Integrated Hydrogeochemical, Isotopic, and Geophysical Assessment of Groundwater Salinization Processes in the Samba Dia Coastal Aquifer (Senegal)

This study provides a detailed assessment of groundwater salinization in the Quaternary aquifer of the Samba Dia region, Senegal, using an integrated approach that combines hydrochemical, stable isotopic (δ2H, δ18O), and electrical resistivity tomography (ERT) techniques. Fourteen high-resolution ERT profiles, along with comprehensive chemical and isotopic analyses, were performed to identify the main causes of salinity and their spatial distribution. Results show that groundwater salinization in the area is primarily driven by three mechanisms: seawater intrusion, surface salt leaching, and ion exchange. Hydrochemical facies evolution diagrams, ionic ratios, and isotopic signatures helped differentiate marine-influenced zones from inland salinization areas. ERT imaging also mapped the three-dimensional extent and geometry of saline interfaces, confirming zone-specific mixing of seawater and freshwater. The findings indicate that salinization of the coastal aquifer has worsened over the past twenty years, mainly due to human activities and climate variability. This study recommends a sustainable monitoring strategy to support aquifer management, focusing on accurately identifying vulnerable zones and enabling adaptive resource planning in semi-arid Senegal.