Groundwater is a vital resource for drinking, irrigation, and domestic use, particularly in hard-rock regions with limited surface water availability. This study assesses the groundwater quality in the western part of the hard rock terrain of Perambalur District, Tamil Nadu, India. A total of 44 groundwater samples were collected from representative wells in July 2019 and evaluated using hydrochemical and GIS-based techniques. Results show that total dissolved solids (TDS > 6%), sodium (> 5%), chloride (> 10%), and total hardness (TH > 9%) exceed permissible limits in several locations, indicating localized contamination. Major ion chemistry suggests that electrical conductivity (EC), TH, and TDS are key factors controlling drinking water suitability. The dominant hydrochemical facies include mixed Ca-Mg-Cl (39%), Ca-HCO3(29%), and Na-Cl (21%) types, primarily governed by rock weathering processes. Chloro alkaline indices (CAI-I and II) indicate the presence of ion exchange and reverse ion exchange processes. Irrigation suitability assessments using EC, Sodium Adsorption Ratio (SAR), Sodium percentage, Kelley’s Ratio (KR), Magnesium Hazard (MH), Residual Sodium Carbonate (RSC), and Permeability Index (PI) reveal that most samples are suitable for irrigation. Drinking water quality index (DWQI) classification indicates that 53% of the samples fall under excellent quality, 43% good, and 4% poor. Overall, the groundwater in the study area is generally suitable for both drinking and irrigation, although localized quality deterioration warrants continuous monitoring. This study provides a spatially integrated hydrochemical assessment of groundwater quality, explicitly quantifying the proportion of samples exceeding drinking water standards. The findings highlight priority zones requiring targeted management interventions and support evidence-based monitoring and sustainable resource planning.
Anbarasu Subramaniyan (2026) studied this question.