EVALUATION OF GROUNDWATER POTENTIAL USING 2D ELECTRICAL RESISTIVITY IMAGING AND VERTICAL ELECTRICAL SOUNDING (VES) METHODS: CASE STUDY OF THE FEDERAL UNIVERSITY OF PETROLEUM RESOURCES, EFFURUN, DELTA STATE

Electrical resistivity method employing the 2D ERT Wenner technique and the 1-D Vertical Electrical Sounding (VES) technique using Schlumberger electrode configuration was conducted at the Federal University of Petroleum Resources Effurun, Delta state to determine the underground water potential and depth of favorable groundwater at the study location. Five (5) 2D ERT traverses lines identified as Lx1, Lx2, Lx3, Lx4 and Lx5 and seven (7) VES data (VES 1 to 7) were acquired and used to evaluate the groundwater potential at the study location. Data processing and inversion was done using Earth Imager 2D software and the WinResist-1D application. The result showed that the area is underlain by groundwater favorable layers at varying depths within the subsurface. The favorable layers for groundwater abstraction were observed in VES 1 at the third layer with resistivity of 455.1 ῼm, thickness of 33.90 m at depth of 41.90 m, in VES 2 the third layer with resistivity of 3565.90 ῼm, in VES 3 the third layer with resistivity of 1388.50 ῼm and thickness of 10.40 m at depth and the fourth layer with resistivity of 486.4 ῼm, thickness of 32.10 m at depth of 45.20 m, in VES 4, the third layer with resistivity of 2909.90 ῼm, in VES 5 the third and fourth layer with resistivities of 2315.20 ῼm and 451.5 ῼm, thickness of 31.40 m at depth of 35.70 m in VES 6 the third layer with resistivity of 822.60 ῼm, thickness of 38.0 m at depth of 51.20 m, while in VES 7 the third layer with resistivity of 4239.0 ῼm, thickness of 10.30 m at depth of 15.20 m. The VES result was correlated with the borehole section of the area where coarse sand at depth of range between 12.192 and 15.240 m was the aquifer layer. These depths were consistent with the depth of coarse sand observed in VES 3 and 7 interpretations. The result of 2D ERT inversion for lines Lx1 to Lx5 imaged a maximum depth of 17.10 m, and imaged the presence of water (saturation zone) at varying depths ranging from 8.6-17.1 m in line Lx1, 9.8-11.50 m in line Lx2, 12.80-17.10 m in line Lx3, and 9.0 m in line Lx4. The result obtained from the VES interpretation clearly indicates that the aquifers in the area lies predominantly at the third and fourth layers with depth of about 41.90 to 45.20 m and depending on the location. Therefore, it was recommended that a reliable borehole for good portable water should be sited at the location of VES 3 along line Lx3 having fine aquifers at a depth of 45.20 m in VES 3 and 12.80 m to 17.1 m along line Lx3.