The hard rock area of Natham taluk, Tamil Nadu, is mainly dependent on groundwater as the main water source, and with the growing anthropogenic activities, water quality has become an issue of concern. This paper analysed 51 samples of groundwater on major physicochemical parameters to determine their applicability in drinking and irrigation purposes using Water Quality Index (WQI), irrigation indices, and geospatial methods. The WQI results indicate that 17.65% of samples fall under the excellent category, 66.67% under good, and 15.69% under poor quality, with elevated concentrations of total dissolved solids, nitrate, and fluoride observed in specific locations such as Sattambadi, Perumalai R.F., Lingavadi, Uralipatti, and Nadumandalam. Irrigation suitability assessment based on indices such as SAR, %Na, Kelly’s Ratio, and Magnesium Hazard reveals that most groundwater samples are suitable for irrigation, although a few locations exhibit moderate salinity hazards. Hydrogeochemical facies identified using the Piper diagram indicate the dominance of Ca–Mg–SO 4 –Cl type water, suggesting the influence of carbonate and evaporite mineral dissolution. Gibbs plot analysis indicates that rock–water interaction is the primary mechanism controlling groundwater chemistry, with a minor influence from evaporation. Spatial analysis using GIS highlights significant variability in groundwater quality across the study area. The results have valuable implications in groundwater resource management and also in making decisions on sustainable drinking and irrigation water utilization in semiarid hard rock areas.
Balasubramaniyan et al. (Fri,) studied this question.