Aquifer delineation using Vertical Electrical Sounding (VES) and correlation of borehole logs in Opolo-Epie, Yenagoa Bayelsa State, Nigeria

This study investigates the groundwater potential in Opolo-Epie, Yenagoa, Bayelsa State, Nigeria, deploying electrical sounding (VES) surveys and borehole log data analysis. Utilizing the Schlumberger electrode configuration and Terrameter SAS 1000 instrument, coupled with the Global Positioning System (GPS), three VES profiles were conducted and processed using IPI2win software and Starter 5. Key findings from the study reveal promising subsurface features and groundwater prospects. VES 1 identified distinct zones of fine to medium sand with resistivity value of 0.62-28.7 Ωm with a depth of (17.4–47.2 m) and coarse sand with resistivity value of 359 Ωm and a depth of (47.2–56.2 m). VES 2 indicated potential aquifers in the medium sand with resistivity value of 368.4 Ωm with a depth of (5.48–11.45 m) and coarse sand with resistivity value of 1089 Ωm and a depth (11.45-23.92 m), while VES 3 delineated a shallow aquifer in the fine sand layer with a resistivity of 117.4 Ωm and depth zone of (1.92–5.19 m) and a deeper, more promising aquifer in the coarse sand zone with resistivity value of 1680 Ωm and depth of (11.13–22.66 m). Borehole logging confirmed significant sand layers (3–30 meters) with potential for water storage and flow, along with a clay layer (27.1–30 meters) acting as a confining unit for underlying groundwater. The correlation between VES and borehole data revealed consistency in identifying clay layers but discrepancies in interpreting deeper aquifer zones, underscoring VES limitations in resolving thin layers. The study underscores the importance of integrating VES surveys with borehole data for a comprehensive evaluation of groundwater resources. Notably, the borehole logging-identified coarse sand layer (33.3–42.4 meters) appears to be an attractive prospect for a productive aquifer; therefore, additional research is necessary to resolve interpretational differences and determine whether clay layers exist and how thick they are in this zone.