Assessing Groundwater Potential Zones in Basement Complex Terrain Using Resistivity Depth Soundings: A Case of Challenge and Oluyole in Ibadan, Southwestern Nigeria

Purpose: This study aims to delineate groundwater potential zones in basement complex terrain using resistivity depth surroundings. Design/Methodology/Approach: A total of forty Vertical Electrical Soundings (VES) were conducted along five traverses in Challenge and Oluyole localities in Ibadan (southwestern Nigeria) using a Schlumberger electrode array with maximum half electrode spacing of 150m. Measurements were acquired using JAK 6000 Terrameter. The field curves obtained from the soundings were interpreted using partial curve matching and iteratively by WinGlink computer software with output as one -dimensional sounding curves showing resistivity and depth of the subsurface layers. Research Findings: Results delineated three to four geo-electric layers. These include the surface layer topsoil with resistivity ranging from 40.42 to 933.82 Ohm.m and thickness in the range of 0.31 to 3.83m, an intercalation of clay and sand, the weathered and fractured basements constituting the aquifer with thickness of about 6.9 to 11.9m and the fresh bedrock, characterized by resistivity value of 780 to 970 Ohm.m. The geo-electric sections and the isopach maps of the overburden revealed areas of thin and thick overburdens. The areas of thick overburden (materials above the bedrock) are priority areas for possible groundwater developments. Also, the iso-resistivity maps showing the resistivity distribution of the aquifer layers had proven useful in mapping promising areas for groundwater