APPLICATION OF VERTICAL ELECTRICAL SOUNDING FOR GROUND WATER EXPLORATION AROUND BASEMENT COMPLEX TERRAIN. SOUTHWESTERN NIGERIA.

Vertical Electrical Sounding was used for identification of potential groundwater zones in Akure, Ondo state and measurements were taken using Schlumberger Configuration along the four profiles at station intervals of 10 m. A total of 53 VES were conducted with half electrode spacing (AB/2) varying from 1-150 m. This geophysical work was carried out at around Federal housing estate Akure, South-western Nigeria known to be associated with the problems of groundwater aquifer. Many of the boreholes drilled in this area are either perched or later dried-up during the dry seasons including hand-dug wells. The geoelectric sections delineated a maximum of four subsurface geological layers consisting of the top soil, weathered layer, fractured basement and fresh basement. The top soil resistivity values vary from 30.9-257 Ωm with thickness ranging from 0.3-5.1 m. The weathered layer resistivity values range from 20.2-2832.3 Ωm. Its thickness varies from 1.1 and 10.5 m. The fractured basement resistivity range from 23.9 to 570 Ωm, the thickness varies from 2.6-65.6 m. The weathered and the fractured basement constitute the main aquifer units in the study area. The fresh basement resistivity values ranges from 582-64167 Ωm. The groundwater map generated was used to classify the study area into high, medium and low groundwater potential zones. VES methods have been successfully used to evaluate the groundwater potential of the Federal Housing Estate Akure.