Beyond the cone of depression: Multi-aquifer system response to long-term mine drainage in a structurally controlled setting

Understanding the spatial extent and variability of groundwater drawdown induced by mine drainage remains a challenge in structurally complex hydrogeological settings. In multi-aquifer systems, where aquifers are vertically and laterally compartmentalized, classical models of the cone of depression often fail to capture real-world dynamics. This study analyses over three decades of piezometric monitoring data from a multi-aquifer system affected by porphyry open-pit mining in southern Poland. The system comprises Permian, Jurassic and Quaternary aquifers, with distinct structural and hydrogeological characteristics. This study shows that long-term mine drainage causes strongly directional and anisotropic drawdown, concentrated within the fractured Permian laccolith. In contrast, the Jurassic and Quaternary aquifers remain mostly unaffected, except in areas where structural and lithological conditions allow vertical or lateral hydraulic connectivity — such as fault-guided pathways, hydrogeological windows or zones of direct overlying contact. The findings demonstrate that the extent of mine drainage influence on groundwater systems is governed by multiple factors and exhibits strong directional variability, depending on the geological structure, the continuity of aquitards, and anisotropy of groundwater flow controlled by fault zones. The results illustrate how long-term piezometric monitoring can detect spatially constrained groundwater responses in compartmentalized multi-aquifer systems and improve the evaluation of mine drainage impact in geologically complex settings.