ABSTRACT
Groundwater investigation using Vertical Electrical Sounding (VES) and 2D Electrical Imaging was carried out at Abudu, Orhionwon Local Government Area, Edo State, Nigeria, with the aim of evaluating the groundwater potential of the study area.
The analysis of four geoelectric sections generated from the integration of interpreted VES results reveals four to six geoelectric layers which corresponds to topsoil, sandy clay, clayey sand, clay, lateritic sand, sandstone and sand. The topsoil has layer thickness of 0.6 to 0.8 m and resistivity value within range of 65.4 ohm-m and 565.4 ohm-m, while the sandy clay has layer thickness of 4.5 to 12.2 m and resistivity value ranging from 130.0 to 174.6 ohm-m .The lateritic sand has layer thickness ranging from 1.0 to 86.8 m and resistivity values ranging from 724.0 to 5615.9 ohm-m. The sandstone has resistivity values ranging from 6364.1 to 7517.2 ohm-m and only one detectable thickness value of 38.0 m in VES 19. The clayey sand has resistivity value of 65.4 ohm-m and thickness of 3.3 m. The clay has resistivity values of 23.1 and 36.1 ohm-m and thickness values of 1.6 and 3.0 m.
The study reveals that sand in VES 8, 9, 10, 12, 13, 14, 16, 17, 19 and 20 has resistivity values ranging from 124.1 to 832.8 ohm-m with layer thickness values ranging from 1.9 – 8.7 m. The sand is at the upper layer (second layer). It is shallow and prone to pollution. The sand in VES 1, 2, 3, 6, 7, 8, 9, 11, 12, 15, 17 and 20 has resistivity value between 130.0 and 885.4 ohm-m and thickness ranging from 3.8 to 54.7 m, which is in the mid layer( third and fourth). It is a good groundwater source. However, the sand in the bottom layer(fifth to seventh) delineated in VES 1, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 and 19 with resisistivity values ranging from 201.0 to 1416.8 ohm-m have thicknesses that could not be determined. It is indicative of the best aquifer unit for ground water exploitation.
