VLF-EM and VES: an application to groundwater exploration in a Precambrian basement terrain SW Nigeria
Main Article Content
Abstract
In a hard rock environment with surface or near surface expression of outcrops, the use of VES only becomes difficult due to its associated problems and limitations. However, the use of VLF-EM becomes imperative in mapping basement structures relevant to groundwater development. A total of 2100 VLF-EM data plus selected VES points were covered over 7 traverses with length varying from 3000 to 4500 m. The VLF-EM result mapped basement structures relevant in groundwater development. This is further studied using VES. Results of the investigation indicate that a HKH sounding curve is obtained with a maximum of five subsurface layers comprising: the top soil, clay/sandy clay unit, the fresh basement, fractured basement and the basement bedrock. The fractured basement layer constitutes the main aquifer unit with thickness of 20-25 m. The layer resistivity and thickness ranges are 60-100 ohm-m; 40-80 ohm-m, 1600-2100 ohm-m, 250-420 ohm-m, and 2200-7500 ohm-m; and 0.3-1.2 m, 1.9-2.5 m, 16.5-22.5 m and 22-30 m for the five layers respectively. The geoelectric results compared favorably well with drilling information to above 90%. The yield of the well is 2 L/s with good recharge capability.
Article Details
Open-Access License
No Permission Required
Istituto Nazionale di Geofisica e Vulcanologia applies the Creative Commons Attribution License (CCAL) to all works we publish.
Under the CCAL, authors retain ownership of the copyright for their article, but authors allow anyone to download, reuse, reprint, modify, distribute, so long as the original authors and source are cited. No permission is required from the authors or the publishers.