ETUDE HYDROGEOLOGIQUE ET GEOCHIMIQUE DE LA BORDURE SUD-EST DU BASSIN SEDIMENTAIRE DE TAOUDENI (BURKINA FASO - MALI) - ESSAI DE MODELISATION

The southwestern area of Burkina Faso shares with the south of Mali, a transbondary aquiferous system. The understanding of groundwater flow in this large scale is confronted to the absence of reliable piezometric data. Yet this knowledge is necessary for better management of groundwater resources. The lack of data is largely due to the poor quality of topographic leveling. Various approaches combining isotopic techniques, hydrodynamic and geochemistry coupled to a test of modeling are used to understand the hydrogeology of this vast sedimentary basin. The chemical and isotopic studies give a homogeneous facies, which do not release convincing elements to consider the existence of an individualized underground circulation between the various geological formations. The southeastern basin of Taoudéni contains water which is renewed slowly. This weakness of recharge is also confirmed by hydrogeological modeling. That compromises for the future, the economical development of the area. In spite of the coherence of these various approaches, the question of the aquiferous individualization remains. This work is based on the hypothesis on a hydraulic continuity of the various rocks of the series.