Geophysical Mapping of the Groundwater Aquifer System in Gode Area, Northeastern Hosanna, Ethiopia
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Date
2020-06-06
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Addis Ababa University
Abstract
In this study, the basic geophysical methods are applied for mapping the groundwater aquifer system in Gode area along the Guder River, northeast of Hosanna town, near the western margin of the Central Main Ethiopian Rift. The need for additional water resources in Hosanna town and its surrounding area is highly increasing due to the growth of the population over time and the expansion of irrigation activity. This study is aimed at mapping the potential aquifer zone and investigates the groundwater potential for the current and future development of the resource at Gode area.
Geophysical methods employed in this study include, Vertical Electrical Sounding (VES) and magnetic survey techniques. Electrical sounding was used to examine and map the depth to the potential aquifer zone of the groundwater and its distribution over the area. On the other hand, magnetic survey was used to delineate contact between lithologic units and geological structures, which control the groundwater flow and storage system. The geophysical survey comprises of twelve VES readings by using Schlumberger array along six profile lines and more than four hundred (400) magnetic readings at about 10m station interval along four profiles and 20m along three random profiles.
Information from nearby boreholes were integrated to constrain the resistivity sounding survey with geological layers and various types of magnetic data plots and 2D magnetic models to enhance and visualize the results. The results of the geophysical survey are presented in the form of interpreted VES curves, pseudo depth and geoelectric sections, sliced and sliced-stacked maps, magnetic anomaly plots and 2D model section. The study result revealed that the potential aquifer in the area is obtained at depth range from 45m to 92m. This is the response of the highly weathered/ fractured ignimbrite and pumice layer with sandy soil, which is the main water-bearing horizon. Overall, in the neighborhood of four VES points, VES- 2, VES- 3, VES-10 and VES-11, shows good water bearing zones in the study area.
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Keywords
Vertical Electrical Sounding, Magnetic Survey, Aquifer, Groundwater Potential, Water Table