Productivity of Fissured Aquifers from Precambrian Basement of San Pedro (Southwestern of Côte d’Ivoire)

Abstract

This study focuses on characterization of hard-rock aquifers in South Western Côte d’Ivoire where previous quantitative hydrogeological studies were not common. San Pedro is localized in South-Western Côte d'Ivoire where the basement is dominated by folded and fissured crystalline rocks. Several years ago, many drinking water supply initiatives were performed in this study area considering its particular geographical location and hydrological trumps. This study aims to contribute to the best knowledge of hydrogeological potentialities of this basement pointing to reduce doubtful quality surface water using. The database incorporated satellite radar image and reports of boreholes. The methodological approach was based on remote sensing, fracture characterizing and pumping tests. Treatment of satellite image highlighted 271 fractures ranged between 2.11 and 39.37 km. Rock mass permeability due to fractures fluctuated between 2.35E-07 and 8.13E-06 m.s-1. Spatial distribution of aquifers permeability due to fractures has highlighted three theoretical groundwater flow paths. Water yields delivered from aquifers of gneiss, granodiorite and migmatite are higher than those delivered from the aquifer of mica schist and granite. The productivity of hard-rock aquifers did not exclusively depend on fracturing density and thicknesses of weathered layers. It is also influenced by the positioning of boreholes on fractures nodes and the structure of bedrocks. Presents results have provided a guideline in searching potential zones of high quantity and best quality drinking water. These results are encouraging because they contribute to creating a Spatial Hydrogeological Information System for groundwater exploitation and management in South Western Côte d’Ivoire.