Investigating structural controls on groundwater potential in parts of southeastern Ghana using geophysical tools to improve access to sustainable groundwater resources

Groundwater development in crystalline basement rocks is complex due to the discrete variations in the fractures, weathered zones and other geologic constraints which determine groundwater flow. To maximize groundwater exploration in such areas, it is imperative to understand the significance of the interplay between fracture systems as well as weathered zone thicknesses. To characterize these factors that underpin groundwater access in crystalline rocks, a geophysical assessment of parts of the Pan-African Dahomeyide rocks underlying the Akatsi district and parts of the Central Tongu district in southeastern Ghana was completed. Characterization of the fracture or lineament systems together with the weathered zone thickness was done using a multi-scale approach of interpreting airborne magnetic data together with limited direct current (DC) 2D electrical resistivity tomography (2D ERT) data. Based on the magnetic signatures, linear features at different depths and of different lengths were identified with the dominant trends being NE-SW. Inversion of the resistivity data aided in defining the weathered zone thicknesses in connection with established soil types including planosols, cambisols, luvisols, solonetz, gleysols and vertisols found in the area. The combined effects of lineaments and weathered zone thicknesses as a dual-porosity model are discussed in terms of their impact on groundwater development.