1D and 2D Electrical Resistivity Investigations to Identify Potential Groundwater Resources in the Hard Rock Aquifers

Hard rock aquifers develop significant groundwater potentials under favorable secondary porosity such as in fracture and fissures. However, identification of those zones is difficult due to their hydrogeological heterogeneities. The electrical resistivity methods are promising tools to identify the potential groundwater zones. In the present study, 1D and 2D electrical resistivity methods in the form of vertical electrical resistivity (VES) and electrical resistivity tomography (ERT) have been deployed for identifying potential groundwater zones in the Koppal district, Karnataka. The comparison of 1D and 2D resistivity results indicated that top soil, weathering zone, fissured and fractured zone and hard rock possessing resistivity values respectively <23, <230, <400 and >2000 ohm m. The low resistivity value <490 ohm m below hard rock in the area indicates the possibility of fracture zone underlying the hard rock. The weathered and fissured zone of 30 m thick is identified by a resistivity range of ~80 ohm m indicates a good groundwater potential in the study area. The location having weathering thickness of 10–20 m has been recommended for bore well drilling in the study which may yield about 200 m³/day.