The Sahel Transboundary Taoudéni Basin, covering about 20% of Burkina Faso, hosts vital aquifers critical for water security and development. Effective groundwater monitoring is essential for sustainable resource management. In the Kou sub-basin, groundwater quality assessment is increasingly important. This study integrates hydrochemistry, water stable isotopes (δ18O, δ2H), GIS, and multivariate statistics to understand subsurface geochemical processes. A total of 48 samples—43 groundwater and 5 surface water—were analyzed for 19 hydrochemical parameters and isotopes. In surface water, δ18O ranged from −5.96‰ to −5.09‰, and δ2H from −37.65‰ to −29.15‰. In groundwater, δ18O ranged from −5.93‰ to −4.39‰, and δ2H from −34.62‰ to −25.05‰. The spatial distribution of δ18O and δ2H was mapped using inverse distance weighted (IDW) interpolation in ArcGIS 10.8. A δ2H vs. δ18O plot showed groundwater values clustered near the Global Meteoric Water Line, indicating minimal evaporation during recharge. Groundwater chemistry was dominated by Ca2+ > Na+ > Mg2+ > K+ and HCO3− > NO3− > Cl− > SO42−. Key hydrogeochemical processes include water–rock interaction (leaching, weathering, ion exchange) and anthropogenic pollution. Isotopic signatures reveal heterogeneous recharge sources and aquifer connectivity. These findings enhance the understanding of water sources and geochemical processes in the Kou basin, supporting informed groundwater resource management.
Ouédraogo et al. (Wed,) studied this question.