WATER-BALANCE OF BLUE NILE RIVER BASIN IN ETHIOPIA

The Blue Nile River in Ethiopia has a drainage area of approximately 324,530 km2 and supplies nearly 84% of the water to the Nile River during highflow season, making it the main source of water for Ethiopia, Sudan, and Egypt. Relatively few analyses have been conducted on the Blue Nile River basin largely due to the lack of hydrologic data. The objective of this paper is to present existing stream-flow data for the Blue Nile River and its tributaries within the Blue Nile River basin in Ethiopia and to use that data to provide insight into the river's hydrology in Ethiopia. A monthly water-balance model was developed for this purpose. Comparisons of the predicted and observed monthly hydrographs are provided for selected subwatersheds within the Blue Nile basin. Spatial distribution of the calibrated coefficients is also discussed. Results will be useful in forecasting flows along the Blue Nile and Nile Rivers and in determining the effect of global climatic changes on continental hydrology.