GEO-ELECTRICAL INVESTIGATION OF GROUNDWATER POTENTIAL ZONES OF GASSOL L.G.A USING ELECTRICAL RESISTIVITY METHOD

Abstract Geophysical investigation of groundwater potential of Gassol L.G.A. Taraba state, Nigeria was carried out using electrical resistivity method ERM with the aim of evaluating the seasonal variation/change in boreholes water of the study area. A total of twenty five (25) vertical electrical sounding VES were conducted with maximum electrode spacing of 200 m for deeper aquifer depth investigation due to the hydrogeology of the area. The primary geoelectrical field data (apparent resistivity and strata thickness) were acquired using ABEM SAS 1000 Terameter and interpreted using Interpex software. The result revealed five (5) subsurface geoelectrical layers: topsoil, sandy-clay, clayed-sand, laterite, sandstone (aquifer) and consolidated sandstone. The resistivity values of the VES points were mostly low in the sedimentary terrain except in VES 16, 17, 18, 19, 20, 22 and 25. The resistivity and thickness values range from 0.186 Ωm to 9536.500 Ωm and 0.208 m – 80.760 m. Thickness of the aquifer stratum only does not determine the groundwater potential rather the porosity and permeability of this thick layer. Depth to aquifer range from 3.300 m to 93.700 m while the resistivity values of the aquifer ranged from 1.320 to 6463.500 Ωm with an unconfined aquifer presence in VES 2, 4, 9, 10, 11, 12, 14, 16, 22 and 25 where the resistivity of the strata below the unconfined aquifers range from 0.186 Ωm to 86.390 Ωm. The seasonal change/variation in the groundwater potential of the study area is due to the depth of the unconfined aquifer used for drilling instead of the confined aquifer depth. Hydrogeological study and Proper geoelectrical resistivity survey with wide electrodes spacing (> 200 m) for deeper aquifer depth information should be conducted so to prevent seasonal variation/change of the groundwater potential from boreholes.