People in the semi-arid region of central Burkina Faso rely heavily on groundwater resources from basement rock aquifers for potable uses. In this study, the hydrogeochemical processes that control groundwater quality and contribute to better water resource management were characterised using major ion geochemistry, the calculation of water quality indices, and through the use of spatial geostatistical analysis. A total of 360 groundwater samples were collected in hand-pumped borewells. The overall low total dissolved solids of the groundwater indicates a fast recharge regime during the rainy season. Generally, the groundwater was circumneutral to alkaline in nature with dominant Ca2++Mg2+ and HCO3− concentrations. Based on the calculated water quality indices, most of the borewells sampled produced groundwater that was suitable for human consumption. However, a few borewells exhibited high As and F− concentrations that exceeded drinking water permissible limits. The high As concentrations were likely derived from weathering of volcano-sedimentary rocks, whereas, those of F− appeared to be from granitic rocks. Bivariate plots showed that geochemical processes such as silicate weathering, mineral dissolution and precipitation, ion exchange together with evapotranspiration were the primary factors infuencing the groundwater solute acquisition. In addition, desorption and ion exchange under alkaline pH conditions could enhance As and F− enrichment in the groundwater. Spatial distribution maps of ionic strength and electrical conductivity identifed the northern sector of the study area as the groundwater recharge areas, which should require protection and a periodic groundwater monitoring plan. The fndings of this study may help decision-makers in setting up suitable groundwater quality management strategies and selecting locations for future borewell development in this semi-arid environment and fractured crystalline aquifers.

Water quality index · Basement aquifer · Hydrogeochemistry · Semi-arid region