Pages: (113-125 )
Abstract
Thirty Schlumberger vertical electrical soundings (VES) were carried out in Oroogun, Ogbomoso, southwestern Nigeria with a view to evaluating the groundwater potential of the area. The VES data were acquired with a resistivity meter using current electrode spacing varied from 1 to 100 m, and interpreted by partial curve matching and 1-D computer-aided forward modelling technique. Geoelectric sections, isopach maps of the aquifer units and groundwater potential maps were generated using the VES data. Results of the interpretation revealed three to four geoelectric layers defined as topsoil, lateritic layer, weathered layer and fractured/fresh bedrock with resistivity ranging from 63 to 820 Ωm, 164 to 864 Ωm, 20 to 429 Ωm and 100 to 7793 Ωm respectively. Overburden thickness varies from 7.4 to 48.9 m. The overburden is generally thin while only 27% of the study area has overburden thickness greater than 20 m. The overburden and weathered/fractured bedrock constitute the aquifer units.The groundwater potential is medium in about half of the study area. About 20% of the study area, located toward the western part, lies within high groundwater potential zone while 30% has low groundwater potential. The groundwater potential map is expected to serve as guide for groundwater development in the area.
Keywords: vertical electrical sounding, geoelectric sections, isopach map, overburden, fractured bedrock .,