Geo-Electric and 3D-Imaging of Groundwater Distribution along Flood Plain Deposits of River Niger at Jebba, North-Central Nigeria.

Abstract

Twenty five profiles of Vertical Electrical Sounding were obtained at Jebba area, North-central Nigeria with the aim of ascertain the nature of groundwater distribution in the area. The area is characterized by arid climate of low rainfall and high evaporation. The old alluvial plains surface is covered with a silty-sand and gravel which are subject to new reclamation. The first sedimentary cover unit < 0.5 m is draped by silty-clay causing some of the area under analysis to be water-logged. It is underlain by a sandy layer more than one meter thick beneath the surface. The geo-electric cross-sections produced from the interpreted twenty five VES data using iterative computer program revealed three to four geo-electric layers. The top most layer ranged between 5 ?m-1722 ?m and is suggestive of lateritic clay with a thickness of 0 m-1.5 m. Layer two has thickness of 1.5 m-28 m with an average apparent resistivity of 30 ?m-122 ?m and is suggestive of weathered basement layer. Layer three has a geo-electric layer of thickness between 28 m-45 m with an average apparent resistivity of between 50 ?m-350 ?m which is suggestive of partly weathered/fractured basement and fourth layer suggestive of the fresh basement. The geo-electric sections suggested two system aquifer, weathered layer aquifer system and the partly weathered/fractured basement aquifer system. These aquifer units possess largely good hydraulic characteristics and groundwater potential. This study enables the delineation of shallow aquifers, their subsurface disposition and identified promising areas for elaborate groundwater development in the area. An integration of such hydro-geophysical study with lithologic logs/drilling data would enhance accurate delineation of aquifers of the study area. Another high point of this study is the application of the leapfrog hydro software to prepare 3D Imaging of the sub-surface and to delineate areas high groundwater potentials.