Groundwater Vulnerability Assessment in the Coastal Plain Sands of Akwa Ibom State

Groundwater in the Coastal Plain Sands aquifer of Akwa Ibom State, South South Nigeria, is extensively used for domestic and industrial water supply, but the shallow water table and high aquifer permeability characteristic of this unit render it potentially vulnerable to contamination from surface activities. This study assesses groundwater vulnerability to contamination in the Coastal Plain Sands aquifer across three local government areas of Akwa Ibom State using the DRASTIC and GOD index methods. Input parameters for DRASTIC including depth to water table, net recharge, aquifer media, soil media, topography, impact of vadose zone, and hydraulic conductivity were compiled from borehole logs, soil surveys, and field measurements. The GOD index was computed using groundwater occurrence, overall lithology of the aquifer, and depth to groundwater. Vulnerability maps were generated by spatial integration of the input parameters in a GIS environment. Nitrate concentration in groundwater samples collected from seventy boreholes was used to validate the vulnerability indices against actual contamination occurrence. The study identifies high-density residential areas in Uyo and Eket as zones of very high vulnerability coinciding with elevated nitrate levels, suggesting inadequate sanitation infrastructure as the dominant contamination driver. Findings are communicated to the Akwa Ibom State Ministry of Environment and Mineral Resources to support wellhead protection planning and sanitation investment prioritisation. Keywords: groundwater vulnerability, DRASTIC, Coastal Plain Sands, Akwa Ibom State, nitrate contamination.