ELECTRICAL RESISTIVITY INVESTIGATION OF GROUNDWATER PROSPECT IN IRRUA, EDO STATE, NIGERIA

ABSTRACT Water resources is vital for human existence, hence this study is conducted in Irrua, Esan Central LGA, Edo State, Nigeria, where rapid population growth and seasonal surface-water scarcity have increased dependence on boreholes. Vertical Electrical Sounding (VES) using the Schlumberger array was employed at a selected site to delineate subsurface lithology and aquifer zones. Processing of the acquired data was achieved with the use of IPI2Win software. The results revealed a 9-layer geo-electric models with sandy clay topsoil at the depth of 0.5 m with resistivity of 405 Ωm and thickness of 0.5m. The second layer at the depth of 1.2m and thickness of 0.7m and resistivity of 565Ωm is compose of clayey sand. Clay is found at the depth of 3.02m having thickness of 1.8m and resistivity of 174Ωm. it is evident that groundwater cannot be exploited in the first three layers. Within layers 6 and 7 are weathered and fractured rocks where groundwater can be exploited and is found within depths 98 – 282m beneath the surface, having thickness of 161m. The resistivity of these layers is ≥7000Ωm. It is recommended that boreholes be drilled to the depth of at least 98m beneath the surface to exploit abundant groundwater in wet and dry seasons. It is also recommended that proper geophysical studies be conducted in the environs to ascertain the exact depth of confined aquifer.