Hydrogeophysical Assessment of Groundwater Potential and Aquifer Protective Capacity in Some Towns in Bayelsa State, Niger Delta, Nigeria

Abstract

This study investigated the geoelectrical and hydrogeological characteristics of the aquifer system in Amassoma–Tombia, Niger Delta, using vertical electrical sounding (VES) to evaluate groundwater potential, aquifer protective capacity, and implications for sustainable groundwater development. Five VES locations (VES1–VES5) were investigated, and the interpreted parameters included aquifer resistivity, thickness, transverse resistance (TR), longitudinal conductance (S), hydraulic conductivity, and transmissivity. The results revealed considerable spatial variations in the geoelectrical properties of the subsurface. Aquifer resistivity ranged from 418 to 1,710 Ωm, while aquifer thickness varied from approximately 7.0 to 20.57 m, suggesting the predominance of sandy to sandy-clayey formations characteristic of the Niger Delta sedimentary sequence. Transverse resistance values ranged from 3,258 to 26,979 Ωm², with VES2 exhibiting the highest value and consequently representing the most favourable groundwater prospect, followed by VES3. VES4 and VES5 were identified as moderate prospects, whereas VES1 showed the lowest groundwater potential based on transverse resistance. Longitudinal conductance values ranged from 0.00478 to 0.01865 mho, placing all investigated locations within the poor protective-capacity category. This indicates that the aquifers are inadequately protected by the overlying materials and are potentially vulnerable to contamination from surface-derived pollutants. Estimated hydraulic conductivity values ranged from 0.372 to 1.386 m/day, indicating moderate permeability, while transmissivity values of 3.03–10.80 m²/day suggest generally low groundwater-transmitting capacity. Although the relatively high aquifer resistivity values suggest predominantly sandy formations and potentially favourable freshwater conditions, groundwater quality and salinity cannot be conclusively established from resistivity data alone and require hydrochemical validation. VES2 and VES3 are recommended for further groundwater exploration, subject to borehole logging and pumping tests. The poor protective capacity highlights the need for proper borehole construction, sanitary protection, and groundwater monitoring in Amassoma–Tombia.