Using a discrete fractures model for studying fractured aquifers of the Achaean basement of Touba (Northwestern, Côte d'Ivoire)

The modelling of groundwater flow in a fractured network was carried out using a theoretical approach based on the geometric characteristics of the fractures in the Achaean basement of the Touba region (Ivory Coast). This study is based on structural data (fracture network) interpreted from satellite imagery, and confirmed by field surveys. The characterization of the geometric parameters (study of scale laws) and the study of network connectivity were followed by calculations of flows and equivalent induced permeability using a discrete fractures model based on several hypotheses (e.g., only fractures and fault zones are conducting and permeable; all the fractures are vertical and have the same permeability; the hydraulic gradient is applied on a square domain independent of the topography). The Touba region fractures network is a mature (fracture length distribution follows a power law) and fractal (self-similar) network. The simulated flows are strongly channelled in fractures of regional size which largely control the connectivity of the network under the above assumptions regarding the physiographic characteristics of the area and the imposed hydraulic gradient. The groundwater pathways, determined by the hydrogeologic model, seem to agree with the zones of mean and high yield. In central and western Touba, the model produced satisfactory results (partial conformability between the simulated groundwater pathways and boreholes that have mean and high yields). This result is promising with respect to the identification of the best sites for drilling high yield boreholes.