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Abstract

Basement rock aquifers underlie more than 20% of the earth’s surface. However, due to an inadequate understanding of fracture/fault zones, it is challenging to locate the groundwater resources in crystalline hard rock terranes. Faults, fractures, and shear zones play an important role in bedrock weathering and ultimately groundwater storage in these terranes. This present study integrates geologic structures with high-resolution 2D-resistivity imaging in understanding the factors that influenced bedrock weathering and groundwater storage in the subsurface. The results reveal the variability of weathered zone depth in different structural zones (Zone-I to Zone-IV), which are interpreted clearly from the resistivity contrasts. The variability is due to the presence of pervasive foliations, fractures, and faults. A thicker weathered zone develops when a fracture/fault overprints a pre-existing planar pervasive structure like foliations (Zone-II) as compared to zones only with faults and fractures (Zone-III). Further, the preliminary borehole discharge data also shows higher discharge in Zone-II compared to Zone-III and Zone-I, which implies a good pact between different structural features and resistivity contrasts of the subsurface. Moreover, the weathered zone thickness in these areas led to groundwater storage and possible recharge sites. Therefore, the effect of these structures on groundwater explorations cannot be ignored. This study can be readily adopted globally for mapping bedrock weathering and improving the search methodology for groundwater exploration and management, especially in water-scarce crystalline basement terranes. Also, the study also identifies solutions to one (i.e. Measurements and data; UPH 16) of the Twenty-three unsolved problems in hydrology (UPH).