Geophysical Investigations for Groundwater Potential Assessment and Mapping Structures for possible connections between Lakes Langano and Shala, Main Ethiopian Rift
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Date
2008-12
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Addis Ababa Universty
Abstract
A low-lying narrow corridor covers the region between the two major lakes in the Main
Ethiopian Rift-Lakes Langano and Shala. Owing to the differences in surface elevation
between the two lakes and the fact that the region is affected by tectonism, the presence
of possible subsurface rift structures and flow of fluids between the lakes has been
postulated.
Geophysical surveys, involving electrical resistivity, gravity and magnetic surveys have
been carried out over the corridor to verify the presence of these structures. Three
traverses, approximately selected to cross the area have been used for surveys. Nine VES
points, 105 gravity and about 181 magnetic data have been collected and analyzed. The
results are presented in the form of electrical pseudosections and geoelectricsections and
also anomaly plots and modeled sections and interpreted to verify the presence of such
features within the corridor.
From the electrical survey data analysis it is seen that corridor between the two lakes is
represented by an extensive low resistivity response region which is believed to result
from a highly saturated subsurface horizon. The electrical survey has also mapped the
presence of structures whose orientation makes them a candidate to act as fluid paths
between the lakes. The gravity and magnetic data have been modeled together to depict
the lateral and depth variations in density and magnetic susceptibility. These results also
show the presence of structures that could act as paths for interchange of fluids between
the two lakes.
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Langano and Shala