SCHLUMBERGER RESISTIVITY SOUNDINGS FOR GROUNDWATER EXPLORATION: A CASE STUDY OF KAJURU AREA OF NORTHERN NIGERIAN BASEMENT COMPLEX

Abstract

Geoelectric soundings using the symmetric Schlumberger configuration were carried out to investigate the groundwater potential in fifteen communities of Kajuru local government area within the Northern Nigerian Basement Complex. The project employed the acquired vertical electrical soundings (VES) data and hydrogeophysical expression of structural features and aquiferious zones to model groundwater prospects in the area. Model layers correspond to weathered, fractured and fresh basement zones of varied thickness and lithology. The VES curves obtained were predominantly KH and QH type curves. The topsoil, laterites and pebbles have thicknesses from 2-7m with a resistivity range of 2807m-3600 Ωm. Following this layer is a progression into mainly sandy clay units with a weathered denser sandier base. The thickness of the zone varies from 8-20m and resistivity range of 198-406 Ωm. The partially weathered and fractured portions of the basement have thickness ranges of 9-26m and resistivity of 106-357Ωm. The depth to fresh basement extent from 28m to 36m depending on the intensity of fracturing and weathering, it has resistivity greater than 650 Ωm. The permeable rock units are the fine-coarse sands of the weathered basement and crystalline fractures. The groundwater potentials of the sites investigated appears generally reasonable for borehole development.