Estimation of aquifer hydraulic parameters from geoelectrical method—a case study of Yenagoa and environs, Southern Nigeria

Abstract

Knowledge of water transmitting properties of an aquifer is crucial for successful groundwater development and management practices in an area. In this study, the determination of aquifer hydraulic characteristics at Yenagoa and environs from Dar Zarrouk parameters was carried out using 14 vertical electrical sounding data (VES) and information from existing boreholes. The Schlumberger electrode configuration was employed for the field data acquisition with a maximum half electrode separation (AB/2) ranging between 100 and 350 m. The VES data were interpreted using 1D inversion technique software (1X1D, Interpex, USA). A maximum of four geoelectric layers were delineated and the aquifer is characterized by loose sand with resistivity ranging from 136.1 to 828.6 Ωm and thickness of 8.3–97.6 m. Using the VES results and water resistivity, porosity was determined using modified Archie’s equation. The hydraulic conductivity (K) values obtained from three reference boreholes were combined with the electrical resistivity obtained from the respective nearby VES stations to determine a diagnostic constant (Kρ). The resulting relation was interpreted with Dar Zarrouk parameters to infer the hydraulic conductivity (K) and transmissivity (T) variations at vertical electrical sounding locations, where K values are unknown. The results indicate that porosity varies between 0.09 and 0.32. The hydraulic conductivities range from 0.8 × 10−4 to 6.6 × 10−4 m/s while the transmissivity values vary between 1.1 × 10−3 and 29.6 × 10−3 m2/s. The high transmissivity values are consistent with the aquifer being unconsolidated with fine–medium–coarse sands.