SURFACE WATER AVAILABILITY AND DEMAND FOR THE CURRENT AND FUTURE CLIMATE CONDITIONS IN WOIBO RIVER CATCHMENT

Abstract

Ethiopia has abundant surface water resources, which could be appropriately utilized to enhance socioeconomic development of the country, but only small fraction of these potentials are utilized to accomplish the national economic and social development goals of the country. Nowadays, the government of Ethiopia has committed to increase the utilization of surface water resources. However, sustainable development can be achieved by careful utilization of its existing water resources supported by research works which may take into account the emerging challenges like population growth and climate change. This study investigates a scenario analysis to assess surface water availability and demand for the current and future climate conditions in Woibo river catchment, Omo Gibe sub-catchment. CORDEX-Africa data outputs of HadGEM2-ES for Woibo catchment were selected under representative concentration pathways (RCP2.6, RCP4.5 and RCP8.5) scenarios to make future projections. Bias correction was carried out to relate model outputs and observed datasets. The Soil and Water Assessment Tool (SWAT) was employed to model the available water in the study area. On the other hand, Water Evaluation and Planning (WEAP) model has been used to allocate the available water for the various sectors using the monthly based data in both the demand side and supply sides and by priority setting situation for demand sites. The reference period used for the simulation ranges from 1992-2015 while the future scenario period ranges from 2016- 2045. The available water in the baseline period was computed to be 351.6 MCM. The water demand for the reference period was 63.3 MCM. Further, the available water in the future period will decrease and estimated to be 293.32 MCM. The annual average water demand for the future period is increasing from 63.3 MCM to 145.93 MCM of the historical period. This shows that critical management approaches are needed to meet the increasing demand with the dwindling supply of water so that water stress shall not take place in the future