Groundwater-Bearing Potential of The Permanent Site of Ajayi Crowther University, Offa- Meta, Oyo, Southwestern Nigeria

Abstract

The need to provide reliable water supply within the permanent site of Ajayi Crowther University in Oyo Town is now inevitable. This is due to the fact that there is no nearby source of potable water neither is there any existing piped town water supply scheme in this area. The present study employed resistivity geophysical methods including seven horizontal profiling (HP) to delineate probable zones with groundwater potential and sixteen vertical electrical sounding (VES) for further deeper subsurface proving of the probable zones. The field data were curved matched and iterated using WinResist software to compute the geoelectric section parameters and these were used to describe the extent of weathering and bedrock fracturing of the subsurface horizon. From the HP results, sixteen probable zones with resistivities spread between 31.4 and 342.9 Ωm were delineated for further vertical probes. VES results showed that the dominant geo- electric sequence is the 3- layer H type curve with the sub-surface units categorized into top soil, saprolite units and weathered/fractured/fresh bedrocks. The thickness of the top soil was 1.0 - 4.9 m, and that of the saprolite was between 10.1 m and 38.1 m while the resistivity of the saprolite ranged from 32.1 to 424.5 Ωm. The total regolith thickness was between 11.3 and 42.9 m with an average of 26.2 m – this is an indication of good weathering development and good potential for groundwater occurrence. The bedrock resistivities lie between 242 and 3636.5 Ωm. The resistivities of most of the underlying bedrocks at the western part and to a lower extent at the middle section of the study area were found to be less than 600 Ωm and were interpreted as fractured bedrocks. Locations underlain by fractured bedrock in conjunction with areas with thick overlying weathered units constitute the aquifer zones that represented locations with good groundwater potentials in the area. Hence, the western and the middle sections of the study area were classified to have good groundwater potential while the potential is moderate at the eastern end