Groundwater Investigation by the Electrical Resistivity Method in El-Gof, Moyale
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Date
1997-06
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Addis Ababa Universty
Abstract
This paper describes the Resistivity Survey carried out in EI-Gof area located some
38 km north of Moyale town in the Southern Borena region to locate and delineate a buried
river channel which are of utmost importance in the siting of high yielding, more successful
boreholes and in better understanding ofthe hydrogeology of buried valley aquifers.
Sixteen resistivity soundings using the schlumberger array with maximum AB/2
spread of 330 m were carried out. along three profile lines each I km long at an' average line
spacing of 200 m, and a YES interval of 150 m along the profiles.
All the field data were corrected for the effect of the first distance of l'vIN spacing on
resistivity values and then interpreted by using curve matching and an automatic iterative
computer software program "SEV". During the interpretation process information from
borehole data were also used and were found to be quite useful to refine the interpretation
results.
Based on the results of the model interpretations of the sounding curves and from
the measured apparent resistivity value, the respective geoelectric and pseudo-section of the
area were constructed. The results obtained from these sections indicate on the average
about five geoelectricallayers and areas of low and high resistivity values.
The low resistivity structures outlined at discrete locations In the NE and SW part
are interpreted as the buried channel and the zone of high resistivity in the NW and SE part
of the area correspond to shallow depth to the bed rock.
The buried channel is characterized by undulations with shallower and deeper
sections. The deeper part of the burled channel is found in the SW part of the survey area
which are likely to con!.'lin thick succession of sand and gravel deposits. These low
resistivity areas were therefore chosen for water well drilling (borehole).
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Keywords
EI-Gof area