Hydrogeological and Hydrogeochemical Impacts of Limestone Mining on Groundwater in the Kallar River Basin, South India

ABSTRACT Limestone mining is a major contributor to cement production in South India's Ariyalur region. However, its impact on regional hydrogeological systems, particularly, the Kallar River and adjacent groundwater reserves, requires further investigation. This study employs an integrated approach combining groundwater table elevation data, hydrodynamics, hydrogeochemical analysis, and geospatial systems to evaluate the effects of mining activities. The Kallar River's flow direction is found to be opposite to the dip of the limestone beds. The presence of marl (CaCO 3 + clay) occasionally induces seepages and slope failures in the mines, though not at a significant rate. The shows a semiconfined to confined aquifer system with limestone formations of low permeability and limited water yield. The groundwater samples (May 2024, 33 samples) assessed for water quality showed pH is within the limits and a significant proportion of samples exceeded permissible limits for TDS (27.27%), Na + (39.39%), K + (18.18%), Ca 2+ (3.03%), Mg 2+ (6.06%), HCO 3 − (12.12%), Cl − (15.15%), SO 4 2− (12.12%), and NO 3 − (24.24%). Hydrogeochemical analysis using Piper and Gibbs plots indicates a dominance of Ca–Mg–Cl–SO 4 type water, governed by rock–water interactions and anthropogenic influences. The Nitrate Pollution Index and classified 49% of samples as Clean, and WAWQI classified over 52% of samples as safe for human consumption. Overall, minimal environmental deterioration was noted, with limited hydrological connectivity between the Kallar River and adjacent mine sites. The study recommends ecological restoration measures and the construction of protective embankments to ensure the sustainability of groundwater resources over a longer period in this sensitive limestone terrain.