Hydrogeochemical and isotopic characterization of shallow groundwater in Dangbe East and West Districts, Ghana

Groundwater is a critical water resource in coastal regions of Ghana, where surface water availability is often limited and vulnerable to contamination. Understanding recharge mechanisms and hydrogeochemical evolution in shallow aquifers is essential for sustainable water resource management, particularly under increasing climatic variability and anthropogenic pressure. This study integrates hydrochemical and isotopic techniques to characterize shallow groundwater in the Dangbe East and West Districts of southeastern Ghana. A total of 48 water samples from wells, rivers, streams, and lagoons were analyzed for major ions, trace elements, and stable isotopes (δ¹⁸O, δD, and δ¹³C-DIC). Hydrogeochemical tools, including Piper and Gibbs diagrams, were used to identify dominant water types and controlling processes, while isotopic data were evaluated against the Global Meteoric Water Line (GMWL) to determine recharge sources. Groundwater is predominantly of the Na–Cl type, with cations in the order Na > Mg > Ca > K and anions Cl > SO₄ > NO₃ > HCO₃. Elevated salinity and high Cl⁻ concentrations indicate significant influence of seawater intrusion and evaporation, particularly in coastal and lagoon environments. Trace element enrichment (e.g., Sr, Fe, Mn, As) reflects strong water–rock interaction. Isotopic compositions show that most samples plot along or near the GMWL, indicating meteoric origin, while a smaller fraction exhibits evaporative enrichment and mixing with surface waters. The results demonstrate that rainfall is the dominant source of recharge to the shallow aquifer system, with groundwater chemistry primarily controlled by water–rock interaction and modified by coastal salinization and localized anthropogenic inputs. This integrated approach provides a robust basis for groundwater management in vulnerable coastal environments.