Application of Combined Geoelectrical Techniques for Groundwater Exploration at Federal University Gusau, Zamfara and its Environ, Northwest Nigeria

Abstract

Study’s Excerpt

• Integrated approach combining Electrical Resistivity Tomography (ERT), Natural Electric Field (NEF) method, and Vertical Electrical Sounding (VES) is used to delineate groundwater potential in the study area.
• The results revealed that the water bearing aquifers in the study area are fractured basement layers at varying depths between 15 and 105 meters.
• This research provided a robust framework for groundwater exploration in arid and geologically complex terrains.

Full Abstract

The area of study is currently facing an acute water shortage due to the dominant lithological framework that underlies the region and its fragile climate condition.  As such, this study aimed at unearthing the groundwater potential of the area using a combined three geoelectrical techniques.  Techniques such as Electrical Resistivity Tomography (ERT), Natural Electric Field (NEF) method, and Vertical Electrical Sounding (VES) were employed in the delineation of the groundwater potential of the area.  Using an ABEM SAS-4000 Resistivity meter and a PQWT-TC150 water-detector equipment, respectively.  Wennar array was employed for the conduct of ERT while Schlumberger configuration was used for VES data collection.  The measured apparent resistivity value was inputted into RES2DIV software and subjected to an inversion process to generate the resistivity structural image of the subsurface.  However, IP2WIN software was used for the VES data interpretation.  The result of the ERT method revealed two to three geoelectrical resistivity layers: an overburdened layer of topsoil/laterite with resistivity values ranging from 6.86 Ωm to 1095 Ωm and thicknesses of 1-13 meters, a weathered/fractured basement layer, interpreted as the aquifer unit, with resistivity values between 28.7 Ωm and 345 Ωm, and thicknesses ranging from 6 - 30 meters; and a fresh/slightly fractured basement layer with resistivity values from 367 Ωm to 6899 Ωm. NEF method revealed the thickness and depth of the aquiferous layer across the six profile lines to range between 15-60m, 30-90m, 15-85m, 20-80m, 45-105m, and 20-40m respectively, with points on profile five (5) identified as the most promising site with regards to groundwater development.  VES result identifies weathered and fractured layers as the major aquiferous units with resistivity values ranging from 9.965 Ωm to 9651 Ωm and 21.7 Ωm to 859 Ωm respectively with fracture thickness reaching up to 60m in some instances.  The result goes in line with the outcome of both NRF and ERT techniques.  The geological interference of this lithology on groundwater exploration reveals both the weathered overburden and fractured basement as aquiferous units in the study area.  The study identified several promising aquiferous zones at depths ranging from 15 to 105 meters, with fractured basement layers serving as primary reservoirs for groundwater development.