Geophysical studies of groundwater potential of parts of Etim Ekpo local government area of Akwa Ibom State, Nigeria

Abstract

A vertical electrical sounding (VES) utilizing the Schlumberger electrode configuration has been used to investigate the groundwater resource potential of some villages in Etim Ekpo local government area of Nigeria. Data was acquired using a SAS 300B model of ABEM terrameter. Current electrode separation varied from 600-800m. Results show that the sampled subsurface can be approximated by a 3-5 layer subsurface structure. The first layer is conducting topsoil with an average resistivity of 339.5Wm and average thickness of 2.75m. The second layer has a mean resistivity of 2886.5Wm and average thickness of 6m and was interpreted to be a lateritic sand layer. The third layer was interpreted to be a medium sand layer with a mean resistivity 3921.6Wm and is 8.7Wm thick. The fourth layer that was interpreted to be an aquifer has a mean resistivity of 6790Wm and is located at a mean depth of 18.5m below the surface. This layer consists of medium coarse grained (gravely) sands. This layer was not detected in the eastern side of the study area. The fifth layer that was interpreted to be a sandstone layer has a mean resistivity of 40,373.5Wm. The thickness of this layer and some parts of the fourth layer could not be determined by the maximum current electrode separation employed in the field.

Keywords: Etim Ekpo, aquifer, gravelly sand, resistivity and thickness

Nigerian Journal of Physics Vol. 18 (1) 2006: pp. 39-44