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

Olateju O Bayewu,Stephen O Ariyo,Moroof O Oloruntola,Julius O Fatoba,Ganiyu O Mosuro,Temitope A Laniyan

doi:10.1007/s13201-017-0623-4

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.

Highlights

IntroductionGroundwater potential mapping is relatively complex due largely to highly variable nature of the geological terrain (Kellgren 2002: Anbazhagan et al 2011) extensive hydrogeological investigations are required in basement complex environment to understand groundwater conditions (Solomon and Quiel 2006; Balamurugan et al 2008; Pradhan 2009). Evans and Myers 1990; Sener et al 2005; Singh and Singh 2009; Sharma and Kujur 2012 all noted that several methods commonly adopted in delineating groundwater potential depending on the available data which include remote sensing and Geological Information System(GIS)
Two geophysical methods were used for this work; the very low frequency electromagnetic (VLF-EM) and vertical electrical sounding (VES)
The combination of electromagnetic profiling and vertical electrical resistivity surveys in the study area has contributed to a better understanding of the groundwater occurrence in this part of basement complex of Southwestern Nigeria

Summary

Introduction

Groundwater potential mapping is relatively complex due largely to highly variable nature of the geological terrain (Kellgren 2002: Anbazhagan et al 2011) extensive hydrogeological investigations are required in basement complex environment to understand groundwater conditions (Solomon and Quiel 2006; Balamurugan et al 2008; Pradhan 2009). Evans and Myers 1990; Sener et al 2005; Singh and Singh 2009; Sharma and Kujur 2012 all noted that several methods commonly adopted in delineating groundwater potential depending on the available data which include remote sensing and Geological Information System(GIS). Several statistical methods can be adopted for groundwater mapping where adequate information on different influencing parameters to groundwater accumulation and movement are available These include frequency ratio (Davoodi et al 2013), multi-criteria decision evaluation (Murthy and Mamo 2009; Kumar et al 2014), logistic regression model (Ozdemir 2011), weights-of-evidence model (Ozdemir 2011; Pourtaghi and Pourghasemi 2014), random forest model (Rahmati et al 2016 Naghibi et al 2016), maximum entropy model (Rahmati et al 2016), boosted regression tree (Naghibi et al 2016; Naghibi and Pourghasemi 2015), classification and regression tree (Naghibi et al 2016), multivariate adaptive regression spline model (Zabihi et al 2016), certainty factor model (Zabihi et al 2016), evidential belief function (Pourghasemi and Beheshtirad 2015; Naghibi and Pourghasemi 2015), and generalized linear model (Naghibi and Pourghasemi 2015). The geophysical survey is employed to determine geoelectric parameters of formations, identify aquifer units and determine its depth and lateral extent (Telford et al 1976)

Objectives

Methods

Results

Conclusion