Evaluation of groundwater quality for irrigation purposes in hard rock terrain of Southern India using water quality indices modelling

Industrial effluent discharge threatens both agricultural productivity and drinking water quality by depleting groundwater, contaminating surface water and demanding high-quality irrigation water. This study evaluates the influence of urbanization and agricultural activities on the groundwater quality in Perundurai, focusing on its suitability for both drinking and agriculture. A total fourty samples of groundwater were randomly taken from bore wells. The principal cations and anions were analyzed revealed their dominance order: Na > Ca > Mg > K and Cl > SO4 > F > NO3. The water quality index (WQI) analysis found that around 89% samples are unsuitable for drinking. The PI value indicates that 2% samples have poor permeability and elevated risk of waterlogging make it unsuitable for field use. Analysis of the Piper diagram reveals the dominance of alkaline earth cations (Ca, Mg) over alkali metals (Na, K) and weak acids (HCO3, CO3) over strong acids (Cl, SO4), indicating specific hydrogeochemical facies. From the US salinity diagram (USSL), C4S1 samples (30%) exhibit low alkalinity but a hazardous high salinity which impairs their capacity to retain water. Wilcox classification identified that 27% samples exhibit potential limitations for irrigation due to elevated sodium content. Contamination of groundwater due to ion leaching, sewage discharge and runoff is a significant environmental concern with potential health implications.