Geophysical Based Groundwater Potential Zone Mapping: Perspectives and Inferences from Lisana Area along the Guder River, Western Margin of the Central Main Ethiopian Rift

Abstract

Esubalew Yehualaw and Tigistu Haile

Vertical electrical soundings and magnetic data were used to map the groundwater aquifer system in the Lisana area along the Guder River, northeast of Hosanna town, near the western margin of the Central Main Ethiopian Rift. The surveys were used to map a potential aquifer zone and investigate the groundwater potential for the current and future development of the resource in the Lisana area. The VES data were used to map the depth of a potential aquifer zone and its distribution over the area. The magnetic survey was used to delineate contacts between lithologic units and geological structures. Two-dimensional magnetic forward modeling and one-dimensional electrical modeling were used to identify fractures and lithological units containing potential groundwater. The magnetic and electrical resistivity modeling indicated that a potential aquifer occurs at a depth range from 115m to 142m. The potential aquifer occurs within weathered and fractured ignimbrite and a pumice layer containing sandy soil. This latter lithological unit is the main water-bearing horizon.

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