Geogenic controls on groundwater chemistry and drinking water quality index (DWQI) evaluation in semi-arid Mahendragarh district, Haryana

Groundwater quality assessment in semi-arid regions remains understudied despite growing dependence on limited subsurface resources and increasing salinization risks. In Mahendergarh district, Haryana an area along the Aravalli ranges with scarce surface water availability systematic evaluations integrating geochemical analysis and GIS-based spatial modelling are lacking. This study addresses this gap by assessing the suitability of groundwater for drinking purposes using the Drinking Water Quality Index (DWQI). Sixteen physicochemical parameters were analysed, and results revealed that only 3.84 % of samples fell within the excellent category, 50 % good, 30.76 % poor, 11.53 % very poor, and 3.84 % unsuitable for drinking. The deterioration of groundwater quality in poor to unsuitable categories was primarily due to high salinity, posing potential health risks if consumed without treatment. Gibbs plots indicate dominant rock–water interaction with clear evaporative enrichment in high TDS zones. Piper facies mainly fall under mixed Ca–Mg–HCO₃⁻ and Na–Cl types, reflecting complex lithological controls and evaporative concentration. Hydrogeochemical interpretation reveals that silicate weathering, evaporite dissolution, carbonate weathering, fracture zones, and mineralogical influences are the principal processes influencing the groundwater chemistry of the study area. Health-risk implications highlight fluoride toxicity, salinity hazards, and nitrate related risks. This first comprehensive DWQI-based assessment supported by GIS mapping provides critical insights for continuous monitoring and region-specific management strategies to ensure safe and sustainable drinking water supply.