Hydrology and Hydrochemistry of Bishoftu Crater Lakes (Ethiopia)
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Date
1999-06
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Addis Ababa Universty
Abstract
The Bishoftu Crater Lakes, located on the western shoulder of the main Ethiopian Rift
can provide a sedimentary record, which has registered the changes in the balance
between precipitation input and evaporative water loss. However, groundwater fluxes
may reduce sensitivity of the lakes to a change climate.
In order to test the possibility to use the lakes as paleohydrometers, the modem balance
between precipitation, evaporation and groundwater flux has been determined.
In the Bishoftu area where hardrock form the terrain geochemical and isotope mass
balance has been found suitable to be used to constrain the water budget. Although stable
isotopes of oxygen and deuterium as aid in quantifYing water balance of the lakes have
limitations due to the lack of measurement of environmental parameters such as h, s, As ;
the same approach has been found appropriate for this study.
The varying hydrology of the Bishoftu crater lakes has provided a suitable base for
determining water budget using stable isotope method without reve11ing to the
measurement of envirorunental parameters. Accordingly the lakes have been found
suitable for quantitative isotope hydrology and quantitative reconstLUction of
paleoclimate from lake carbonate records.
Of the existing five crater lakes, lake Hora, lake Arenguade and lake Kilole are least
affected by groundwater outflow while lake Babogaya and lake Bishoftu are more
influenced by groundwater outflow. The hydrology of lake Kilole is recently influenced
by the diversion of the Mojo river into the lake. Geochemical mass balance results show
that lake Arenguade might be affected by geothermal water flux. Of all crater lakes, lake
Hora is therefore selected as the most suitable for paleoclimate studies.
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Bishoftu