Geophysical evaluation of groundwater potential in part of southwestern Basement Complex terrain of Nigeria

Abstract

The geophysical assessment of groundwater in Awa-Ilaporu, near Ago Iwoye southwestern Nigeria was carried out with the aim of delineating probable areas of high groundwater potential. The area falls within the Crystalline Basement Complex of southwestern Nigeria which is predominantly underlain by banded gneiss, granite gneiss and pegmatite. The geophysical investigation involves the very low frequency electromagnetic (VLF-EM) and Vertical Electrical Sounding (VES) methods. The VLF-EM survey was at 10 m interval along eight traverses ranging between 290 and 700 m in length using ABEM WADI VLF-EM unit. The VLF-EM survey was used to delineate areas with conductive/fractured zones. Twenty-three VES surveys were carried out with the use of Campus Ohmega resistivity meter at different location and at locations areas delineated as high conductive areas by VLF-EM survey. The result of VLF-EM survey along its traverse was used in delineating high conductive/fractured zones, it is, however, in agreement with the delineation of the VES survey. The VES results showed 3-4 geoelectric layers inferred as sandy topsoil, sandy clay, clayey and fractured/fresh basement. The combination of these two methods, therefore, helped in resolving the prospecting location for the groundwater yield in the study area.

Groundwater Exploration in Aaba Residential Area of Akure, Nigeria

“…This work has provided reliable information on the application of electrical resistivity method in groundwater exploration, which will be indispensable for developing an efficient water supply schemes and groundwater success rate in the study area. The subsurface layers are composed of three (3) and four (4) layer-earth models which is in agreement with groundwater exploration studies from Basement terrain in southwestern Nigeria such as Mohammed et al (2012), Sunmonu et al (2012), Adepelumi et al (2013), Abudulawal et al (2015), Sunmonu et al (2016), and Bayewu et al (2017). The overburden thickness varied from 4.2 to 47.1 m. Weathered layer and fractured bedrock constitute the aquifer units in Aaba.…”

“…The weathered rocks or fractured bedrocks are the prospects for groundwater in the PreCambrian basement, limestones and sandstones are the aquifers in the consolidated sedimentary environment, the aquifers in the unconsolidated sediments are composed of gravels and sands, while the fracture zones with the lava flow and palaeosoils are the major housing for groundwater in the volcanic rock settings (MacDonald and Davies, 2000). Groundwater potential mapping in basement terrain is complex due to the geological nature of the terrain, especially where aquifers are compartmentalized (Sunmonu et al, 2012;Abudulawal et al, 2015;Bayewu et al, 2017). Identification of fractures in the bedrock and/or thick overburden, as well as the degree of pore spaces and interconnectivity of the subsurface rocks have been described as the most relevant variables to understand groundwater accumulation in PreCambrian basement terrain (Adagunodo et al, 2013a;Adelusi et al, 2014;Akinrinade and Adesina, 2016).…”

Aquifer Potential Assessment in Termites Manifested Locales Using Geo-Electrical and Surface Hydraulic Measurement Parameters

“…In terms of geology, the study area is situated within the basement complex of central Nigeria with three major distinguishable lithological units, namely, the Precambrian migmatitic gneisses, Upper Proterozoic schist and Lower Paleozoic older granites [27,28], with sporadic occurrences of pegmatites and quartz dykes. As with many basement complex environments, groundwater occurrence is highly variable and occurs only in the weathered and fractured bedrock aquifers [29,30,31]. Aquifers in this region are recharged by direct rainfall infiltration and infiltration through stream and lateral subsurface flows [32].…”

Do Termitaria Indicate the Presence of Groundwater? A Case Study of Hydrogeophysical Investigation on a Land Parcel with Termite Activity

“…Aquifer systems in the basement complex environment are highly complex, very localized and have a high degree of vertical and lateral inhomogeneity resulting in abstracting structures (e.g., boreholes and wells) exhibiting highly variable yields at close distances [ 42 , 43 ]. Most communities located within basement complex terrains are usually confronted with challenges of groundwater supply inadequacies, which can be improved by more robust investigations and the incorporation of features/structures that serve as biomarkers.…”