pre-monsoon groundwater in the Khapri watershed, Dangs district, Western India

This study assessed the quality of pre-monsoon groundwater in the Khapri watershed of Dangs district, Gujarat, India, for drinking and irrigation purposes. Forty-five groundwater samples were analyzed for pH (6.9–8.5), electrical conductivity (208–624 µS/cm), total dissolved solids (112–285 mg/L), total hardness (88.8–245 mg/L), total alkalinity (112–285 mg/L) major cations and anions. Among the major cations, calcium ranged from 19.5 to 56 mg/L and magnesium from 1.1 to 40 mg/L; sodium (1–13.98 mg/L) and potassium (0.04–3.26 mg/L) concentrations were consistently low. For anions, bicarbonate was dominant (122–285 mg/L), followed by chloride (9.1–59 mg/L), sulphate (0.7–31 mg/L), and nitrate (0.1–6.6 mg/L). Nearly all samples met Bureau of Indian Standards thresholds for drinking, except some with permissible but not desirable levels of hardness and alkalinity. Hydrochemical facies analysis found groundwater to be of Ca-HCO₃ type, with weathering of silicate minerals as the principal geochemical process. Irrigation suitability indices (SAR, RSC, Kelley’s ratio) indicated excellent water quality for agriculture. These findings provide crucial baseline data, revealing that rock weathering primarily controls groundwater chemistry in the study area, with minimal evidence of anthropogenic contamination.