Surface Water–Groundwater Interactions in a Sahelian Catchment: Exploring Hydrochemistry and Isotopes and Implications for Water Quality Management

---

Résumé

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.

Mots-clés

urface water-groundwater; hydrochemistry; stable isotopes; Sahel region; Kou basin; Burkina Faso