Evaluation of the Water Balance in Blue Nile River Basin Using SWAT Model

The Blue Nile Basin is the main source of water for Egypt and Sudan. Most of the population in the basin depend on the water in their incomes and livelihood aspects. In the recent years, the water resources in the basin are experiencing many challenges due to climate and land use changes impacts, poor land management, and population growth. Consequently, the study of the water balance has become an urgent issue throughout the basin, especially associated with climate and land use changes as well as impacts on natural and human systems. This study Is conducted to evaluate the water resources in the Blue Nile basin using water balance technique. To achieve this objective, the water balance has been established and analyzed using the semi-distributed hydrological model, via the Soil and Water Assessment Tool (SWAT). The Climate Forecast System Reanalysis (CFSR) and Reanalysis from the Research Unit East Anglia (CRU TS 3.1) datasets were used. The model was set up using ArcSWAT software; calibrated and the validated utilizing observed streamflow data. The Sequential Uncertainty Fitting version 2 (SUFI -2) which is embodied in SWAT -CUP software was used to calculate the Nash and Sutcliffe (NSE) and the coefficient of determination (R2) as likelihood measures. The results showed that the two models established, were captured the dynamic of flow sequence very well. However, in terms of magnitudes the results indicated that the obtained flow magnitude by using the CRU dataset, 49.71 BCM, with the percent bias of 6% and the CFSR dataset, 68.63 BCM with the percent bias of 47%. The comparison between two datasets revealed that the CRU dataset with model goodness -of-fit measures of 0.66, 1.18, and 0.88 for p -factor, r-factor, and NSE, respectively, performed relatively better than the CFSR dataset with model performance measures of for p -factor, r-factor, NSE, respectively over UBNRB.