Groundwater Assessment through an Integrated Approach Using GIS and Electrical Resistivity Technique: A Case Study from the Bullom Group of Sediments in Sierra Leone

Electrical Resistivity in conjunction with Geographic Information System (GIS) techniques have been widely used in groundwater resource management. In this research, Vertical Electric Sounding (VES), an Electrical Resistivity method, was integrated with GIS to delineate geo-electric characteristics and evaluate groundwater potential of the Bullom group of sediments in Sierra Leone. For this assessment, a total of 5 vertical electrical sounding stations were established within the site. The Schlumberger electrode configuration and the expanding procedure were used for data acquisition. The VES curves generated were interpreted using partial curve matching. The depth sounding interpretation results were used to generate geo-electric sections from which the aquifer was delineated. The aquifer revealed four subsurface layers which comprises of sandy topsoil, clayey sand which acts as aquitard and sandy gravel (confine aquifer) that serves as a source of portable water in the study area. A GIS model was then developed to locate the suitable groundwater prospective zones which reveals the average depth to groundwater to be between 10 m to 30 m. This research concluded that the boreholes were sited in high conductivity zones in VES layers 1, 2, 3 and 4 as they contain probable aquifers with good yield.