Beyond lineaments: Exploring the influence of weathered layers on borehole productivity in basement rocks of Burkina Faso, West Africa

Abstract In borehole siting within the basement rock aquifers of West Africa, lineament analysis has traditionally been the primary hydrogeological target, where lineaments may indicate the presence of deep geological structures. However, the limited success of groundwater borehole drilling projects suggests limitations to this approach, calling for a reassessment of its effectiveness. This study examines the role of alternative hydrogeological targets in relation to borehole productivity, focusing on weathering layers and lineaments. A comprehensive database of 2347 boreholes in Burkina Faso was developed for this purpose, revealing a strong correlation between weathered bedrock aquifer geometry and borehole productivity. The analysis indicates that the thickness of regolith and saprock strongly influence drilling success rates, regardless of whether the target yield is for hand-operated or motorized pumps. Conversely, the presence, orientation, and length of lineaments show no significant correlation with borehole productivity. The study emphasizes the need to shift focus from lineaments to weathering properties in basement aquifer exploration and highlights the dominance of a landform-regolith conceptual model over a deep geological structure model. These findings have implications for achieving universal access to drinking water and food security in West Africa’s bedrock regions.