Hydrogeophysical Characterization of Aquifers in Parts of Central Cross River State, Nigeria: Insights from the Ikom-Mamfe Embayment

Groundwater is the primary source of potable water in Central Cross River State, Nigeria. This study investigates the hydrogeological and hydrogeophysical characterization of aquifers to optimize groundwater extraction in parts of the Ikom-Mamfe embayment. The research aims to evaluate the aquifer systems, address potential challenges and contamination risks limiting potable water exploration and exploitation, and propose sustainable groundwater management strategies for ensuring water availability and quality. To achieve these objectives, hydrogeological and hydrogeophysical methods were integrated to enhance groundwater exploration, mitigate contamination risks, and support sustainable water resource management. Key aquifer properties were assessed to determine groundwater availability, utilizing geophysical techniques such as Vertical Electrical Sounding (VES) and Electrical Resistivity Tomography (ERT) to delineate aquifer boundaries and identify zones with high groundwater potential. A multidisciplinary approach incorporating geophysical surveys, borehole data analysis, and GIS-based spatial mapping was employed. Field investigations at 35 VES locations identified two principal aquifer systems. The first, the Eze-Aku Sandstone aquifer, is located on the western and northwestern flanks, covering Ekori, Ugep, and most of Abi Local Government Area (LGA). The second, the Asu River Sandstone and Limestone aquifer, spans Abini, Adim, Idomi, Mkpani, Nko, Lebang, and Inyima in Yakurr LGA, as well as Ofat, Ofodua, and other parts of Obubra LGA. Substantial variations were observed in aquifer resistivity (9.5 to 446.5 Ωm), thickness (1.1 to 111.3 m), and depth (1.1 to 119.7 m). Transmissivity values peaked at 67.82 m²/day in high-potential zones, demonstrating a strong correlation between groundwater availability and geological formations. The study further revealed the presence of shallow aquifers (<30 m) and deeper aquifers (>60 m), with the latter exhibiting higher yields and better protective capacity. Emphasizing the importance of strategic groundwater management, this study recommends prioritizing deep aquifer drilling in high-transmissivity zones. The findings provide valuable insights for policymakers, hydrologists, and water resource managers, contributing to the broader goal of sustainable groundwater development in Central Cross River State.