Fracturing and Groundwater in the Koumfab Watershed in Northern Togo

The Koumfab watershed, located in the Dapaong region of northern Togo, overlies the sandstone-pelite formations of the lower megasequence of the Volta Basin and the granito-migmatitic bedrock of the south-eastern edge of the West African craton. All of these Precambrian formations have a dense network of lineaments or fractures, giving them the characteristics of discontinuous and highly exploited aquifers. The lineament map of the Koumfab watershed, obtained from aerial photographs and the digital terrain model, identifies three main families of fractures running N-S to NE-SW (N0° to N40°), NE-SW to ESE-WNW (N60° to N100°) and ESE-WNW to SE-NW (N110° to N140°). Statistical analysis and lineament-drill rate correlations highlight areas with high storage potential. This potential is mainly controlled by lithological and lineament parameters. Boreholes drilled along kilometre-long lineaments underlain by crystal and sandston formations are more productive, with generally high flow rates (Q > 5m3/h). Thanks to their fractured state, the basement formations found throughout the Koumfab catchment are major reservoirs with hydrogeological potential that are already in great demand

Fracturing and Groundwater Productivity Linkages in the Koumfab Watershed in Northern Togo

The Koumfab watershed, located in the Dapaong region of northern Togo, overlies the sandstone-pelite formations of the lower megasequence of the Volta Basin and the granito-migmatitic bedrock of the south-eastern edge of the West African Craton. All of these Precambrian formations have a dense network of lineaments or fractures, giving them the characteristics of discontinuous and highly exploited aquifers. The lineament map of the Koumfab watershed, obtained from aerial photographs and the digital terrain model, identifies three main families of fractures running N-S to NE-SW (N0° to N40°), NE-SW to ESE-WNW (N60° to N110°) and ESE-WNW to SE-NW (N120° to N180°). Analysis of the correlation between lineaments and borehole flow rates has enabled us to identify areas with high storage potential. This potential is mainly controlled by lithological and lineament parameters. Boreholes drilled along kilometre-long lineaments underlain by crystalline and sandstone formations are more productive, with generally high flow rates (Q > 5m3/h). The basement formations found throughout the Koumfab catchment are major reservoirs with hydrogeological potential that are already in great demand

Fracturing and Groundwater in the Koumfab Watershed in Northern Togo

The Koumfab watershed, located in the Dapaong region of northern Togo, overlies the sandstone-pelite formations of the lower megasequence of the Volta Basin and the granito-migmatitic bedrock of the south-eastern edge of the West African craton. All of these Precambrian formations have a dense network of lineaments or fractures, giving them the characteristics of discontinuous and highly exploited aquifers. The lineament map of the Koumfab watershed, obtained from aerial photographs and the digital terrain model, identifies three main families of fractures running N-S to NE-SW (N0° to N40°), NE-SW to ESE-WNW (N60° to N100°) and ESE-WNW to SE-NW (N110° to N140°). Statistical analysis and lineament-drill rate correlations highlight areas with high storage potential. This potential is mainly controlled by lithological and lineament parameters. Boreholes drilled along kilometre-long lineaments underlain by crystal and sandston formations are more productive, with generally high flow rates (Q > 5m3/h). Thanks to their fractured state, the basement formations found throughout the Koumfab catchment are major reservoirs with hydrogeological potential that are already in great demand

Hydrodynamic characterization of the Paleocene aquifer in the coastal sedimentary basin of Togo

The intense exploitation of shallow aquifers in the coastal basin of Togo provokes a rapid depletion of these reservoirs. The confined paleocene aquifer represents potential reserves that are yet little exploited. This paper presents the hydrodynamic characterization of this aquifer. Piezometric data established from 80 wells fluctuate between 1.17 and 3.42 m; and demonstrate the effect of pumping on groundwater level with a depression located in South-West of the study area. Major fluctuations higher than 2 m, are observed in some wells located in the North of the basin. These are a result of the recharging of the Paleocene by the shallow aquifer of the Continental terminal in the North of the basin where the two aquifers are in contact.Key words: Water table, aquifer, Paleocene, fluctuations, Togo

ACTUALISATION STRUCTURALE DE L’AQUIFÈRE DU PALÉOCÈNE DANS LE BASSIN CÔTIER DU TOGO

Groundwater is one of the main sources of drinking water to the population living in the coastal sedimentary basin of Togo. Faced with the depletion and pollution of the most accessible aquifer of the Continental terminal, it is important to find alternatives groundwater resources, exploring the potential of the deep aquifers that are little exploited this day. This study aims to improve knowledge of one of these deep aquifers and particularly the Paleocene aquifer. The Paleocene aquifer is a confined aquifer and this study focuses on its configuration, its location and its structure, based on the systematic inventory of wells and stratigraphy. Thus geological sections of North-South and West-East directions have allowed knowing the extent and geometry of this aquifer, as well as the nature of the reservoir and wall rocks. They also show that the sedimentary formations of coastal basin are organized in a monocline series dipping toward south. Different results were represented as isopach map of the reservoir and isohypse maps of upper confining bed and lower confining one. As the others formations of the basin, the wall rocks take on an air of an inclined plane towards the Atlantic Ocean. The upper confining bed elevations range from 20 m in the northern part of the basin, at -380 in the Southeast. Those of lower confining bed in the same sectors are 0 in NW and -20m in NE at -420 m in the South. This morphology of the aquifer is related to the NNW-SSE direction of extension faults that affected the crystalline basement at the opening of the Atlantic Ocean. Estimates of the reservoir thickness are between 6m to more than 50 m and are influenced by the base sands