Evaluation of Saltwater Intrusion in Some Coastal Areas in Rivers State, Nigeria

This study is to evaluate the three-dimensional hydrogeophysical and hydrochemical architecture of coastal aquifers within the Benin Formation Niger Delta, employing multimethod triangulation of two-dimensional Electrical Resistivity Tomogram (ERT), Advanced Digital Multi-Magnetic Tomogram (ADMT), Vertical Electrical Sounding (VES), and co-located groundwater hydrochemical analysis across six contiguous communities from Sama, Tema, Abalama, Buguma, Ido, and Obuama Area. Geophysical inversion resolves laterally persistent conductive zones (0.678-48.8 Ωm) interpreted as saline wedges and mineralised plumes exploiting paleo channel discontinuities and compromised borehole annuli, with pseudosection convergence substantiating robust inversion fidelity (RMS 1.4-7.6%). Hydrochemically, extreme spatial bifurcation is documented: Tema Well 2 registers electrical conductivity of 7,490 µS/cm, total dissolved solids of 3,750 mg/L, and salinity of 3,810 mg/L, whereas adjacent BH3 maintains pristine conditions (EC 529 µS/cm). The irrigation water quality index delineates a tripartite zonation from excellent to very poor, affirming that vulnerability is structurally controlled by topographic relief and aquifer confinement. Critically, the tomograms reveal encapsulation geometries wherein conductive plumes entirely bound remnant freshwater lenses, creating metastable island architectures subjected to imminent diffusive compromise. These findings affirm that coastal aquifer degradation in the Niger Delta is a process driven, structurally mediated crisis.