Surficial Geophysical Deduction of the Geomaterial and Aquifer distributions at Ngor-Okpala local Government Area of Imo State, South Eastern Nigeria

Twenty seven vertical electrical sounding (VES) profiles surrounding four known traverses were obtained in Ngor-Okpala local government area of Imo state to examine the subsurface geomaterials and the associated groundwater potential. The VES data, constrained by borehole data, provided useful information about the subsurface hydrogeologic and lithologic conditions. From the validated interpretation, the area assessed has loamy soil, medium grained sands, well-sorted medium-grained/gravelly sands and river sand as the lithologic succession from top to the bottom of the depth penetrated. The aquifers in the area were found in the medium-grained sands and well-sorted medium-coarse-grained sands. The aquifer depth for all-season groundwater that would be devoid of draw-down can be found at a depth range of 42-50 m. The resistivity maps of selected depths exhibit sharp resistivity changes at depth due mainly to undulating subsurface topography. A map of the distribution of the k sigma-values shows that good quality groundwater can be found in most parts of the area.