Geophysical Evaluation of Groundwater Potentials Using Electrical Resistivity Method at Umunede.

Abstract

Understanding subsurface geo-electrical characteristics is essential for effective groundwater exploration and sustainable management. This study investigates the subsurface lithology and groundwater potential of Umunede using the Vertical Electrical Sounding (VES) technique with the Schlumberger array. Five VES stations were occupied within the study area, and the acquired data were subjected to quantitative interpretation through curve matching, using standard model curves, namely AA, KH, KH, and HKH. The data were further analyzed qualitatively using IP2Win software,the interpreted geoelectric sections revealed between four and six subsurface layers.The first geoelectric layer exhibited resistivity values ranging from 20.3 Ωm to 491 Ωm, with thicknesses varying between 0.5 m and 6.33 m. The second layer recorded resistivity values ranging from 111 Ωm to 1000 Ωm. Its thickness varied from 0.507 m to 9.53 m, while depths ranged from 1.01 m to 10.5 m. Based on the resistivity characteristics, the lithology of this layer was interpreted as clay, fine sand, and medium-to-coarse sand. The third layer consists of clay, fine sand, and medium-to-coarse sand. showed resistivity values ranging from 30.8 Ωm to 3485 Ωm with thicknesses ranging between 4.51 m and 55.2 m, while depths extended from 5.52 m to 65.7 m. Similarly, the fourth layer exhibited resistivity values ranging from 71.8 Ωm to 1247 Ωm, with thicknesses varying from 15.5 m to 98.6 m and depths ranging from 26 m to 164 m. The lithological units identified within this layer also comprise clay, fine sand, and medium-to-coarse sand. The fifth layer records resistivity values ranging from 184 Ωm to 10,763 Ωm. The thickness extends from 41 m about 120 m to infinite in some of the locations, while the depth to the layer ranges from 161 m to infinity. The layer with low resistivity is considered as potential aquifer zones while the higher resistivity is considered as coarse to gravel sediments without conductive fluids. The sixth geoelectric layer, identified only in VES 1 locations, exhibits resistivity values ranging from 254 Ωm. The lithological interpretation of layer five and six is fine to coarse sand with conductivity fluid potentials considered as aquifer zones. This aquifer zones of fine sand layer extends from approximately 43 m to 160 m depth which is in conformity and correlates with well log and lithological information obtained from nearby borehole records.
The results provide important information for groundwater development and sustainable water resource management in the area. Overall, the study presents a detailed geoelectrical and hydrogeological characterization of Umunede and offers valuable guidance for future groundwater exploration and exploitation