Efficacy of anisotropic properties in groundwater exploration from geoelectric sounding over trap covered terrain

Abstract

Electrical resistivity study assumes a special significance for mapping aquifer in hard rock area and is also widely used in delineating the lateral and vertical distribution of sub-surface. 23 Vertical electrical soundings (VES) with Wenner electrode configuration were carried out over Chikotra basin, located in the southern part of Kolhapur district in the Deccan Volcanic Province (DVP) of Maharashtra to delineate the groundwater potential zones and anisotropic properties of fractures for sustainable groundwater development within the study area. The results illustrate that the secondary geophysical indices provide a constructive solution in delineating the fresh water aquifers in the trap covered area. The longitudinal conductance (S) value vary from 0.016 to 5.44 Ω-1, suggesting that the entire study area reveals good to weak aquifer protective capacity rating. The low value of the protective capacity in the northern and central part of the basin is due to the absence of significant amount of clay as an overburden impermeable material, thereby enhancing the percolation of contaminants into the aquifer. The large variation in the coefficient of anisotropy from 1 to 6.18 at the 23 VES data sites, suggests the anisotropic disposition of the aquifers in basaltic region. The fracture porosity inferred from the geophysical parameters and specific conductance of groundwater varies from 0.0001% to 0.556% in the study area, signifying different degrees of water saturation within the basaltic layers. The high-porosity zones corroborate with the high anisotropy values, indicating significant reserves of exploitable groundwater. This practice of analyzing VES data provided the direct solution to resolve problems in different hard rock terrains with a severe scarcity of groundwater, which has a great social impact.