Breakable geological structures and groundwater in the Koumfab catchment area of northern Togo

Abstract The Togolese government mainly uses groundwater to provide water to rural and urban populations due to the poor condition of surface waters. The Koumfab watershed, located in northern Togo (Dapaong) has a substratum composed of crystalline rocks and ancient Proterozoic sedimentary rocks, giving it a hydrogeological configuration of basements aquifers. Consequently, its groundwater potential is related to the thickness of its soil cover and the fracture networks it contains. A hydrological balance has been established at the scale of the basin and the map of the lineaments of the basin is obtained through aerial images and the numerical model of the field treated by the GIS software. Three families of lineaments are obtained and classified according to their importance. The main directions of these lineaments are N01°-N40° with a cumulative weight of 32.48% corresponding to the majority of fractures; the mean fractures correspond to N60° to N120° with a cumulative weight of 42.27% and finally the N121°-N180° and N41° -N59° are minority fractures for 24.78%. The correlation between these lineaments and drilling flows has shown that lineament lengths and their connectivity’s have a significant influence on groundwater potential (drilling rate), but it’s not the only parameter that controls the productivity of these watersheds. Lithological facies and water inflow in the depths located 40–80 m range and probably the thickness of the soils layer is, however, parameters that control the productivity and thus the hydrogeological potential of the region.