Hydrogeophysical characterization of aquifers in Upper Denkyira East and West Districts, Ghana

Abstract

AbstractHydrogeophysical assessment of aquifers in the Upper Denkyira East and West Districts of Ghana has been carried out for groundwater potential and protective capacity of the overburden rocks determination. The data for the study were obtained from the Regional office of Community Water and Sanitation Agency (CWSA), Cape Coast. A total of thirty-seven VES probed using a Schlumberger array with maximum current electrode spacing (AB/2) of 100 m at each point using the Abeam Terameter was used. The data were interpreted using the partial curve matching and WINRESIST computer iteration program techniques. The thickness and resistivities of the various overburden layers, basement resistivity, reflection coefficient and longitudinal conductance were used for the assessment of the groundwater potential and the protective capability of the overburden layers. The study revealed three-to-six layers with an average of four (4) layers including laterite (0.34–3.57 m); clay (0.64–8.84 m); sandy-clay (0.67–27.09 m) and slightly-to-highly weathered bedrock which includes phyllites and granite (3.09–86.89 m) that show high level of heterogeneity of electrical resistivity of the geologic materials within the study area. The weathered layers serve as the aquiferous zones. About 21.6%, 62.2%, 2.7% and 13.5% showed high, medium, low and very low potential for groundwater, respectively, with higher groundwater potentials at the western and south-eastern corner of the study area underlain by the Birimian and Tarkwaian formations, respectively, indicating that the two formations have similar groundwater potentials in the study area. The lowest groundwater potential was observed at the point underlain by the granitic intrusion. The assessment of the protective capacity of the aquifer showed very good (5%), good (27%), moderate (19%), weak (22%) and poor (27%) indicating that the study area is overlain mostly by materials of different protective capacities. This study presents information on the aquifer protective capacity evaluation by using geophysical technique and it has revealed that the Birimian formation has a good aquifer protective capacity than the Tarkwaian formation and has also confirmed the effectiveness of using geophysical techniques in ground investigation.