The Use of the Resistivity and Magnetic Methods for the Investigation of Ground Water, Intermediate and Shallow Structures in Ajie Western Arsi Zone
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Date
2019-05-02
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Addis Ababa University
Abstract
In this study a combined geophysical data was used for groundwater controlling factors; shallow and intermediate structures in the central main Ethiopian rift. This study focused on a assessing hydrogeological conditions of the area with the controlling factors subsurface layers and structures. Two Geophysical methods were employed in this study are, Vertical electrical sounding and magnetic survey technique. Electrical sounding the sculmerger method was used to investigate for the potential the groundwater in the study area. On the other hand, magnetic survey was used to delineate geological shallow and intermediate structures which control the groundwater flow system. The geophysical survey was conducted, twe15 VES readings by using Schlumberger array along three survey lines, and above two hundred and fifty magnetic reading at about 50meter interval along 4 profiles. The field data obtained was processed and analyzed by using special computer softwares. The2D model with geological layers and resistivity values was interpreted to enhance the result. The results of the geophysical survey are presented in the form of interpreted VES curves, sliced stacked map, pseudo depth section, geoelectric section, magnetic anomaly plot and 2D model. The study result revealed four to five (6) main geoelectric layers that differ in degree of weathering and fracturing. The highly weathered and fractured ignimbrite with is the main water bearing horizon which has good groundwater potential but it is deeply layed. The aquifer thickness in the area is obtained to range between 100m and 240m. The result also shows there are sub surface structures in the area is dividing the area by several subsurface geological shallow and intermediate structures that are important for the movement and occurrence of groundwater. It seems that, some well sites can be towards the end of profile -1 and along profile -3.Further hydrogeologicaland and geophysical survey and can be recommended along the proposed sites for farther studies.
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Resistivity, Magnetic Methods, Investigation, Ground Water, Intermediate, Shallow Structures, Ajie Western, Arsi Zone