Intermontane groundwater systems of southern India: Quality assessment and controlling processes

This study assesses groundwater quality in an intermontane region of the Eastern Ghats, South India, focusing on physicochemical characteristics, heavy metal contamination, and suitability for drinking and irrigation. Groundwater samples were analysed for pH, electrical conductivity (EC), total dissolved solids (TDS), total hardness (TH), sulfate (SO₄²⁻), and toxic metals (Cd, Pb, Cr) using standardized laboratory methods. Spatial variability in water quality was mapped using ArcGIS v10.8, and the Heavy Metal Pollution Index (HPI), Heavy Metal Evaluation Index (HEI), and Water Quality Index (WQI) were applied to quantify pollution levels. Results showed that nearly 45% of samples exceeded safe limits for drinking (WQI > 100), mainly due to elevated EC (up to 4870 µS/cm), TDS (up to 3410 mg/L), TH (up to 1400 mg/L), and toxic metals above permissible standards. Hydrogeochemical analysis indicated that carbonate weathering and ion exchange are the dominant natural processes, but anthropogenic inputs, including agricultural runoff and industrial effluents, significantly increased contamination. Irrigation suitability assessment revealed critical constraints, with EC levels above 3000 µS/cm and sodium adsorption ratio (SAR) values reaching 10 at several sites, indicating risks of salinization and sodicity. Overall, the study highlights the urgent need for targeted pollution control, stricter environmental regulations, and sustainable groundwater management strategies to protect public health and agricultural productivity in this vulnerable semi-arid highland region.