Geoelectrical Viability Characterization Of Existing Boreholes
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Date
2022
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Faculty of Physical Sciences, Chukwuemeka Odumegwu Ojukwu University
Abstract
Vertical electrical sounding (VES) technique was conducted at the vicinities of 21 boreholes in the premises of the University of Ilorin; to evaluate general conditions of the boreholes. Data processing was done using the IPI2WIN package. The borehole hydraulic characteristics such as hydraulic conductivity K and transmissivity T were calculated from the interpreted VES data using the concept of Dar-Zarrouk parameters. The 2D sections obtained, indicated a maximum of four geologic equivalence of geo-electric layers namely Topsoil, Laterite, Weathered Basement, fractured basement with resistivity values ranging from 2.3 - 365.7 Ωm, 15 – 731 Ωm, 7.4 - 298 Ωm and 120 - 1500 Ωm respectively. The aquifer depth ranges between 0.91 m and 70 m and the overburden thickness ranges between 0.5 m and 7.2 m. The aquifer thickness ranges between 5.61 and 37.5 m. The materials above the aquifers showed that longitudinal conductance lies between 0.033 and 2.703 Ω-1 while transmissivity values vary from 0.0336 to 2.703 Ω-1. Borehole at VES 3 is considered to stand the best chances as it falls in the vicinity of the largest transmissivity and longitudinal conductance, deepest and thickest aquifer, which makes it free from sewage and surface contamination. The borehole at VES 6 is least suitable as the aquifer is shallow and characterized by low longitudinal conductance, implying low protective cover. This conformed to the reality on the ground, as it has been confirmed contaminated and prohibited from consumption.
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Keywords
Aquifers; Lithology, Vertical electrical sounding; Boreholes; hydraulic parameters, Research Subject Categories::NATURAL SCIENCES