Application of Resistivity Methods for Groundwater Exploration Around Chuko, Southern Region of Ethiopia.
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Date
1998
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Addis Ababa University
Abstract
Geophysical surveys and studies were carried out in southern Ethiopia
around Chuko town for ground water exploration by the hydrogeological tearn in
the Ethiopian Institute of Geological Surveys (EIGS) during 1984 - 1985. These
data are reanalyzed from the scientific point of view. It is observed that the
apparent resistivity data at a horizon having sufficient thickness can be descnbed by
the linear equation where the slope is the same as tangent of the dip angle of the
fault.
The causes of the principles of equivalence for this particular survey area
are aquifers (and possibly aquicludes ) and this problem can be managed by fixing
the resistivity value of aquifer known from other information sources such as weDs.
The results of the inversion shows that the resistivities of all layers associated with
aquifers converges towards this fixed value without any change in the depth range
indicating the fact that it is not the number of layers but the resistivity value of
aquifer that is in the interpretation sounding curves for the ground water
exploration. From type curve analysis the assumed faults are investigated which are
identical with the ones obtained using profiling results. The type curve mapping is
powerful in zone as weD as fault mapping.
The stacked graphic plot, pseudoelectric and geoelectric section analysis
shows that the resistivity of the water bearing formations are in general greater than
40 ohm-m and these formations, which are dominated by fractured volcanic rocks
and sands of varying grain size, are most available in the eastern part of the base
line with varying depth ranges.
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Application of Resistivity Methods