Integrated Electrical Resistivity Tomography and Vertical Electrical Sounding for Aquifer Delineation in Hard Rock Terrains

ABSTRACT Basaltic hard rock aquifers exhibit pronounced structural and lithological heterogeneity that complicates groundwater assessment and often leads to oversimplified assumptions of subsurface uniformity. A clear gap exists in linking geophysical measurements to process‐based understanding of vertical connectivity, storage characteristics and recharge pathways in such terrains, particularly across the Deccan traps. This study addresses this gap by integrating electrical resistivity tomography (ERT), vertical electrical sounding (VES), limited borehole lithologs and 2D/3D stratigraphic modelling to delineate the hydrostratigraphic framework of Artal sub‐watershed in southern India. Geophysical inversion outputs were transformed into volumetric stratigraphic models and evaluated using borehole control, inversion diagnostics and cross validation to assess structural fidelity and predictive reliability. The resulting 3D architecture reveals laterally variable weathered mantles that govern shallow storage and discontinuous, basement‐controlled fracture zones that influence transmissivity and vertical connectivity. Uncertainty is highest within fractured domains due to inherent geological discontinuities, whereas overall layer ordering and depth structure remain consistent. The integrated framework clarifies the hydrological processes that regulate recharge efficiency and identifies spatially explicit zones suitable for managed aquifer recharge (MAR), thereby supporting evidence‐based groundwater management and contributing to SDG‐6 targets on sustainable water management.