Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 13 5 2009 10.5194/hess-13-551-2009 http://www.hydrol-earth-syst-sci.net/13/551/2009/ http://www.hydrol-earth-syst-sci.net/13/551/2009/hess-13-551-2009.html http://www.hydrol-earth-syst-sci.net/13/551/2009/hess-13-551-2009.pdf 551 565 2009-05-06 Impacts of climate change on Blue Nile flows using bias-corrected GCM scenarios M. E. Elshamy meame_69@yahoo.com I. A. Seierstad A. Sorteberg Nile Forecast Center, Ministry of Water Resources and Irrigation, Egypt Nile Basin Research Programme, University of Bergen, Norway Bjerknes Center for Climate Research, University of Bergen, Norway Geophysical Institute, University of Bergen, Norway This study analyses the output of 17 general circulation models (GCMs) included in the 4th IPCC assessment report. Downscaled precipitation and potential (reference crop) evapotranspiration (PET) scenarios for the 2081–2098 period were constructed for the upper Blue Nile basin. These were used to drive a fine-scale hydrological model of the Nile Basin to assess their impacts on the flows of the upper Blue Nile at Diem, which accounts for about 60% of the mean annual discharge of the Nile at Dongola. There is no consensus among the GCMs on the direction of precipitation change. Changes in total annual precipitation range between −15% to +14% but more models report reductions (10) than those reporting increases (7). Several models (6) report small changes within 5%. The ensemble mean of all models shows almost no change in the annual total rainfall. All models predict the temperature to increase between 2°C and 5°C and consequently PET to increase by 2–14%. Changes to the water balance are assessed using the Budyko framework. The basin is shown to belong to a moisture constrained regime. 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