Abstract
Aim/objectives: This research is geared towards integrating Vertical Electrical Soundings (VES) and Electrical Resistivity Tomography (ERT) profiles constrained with geoelectric sections and borehole logs to assess the vulnerability of the aquifer units employing Aquifer Vulnerability Indexing (AVI) method.Method: The dataset used in this study comprises of fifty VES, five ERT profiles surveyed in parts of Enugu north in Enugu state, two geoelectric sections and three borehole logs. The computer and manual interpretation of VES resistivity data using WinResist software gave values of resistivity, depth and thickness of each geoelectric layer using half current electrode spacing of 1.0 to 450.0m and maximum current electrode spacing of 900 m. 2D imaging data from the measured field resistance values were processed using RES2DINV32 version 3.71.115 software. The geoelectrical sections show the variation of resistivities with depth along transcent lines. The geohydraulic parameters were also estimated. Finding: Interpreted VES data revealed five to six geoelectric layers and fundamental parameters generated were used to estimate the values of hydraulic conductivity (s ) and hydraulic resistance (C) of the covering layers ranging from 0.010 to 0.769 mday1 and 40.47 to 8292.0 day1 respectively.This research revealed high hydraulic conductivity in the western part implying good groundwater potential with moderate to high protective capacity while areas with low hydraulic conductivity correspond to areas with high resistivity indicating little or no pore space and total devoid of water. The hydraulic resistance quantifies groundwater vulnerability using AVI and reveals that the area of study is characterized by low to high AVI with moderate AVI dominanting.Originality and novelty: The estimated geohydraulic properties from resistivity data and their spatial spread are promising and could increase the depth of knowledge on groundwater vulnerability within and around the study area. Keywords: VES; ERT; AVI; hydraulic conductivity; hydraulic resistance
Highlights
Socio-economic development depends majorly on water considering its importance on plants, animals and human activities such as agricultural industry, manufacturing industry, transportation industry, construction industry, home usage and life which cannot be overemphasized [1], [2]
The hydrogeologic unit of the area was assessed using the results from Vertical Electrical Soundings (VES) and Electrical Resistivity Tomography (ERT) profiles
The estimated aquifer vulnerability index (AVI) of the protective layers helps in evaluating the vulnerability of the study area and delineation of vulnerable zones within the study area
Summary
Socio-economic development depends majorly on water considering its importance on plants, animals and human activities such as agricultural industry, manufacturing industry, transportation industry, construction industry, home usage and life which cannot be overemphasized [1], [2]. The need for adequate, clean, safe and good quality water source in both rural and urban areas becomes necessary. Groundwater quality is generally considered to be superior to surface water[4] because of the purifying effects of the soil column as a result of the earth acting as natural sieve during the process of percolation. Nigeria is listed as one of the countries among 39 countries in the SubSahara Africa that practice open defecation[6] making ground water an unsafe source of drinking water for many areas [7]. The potential for ground water to become contaminated through human activities on the earth surface has come to lime light in recent years. There is a relatively high cost of replacing unsafe sources with bottle treated water or other measures than existing potable ground water resources[10]
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