Source investigation of Ikanje artesian spring in north-central Nigeria, using VLF-EM and VES geophysical techniques

Abstract

The study is aimed to examine the subsurface fracture system surrounding the Ikanje Artesian spring as regards the water-bearing zones to determine the source of the spring. The area is in a part of the basement complex of southwestern Nigeria. Using the ABEM WADI Very Low Frequency-Electromagnetic (VLF-EM) equipment, 40 profiles were established, 10 on each geographical coordinate at a 5 m inter-station gap, giving a total of 800 station positions. Four resistivity VES points were deployed for correlation purposes. Excel, Fraser Filter, and Karous-Hjelt Filter software were employed for the analysis. The Fraser Filter and Karous-Hjelt plots revealed underlying water-bearing fractures in all directions with prominence toward the south. The trend of the water-bearing fractures that links all the southern profiles indicates that the spring’s source is in the southern area. Inferred 3D conductive maps equally confirmed the highest conductivity in the southern region of the area, indicating wet fractures. The 1D pseudo sections from VES points indicated that the main aquifer linked to Ikanje artesian spring is hosted by a 64.5 m thick fractured basement, overlain by a weathered basement in the SW flank; thus the location could be most suitable for groundwater exploitation.