Geophysical Delineation of the Groundwater Potentials in a Basement Complex Terrain: A Case Study of Imope and Environs, Southwestern Nigeria.

Abstract

Vertical Electrical Sounding (VES) has been used as a tool to study the groundwater potentials exploration pattern of Imope, Igaran, Aparaki and Idofe villages, in southwestern Nigeria. A total number of eighty VES stations were established on the study areas covering 4,375,000m2 using the schlumberger configuration with electrodes spacing varying from 50 to 120m. The surveys were carried out on equal grids of 250 by 250m. Two to four lithological sections were inferred from the study areas. These are the Top soil, Lateritic Horizon, Clayey/sandy clay Horizon, and Weathered/Fresh Basement. The thicknesses of these horizons vary from 0.4-1.5m, 0-17.5m, 0 -39.1m for the top soil, lateritic layer and the clayey/sandy clay horizon respectively. The resistivity values range from 15.2-1,700 Ohm-m for top soil, 271-2,769.1 Ohm-m for lateritic horizon, 1.8-197.4 Ohm-m for the clayey/sandy clay horizon, and 337-15,300 Ohm-m for the weathered/fracture/fresh basement. Isoresistivity map of the basement and Isopach map of the overburden were plotted. Areas with thick overburden and fractured basement have been identified with high potentials for groundwater exploration.