The Bishoftu Crater Lakes, located on the western shoulder of the main Ethiopian Riftrncan provide a sedimentary record, which has regis!ered the changes in the balancernbetween precipitation input and evaporative water loss. However, groundwater fluxesrnmay reduce sensitivity of the lakes to a change climate.rnIn order to test the possibility to use the lakes as paleohydrometers, the modem balancernbetween precipitation, evaporation and groundwater flux has been determined.rnIn the Bishoftu area where hardrock form the terrain geochemical and isotope massrnbalance has been found suitable to be used to constrain the water budget. Although stablernisotopes of oxygen and deuterium as aid in quantifying water balance of the lakes havernlimitations due to the lack of measurement of environmental parameters such as h, E, I1E ;rnthe same approach has been found appropriate for this study.rnThe varying hydrology of the Bishoftu crater lakes has provided a suitable base forrndetermining water budget using stable isotope method without reverting to thernmeasurement of environmental parameters. Accordingly the lakes have been foundrnsuitable for quantitative isotope hydrology and quantitative reconstruction ofrnpaleoclimate from lake carbonate records.rnOf the existing five crater lakes, lake Hora, lake Arenguade and lake Kilole are leastrnaffected by groundwater outflow while lake Babogaya and lake Bishoftu are morerninfluenced by groundwater outflow. The hydrology of lake Kilole is recently influencedrnby the diversion of the Mojo river into the lake. Geochemical mass balance results showrnthat lake Arenguade might be affected by geothermal water flux . Of all crater lakes, lakernHora is therefore selected as the most suitable for paleoclimate studies.