Hydrogeophysical Analysis of Vertical Electrical Soundings for Groundwater Potential and Aquifer Vulnerability Evaluation in the Federal Capital Territory, Abuja, Nigeria

Abstract

A report from the United Nations indicates that groundwater accounts for 26% of the world's renewable freshwater and is critical for over 2.5 billion people. Expanding groundwater exploitation and management is essential to obtaining universal access to clean water and meeting the 2030 Sustainable Development Goals (SDGs), especially in Nigeria's capital, Abuja. The Water shortage in the region is caused by population increase and urbanization, with most of the potable water coming from hand-dug wells and boreholes. This study aims to identify Abuja's groundwater potential and aquifer vulnerability zones by utilizing Hydrogeophysical methodology in the form of Vertical Electrical Sounding (VES) and Geographic Information System (GIS). Geologically, the area is dominated by Precambrian rocks and sedimentary formations, including critical lithologic units such as Older Granites, Metasediments/Metavolcanics, Migmatite-Gneiss Complex, and Nupe Sandstones. VES data were acquired from 823 sites using the Schlumberger electrode configuration with maximum electrode spacing (AB/2) of 100m and processed with IPI2Win software to determine the subsurface geoelectrical layers. Crucial parameters such as Depth to Bedrock (DB), the Dar-Zarrouk Parameters (DZP), and layer resistivity were determined. Vulnerability assessment was carried out using longitudinal conductance. Consequently, most of the study area indicates moderate protective capacity. The Reflection Coefficient (RC) varies from -0.996 to 0.999, while the protective capacity ranges from poor (<0.10) to very good (5-10). Based on the DB and RC, the groundwater potential zone of the area was determined. Very low (DB < 13m and RC < 0.8), Low (DB < 13m and RC > 0.8), Moderate (DB ≥ 13m and RC > 0.8), High (DB ≥ 13m and RC < 0.8) and Very High (DB ≥ 30m and RC < 0.8). Maps were generated in the QGIS environment using the Kriging interpolation method. This result will promote sustainable management of groundwater in the study area.