Authors : M.A. Oladunjoye, A. Adefehinti and I.A. Korode
Abstract: Geological structures in crystalline basement rocks have great influence on the groundwater occurrence. If the structures are not mapped with precision, groundwater exploitation may end up being a low yield or dry holes. To assess the groundwater potential of Gbongudu community in Ibadan Southwestern Nigeria, 2-D electrical resistivity imaging and 1-D vertical electrical soundings were utilized. Wenner and Schlumberger configuration techniques were adopted for the acquisition of 2-D resistivity imaging and vertical electrical soundings, respectively. Eleven Electrical Resistivity Imaging (ERI) lines with varying lengths from 100-200 m and nine vertical electrical soundings. The 2-D field data were inverted using DIPROFWin Software while the 1-D data were plotted on a bi-log graph and interpreted using partial curve matching with suitable auxiliary charts and the result was iterated using “RESIST” Software. Three lithologic units were observed from the 2-D section which are the top layer (reworked clayey soil/compacted lateritic soil), the weathered basement (gravelling sandy-clay/clayey-sand) and the fractured/fresh basement rock while the VES revealed two to three geoelectric layers namely, topsoil, weathered layer, fractured unit and fresh basement. The weathered and the fractured basement form the aquiferous zones in the area investigated. Results of the 2-D ERI shows it is more effective in mapping weathered layer and localized fractures while the VES proved to be effective in detecting overburden thickness, basement fractures and basement topography within crystalline rocks. It was observed that groundwater occurrence within the study area is highly localized and requires detailed investigation to locate productive zones for groundwater development. Prospect areas were limited to areas with relatively thick overburden and fracture basement.
M.A. Oladunjoye, A. Adefehinti and I.A. Korode, 2018. Use of Two Dimensional Electrical Resistivity Imaging to Assess Groundwater Potential in the Basement Rock of Gbongudu Community, Southwestern Nigeria. Online Journal of Earth Sciences, 12: 8-29.