GEOPHYSICAL TECHNIQUES FOR AQUIFER CHARACTERISTICS - A CASE STUDY OF KCAEFT CAMPUS, MALAPPURAM KERALA

Abstract

Groundwater is the primary source of fresh water for domestic, agricultural and industrial purposes, meeting over 85 per cent of India's drinking water and 60 per cent of its irrigation requirements (World Bank, 2012). Malappuram district, where the study area is located, records a groundwater extraction stage of 67.22 per cent with seven blocks classified as semi-critical (CGWB, 2019). In this context, a geophysical investigation was undertaken at the campus of Kelappaji College of Agricultural Engineering and Food Technology (KCAEFT), Tavanur, situated at 10.85° N latitude and 75.97° E longitude, to characterise subsurface aquifer formations and assess groundwater potential. Vertical Electrical Sounding (VES) surveys were conducted at seven locations (L1–L7) across the campus using a Signal Stacking Resistivity Meter (MODEL SSR-MP-ATS) with the Wenner electrode configuration. Current electrode spacing (AB) ranged from 6 m to 60 m, and potential electrode spacing (MN) from 2 m to 20 m. Field data were interpreted using IPI2WIN software, which employs an iterative forward-modelling approach to derive true subsurface resistivity, layer thickness and depth (Mohammad et al., 2013). Subsurface lithology was classified using resistivity ranges established by Azhar et al. (2017). Interpretation of sounding curves revealed two to three distinct subsurface layers, with H, K, A and Q-type curves identified across the study area. The H-type curve at L4 (Coconut Farm), with a conductive intermediate layer of 507.9 Ω-m and a bedrock depth of 0.89 m, indicated the most favourable aquifer conditions. K-type curves at L1, L5 and L7 reflected high-resistivity lateritic or hard rock in the middle layer. The A-type curve at L2 indicated a transition from clayey topsoil to hard rock, while Q-type curves at L3 and L6 represented progressively decreasing resistivity consistent with weathered formations. The depth to bedrock across all locations ranged from 0.89 m to 14.3 m, highlighting significant subsurface heterogeneity. The study demonstrates that the electrical resistivity method combined with IPI2WIN-based interpretation is an effective tool for delineating subsurface lithology, identifying potential aquifer zones, and supporting borehole site selection and sustainable groundwater management.