Groundwater Potential Study Using Geophysical Methods Around Harbu Town, South Wollo, Ethiopia
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Date
2024-06
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Addis Ababa University
Abstract
This study was conducted in the Harbu area of the Amhara regional state, South Wollo Zone, north central Ethiopia. The present study aims to assess groundwater potential zones and aquifer characterization in the area. Vertical Electrical Sounding (VES) and magnetic methods were employed to achieve this objective. Using a Schlumberger arrangement, thirteen (13) VES points were collected with a PSI resistivity meter. Additionally, 230 magnetic data points were
collected using G600 Proton Precession Magnetometer. The magnetic survey was conducted along an east-west orientation with intervals of 100 meters along each traverse. Diurnal and IGRF corrections were applied to isolate the magnetic field arising from subsurface geological units. Subsequently, the upward continuation technique was used to differentiate between shallow and deep-seated geological formations. Various maps were generated using Oasis Montaj software, including a residual anomaly map, a tilt derivative map, and an Euler deconvolution map. A low residual magnetic anomaly was observed toward the southeast and northwest parts of the research area. Euler 3D deconvolution maps indicated variations in the depth of contact within the study area. The 2D magnetic model along the profile revealed variations in sediment thickness. To illustrate vertical and horizontal variations in apparent resistivity across the study area, a sliced stacked map was created. Additionally, geoelectric sections were prepared to provide a quantitative interpretation of apparent resistivity by integrating borehole data and VES curve models. The pseudo-depth sections showed that the central part of the study area corresponds to low apparent resistivity. The geoelectric sections indicated that the central part is characterized by thick alluvial sediment and a deep basement.
The relationship between transmissivity (T) and transverse resistance (TR) in the Harbu-Chefa graben was derived as: T = 0.6239TR - 746.18. This equation was used to extrapolate transmissivity and hydraulic conductivity of the study area.
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Keywords
Aquifer Characterization, Apparent Resistivity, Schlumberger Arrangement, Transmissivity