ELECTRICAL RESISTIVITY STUDIES FOR GROUNDWATER EXPLORATION IN THE TILGANGA RIVER BASIN OF WALAWA, SHIRALA BLOCK OF SANGLI DISTRICT, MAHARASHTRA, INDIA

Abstract

A geophysical survey was carried out in the Tilganga River basin located in the northwestern region of the Sangli district, Maharashtra, utilizing the electrical resistivity method. Eighteen vertical electrical soundings (VES) were conducted to identify potential groundwater zones and to assess the thickness of the weathered formations that influence the groundwater dynamics of aquifers within alluvial deposits and trap rock. The interpretation of the VES data was performed using the IP2IWIN software, which facilitated the creation of layered models for each sounding through curve matching techniques. The study identified four distinct strata. The first layer exhibited resistivity values ranging from 2.6 ohm-m to 140 ohm-m, with thickness measurements between 0.2 m and 0.9 m. The second layer displayed resistivity values from 2.1 ohm-m to 29.33 ohm-m. For the third layer, resistivity varied from 2.75 ohm-m to 33.9 ohm-m, with thicknesses ranging from 5.2 m to 52.2 m. The fourth layer showed significantly high resistivity, reaching up to 949 ohm-m from the village of Mahadevwadi to Karmale and Rethare Dharan. The KH curve type was observed in 30% of the VES locations, while KQ and HK types were noted in 20% of the sites. Results from VES 2 and 8 indicated high resistivity values in the cross-section analysis. Pseudo cross-sections and resistivity maps were generated using IPI2WIN software. The resistivity data from VES 9 and VES 10 revealed the presence of hard compact basalts at depths of 13 m and 20 m, respectively. Additionally, VES 2 and 8 indicated high resistivity zones at depths ranging from 4 m to 20 m. The findings from the VES were compared with existing borehole and tube well logging data for validation.