Conceptual Model of Aquifers in the Bedrock Zone of the Marahoué Watershed (Centre-West of Ivory Coast)

Abstract

Marahoué watershed, located in the Center West of Côte d’Ivoire, has experienced significant population growth in recent decades. And a major economic boom linked to intense agricultural activity and the presence of certain industries. This population growth is also accompanied by seasonal water shortages. Hence it needs to better manage the basin’s groundwater, which is a permanent resource and more resistant than surface water to climatic hazards. The objective of this study is therefore to propose a conceptual model of hydrogeological flow for the sustainable exploitation of groundwater resources in the Marahoué watershed. The establishment of the conceptual model was carried out in two stages. The first step consisted in defining the stratigraphic units. For this purpose, three units have been defined. These are the layer of alterite, the useful fissured horizon and the sound basement. The thickness of the layer of alterite varies from 0 to 80 m with an average of 26 m. As for the useful fissured horizon, its thickness is between 43 and 46.5 with an average of 45 m. In addition, the roof of the basement presents a slightly uneven morphology with a North-West, South-East dip and the altitudes are between 150 and 390 m. The second step corresponds to the phase of determining the hydrodynamic parameters. During this phase, the crack porosity, the transmissivity, the conductivity, the storage coefficient, the hydrological balance and the piezometric map were determined. Indeed, these parameters (the crack porosity, the transmissivity, the conductivity and the storage coefficient) confirm not only the heterogeneity of the medium but that the cracked horizon is sufficiently porous to be assimilated to an equivalent continuous medium during the simulation.