Geophysical Analysis on Varthur Catchment Area, Bangalore Urban District, Karnataka, using Remote Sensing and GIS Techniques
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Abstract
Groundwater occurrence in hard rock terrains is governed by the geometry and interconnectedness of weathered and fractured zones in crystalline basement rocks (Dewandel et al., 2006; Maréchal et al., 2004). This study presents a geoelectrical investigation of the Varthur catchment, Dakshina Pinakini River Basin, Bengaluru, Karnataka, integrating Vertical Electrical Sounding (VES) with Dar Zarrouk parameter analysis and remote sensing GIS. A total of 46 VES stations were established across 284 km² using the Schlumberger configuration. Quantitative interpretation delineated a four-layer sequence comprising topsoil (ρ1: 12–65 Ω·m), weathered basement (ρ2: 22 157 Ω·m), fractured/partially weathered rock (ρ3: 84–535 Ω·m), and massive bedrock (Palacky, 1987), with weathered zone thickness (h2) ranging from 1.5–14.6 m (mean: 8.9 m). Longitudinal conductance (S: 0.09–0.51 S) indicated weak to moderate overburden protection at most stations, implying significant aquifer vulnerability (Henriet, 1976; Oladapo and Akintorinwa, 2007), while transverse resistance (T: 136.4–1581.7 Ω·m²) identified elevated groundwater potential in the southern and southeastern sectors (Niwas and Singhal, 1981; Utom et al., 2012). Structural contour analysis revealed heterogeneous basement depressions in the western and central portions. The integrated S–T interpretation demonstrates a trade-off between aquifer productivity and protective capacity typical of hard rock systems (Singhal and Gupta, 2010), providing a spatial framework for groundwater development and contamination risk management in this rapidly urbanizing catchment.
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