Geoelectrical signatures for detecting water-bearing zones in a micro-watershed of granitic terrain from Southern India

Abstract

This communication represents the application of geoelectrical signatures such as Dar-Zarrouk parameters, namely longitudinal conductance (S) and transverse resistance (T), which play a vital role in deciphering subsurface geometry and detect water-bearing zones in hard rock area. A micro-watershed is situated in granite terrain of Southern India, where the variation of bedrock depth and location of water-bearing zones are identified using these signatures, and achieved from the results of 47 Vertical Electrical Soundings (VESs) data. Pumping wells are recommended for the drilling, and the high yielded wells are confirmed in the water-bearing zones. The observed borehole lithology is very closely correlated with the interpreted geoelectric layer parameters. It indicates that the water-bearing zones exit in highly weathered zones having a resistivity range of 50–100 Ω-m, and 100–300 Ω-m in fractured granites at 12 to 22 m depths. The estimated T and S-values reveal the conductive mediums within the host granitic rock, whereas low S and comparatively high T might be indicative possible water-bearing/shear zone. The aquifer properties at the selective wells are compared to the aquifer potentiality. The high permeability values have been observed to confirm the presence of a shear zone, which is more productive for providing a good yielding bore well. Therefore, this approach could be replicated for groundwater exploration in any hard rock terrain.