Unraveling (Sub)-surface Water Dynamics in a Mining Environment: Hydrogeological and Hydrochemical Insights

Mining environments exhibit geochemically dynamic landscapes driven by geogenic and anthropogenic processes, resulting in the deterioration of groundwater and surface water quality. The hydrogeological alterations in such settings further facilitate contaminant mobility, thereby increasing the vulnerability of (sub)-surface water resources to contaminant transport. This study presents an integrated hydrogeological and hydrochemical framework to delineate contaminant pathways and understand (sub)-surface hydrochemical processes in a semi-arid mining region. To operationalize this framework, a series of electrical resistivity tomography (ERT) surveys were conducted to characterize subsurface heterogeneity and identify potential pathways for contaminant movement. The ERT survey was followed by (sub)-surface water quality analysis to understand the hydrochemical process governing water contamination. The resistivity variations in ERT profiling revealed distinct subsurface geological formations. The low resistivity values varying from 2.99 to 10 Ωm reflected aquifers saturated with a possible contaminated plume from either surface runoff or anthropogenic mining activities. The high resistivity values (>100 Ωm) corresponded to weathered formations, which serve as active sites for geogenic rock-water interactions. The entropy water quality index revealed distinct spatial variations in contaminant levels, whereas principal component analysis distinguished between anthropogenic and geogenic factors influencing water quality in the mining-impacted region. The isotopic composition of groundwater (δ²H = 3.67·δ¹⁸O – 17.09) indicated recharge from an evaporatively modified, surface-influenced source, suggesting increased susceptibility to surface-derived contamination, whereas the surface-water samples (δ²H = 5.70·δ¹⁸O – 13.94) primarily reflected evaporative enrichment. Overall, the integrated hydrogeological and hydrochemical framework is found to be effective for understanding the key subsurface processes that drive contaminant mobility and deterioration of water quality in mining regions.

Keywords: Hydrogeological alterations, Contaminant mobility, ERT profiling, Electrical resistivity tomography, Rock-water interactions