Evaluation of groundwater potential and aquifer protective capacity of the overburden units in trap covered Dhule district, Maharashtra

Abstract

This paper illustrates the determination of overburden protective capacity using vertical electrical resistivity sounding in the semi-arid hard rock terrain in Dhule district of Maharashtra. A total of 54 vertical electrical soundings (VES) were carried out using Schlumberger configuration with maximum electrode separation of 200m. The objective of this study was to locate groundwater potential zones and to evaluate the protective capacity of aquifers. Results reveal that the longitudinal conductance (S) value ranges from 0.07 to 13 mhos (siemens). The overburden protective capacity of the aquifers reveals a good to moderate rating at 92% of the VES sites. While 2% each represent weak and poor rating, 4% fall in the excellent category. It is further observed that VES sites located towards north at Sirpur and northern Sindkheda sub-divisions have better protection to aquifers due to thick alluvial cover deposited by Tapi River. The transverse resistance reveals higher values towards north-west, east and south-east parts of the study area. Electrical anisotropy shows a large variation ranging from 1.028 to 6.55, implying heterogeneous and anisotropic nature of the subsurface in the study area. A positive correlation is observed between the fracture porosity and electrical anisotropy, indicating the porous zones in the study area. Further, stations with low reflection coefficient revealed higher electrical anisotropy, suggesting an inverse correlation between these two parameters. These results provide reliable information about the protective capacity of the geomaterials overlying the aquiferous unit and the fracture geometry using various geophysical indices. This is vital for planning and development of prospective water resource programs and serves as a guide for groundwater pollution control in hard-rock, semi-arid regions.