Location of Prolific Groundwater-Bearing Zones Using 2D Resistivity Imaging and Electrical Sounding Geophysical Methods within the Premises of Ajayi Crowther University Oyo, Southwestern, Nigeria

Abstract

Due to the need to provide potable water for the residents within the premises of Ajayi Crowther University, search for groundwater was conducted by integrating two-dimensional tomography (2-D) and the vertical electrical resistivity geophysical methods to delineate prolific groundwater zones within the basement setting of the study area.  From the six inverted 2-D imaging results, probable conductive units representing groundwater zones - with resistivity between 4 and 177 ?m extending to a depth of 12.4 m were established across the study area. The delineated areas were sounded to reveal the extent of regolith and bedrock characteristics. The sounding results revealed three main geo-electric models namely QH, KH and H curve types. The resistivities of the weathered layers ranged from 13.1 to 156.4 ?m and the lithology were interpreted as clayey to clayey-sand. The total thickness of the regolith ranged between 7.8 and 40.8 m and the bedrock resistivities were between 48.3 and 756 ?m. The bedrock resistivity showed that the bedrock is significantly fractured. The fractured zones occurred at an average depth of 22.8 m below the ground surface. These lithologic sequences largely support the development of prolific wells, particularly at the southeastern part of the University premises where thick regolith overlies fractured bedrock.