Laboratoire d’Hydrologie Appliquée, Institut National de l’Eau (INE), Université d’Abomey-Calavi, 01BP. 526 Cotonou, Benin 3Département des Sciences de la Terre, Faculté des Sciences et Techniques, Université d’Abomey-Calavi, BP : 2462 Abomey-Calavi, Benin
Prospecting for groundwater resources is a problem in the Donga Department (North-West Benin) to satisfy people's water needs. Remote sensing remains essential for the mapping of water presence indicators, which are linear structures. The present study proposes to map the major fractures of North-West Benin from Landsat-8 OLI images and to use field data to characterize them. The use of spatio-directionnel filtering methods of Sobel and gradient and the techniques of Selective Principal Components Analysis allowed the creation of the major lineaments map. The validation of these last ones was carried out by several field works (geology, hydrogeology, geomorphology and botany). These data were superimposed in a GIS. After treatment, the obtained card counts 745 major fractures. This approach allowed to discriminate three major types of fractures. Fractures marked by vegetation alignments (type A) are the most abundant and occupy 60% of the area of the Donga Department. Fractures related to geological formations (type B) occupy 20% of the area of the study area and correspond to strike-out and shearing structures. The fractures indicated by the rectilinear cornices of lateritic cuirass (type C) correspond to late faults. The study of the directional distribution of outcrop fractures shows that the major directions are N-S (27%) and NE-SO (24%). This map will serve as a background document for future hydrogeological surveys in the region.