Hydrogeophysical Study using Vertical Electrical Sounding for Groundwater Potential of Kwara Polytechnic, Ilorin, Kwara State, Nigeria

Hydrogeophysical study involving the use of vertical electrical sounding (VES) technique was carried out in Kwara Polytechnic, Ilorin, Kwara State, Nigeria with the aim of determining its geo-electric parameters and groundwater potential. A total of fourteen (14) VES points were investigated across the study area using Schlumberger electrode configuration, with half electrode separation (AB/2) varying from 1 to 150 m. The depth to subsurface layers, their thicknesses and aquifer characteristics were inferred with the electrical resistivity method. Three to five lithologic units were identified in the study from the quantitative interpretation of the VES data using curve matching with Orellana-Mooney master curves and modeling with WinResist 1.0^TM software. These include: topsoil (124-1418 Ωm), lateritic layer (4905 Ωm), weathered basement (46-1650 Ωm) partly weathered basement (2599 Ωm), fractured basement(11-68 Ωm) and fresh bedrock (556-14715 Ωm) which were predominantly of the ‘QH’ curve type (35.7%), followed by ‘H’ type (28.6%), other curve types include: ‘KH’ (21.4%), ‘HA’ (7.1%) and ‘HKH’ (7.1%). The weathered, partly weathered and fractured basement constituted the main aquifer units. The depths to fresh bedrock at the chosen VES locations vary from 5.6 to 17.2 m with a mean value of 11.1 m in the study area. Generally, the overburden at the central to the northeastern region is shallow (<9 m), while the rest of the study area is relatively thicker (10-17.5 m). In the basement terrain, the areas having thick overburden overlying fractures zones favour groundwater prospectivity. This study is expected to assist in future planning of groundwater resources.