Application of Integrated Geophysical Techniques to Map Groundwater Potential Zones and Geological Structures for Irrigation Purpose at ‘Humbo-Larena’ Plain, Wolaita Zone- Ethiopia
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Date
2021-05-28
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Addis Ababa University
Abstract
Combined geophysical techniques, i.e. electrical resistivity and magnetic methods, were carried out on an area of volcanic and volcano-sedimentary rocks in “Larena-Plain” at the western margin of the Southern Main Ethiopian Rift (SMER), as part of groundwater resource investigation to be used for irrigation purposes. The depth and extent of the potential groundwater aquifer were examined and mapped using the electrical resistivity (VES) technique, and the geological structures and lithological contacts responsible for groundwater flow and accumulation were revealed and mapped by using the magnetic method. Fourteen VES points were carried out over five profile lines and more than 240 magnetic data point readings distributed along the VES lines and at random points were collected and processed using different software. Additionally, apriori information/data from nearby boreholes were combined with the geophysical results for constraining the interpretation of the results.
According to the investigation outputs, there are two-stage aquifers in the study area: a deeper fractured ignimbrite and volcanoclastic-sediment aquifer covered by the shallow weathered ignimbrite aquifer. The depth to these aquifers and their distribution over the area are mapped. From thew combined results, the geological structures in the area mapped with the survey are generally aligned in NNE-SSW orientation. In addition to locating preferential areas of borehole sinking for groundwater exploitation, the study provides useful information that can be used to develop a much broader understanding of the nature of groundwater resource in the area and their relationship with the local geology.
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Keywords
Electrical Resistivity, Magnetic Survey, Groundwater Potential, Aquifers, Irrigation