Changes in Water Resources Systems: Methodologies to Maintain Water Security and Ensure Integrated Management (Proceedings of Symposium HS3006 at IUGG2007, Perugia, July 2007).  IAHS Publ. 315, 2007, 284-291

 

Blue Nile flow sensitivity to projected climatic change until 2100

 

RIZWAN NAWAZ1 & TIMOTHY BELLERBY2

1 Earth and Biosphere Institute, University of Leeds, Leeds LS2 9JT, UK

n.r.nawaz@leeds.ac.uk

2 Department of Geography, University of Hull, Hull HU6 7RX, UK

 

Abstract The sensitivity of Blue Nile flows (which contribute the bulk of the Nile water) to changes in future rainfall during the June–September rainy season based on output from three General Circulation Models (GCMs) was determined up until 2100. The study attempted to quantify uncertainties aris­ing from: (a) use of different GCMs; (b) different greenhouse gas emissions scenarios; and (c) downscaling coarse-scale GCM output to a finer-scale required for hydrological modelling. A multidimensional stochastic rainfall generator was developed to produce high-resolution gridded rainfall data required by the distributed hydrological model (Nile Forecast System). The assessment also incorporated future evapotranspiration changes over the basin, although in a more simplistic way. Two of the GCMs (Canadian Climate Centre’s CGCM2 and UK Hadley Centre’s HadCM3) led to reductions in future mean flow and Q5 (daily flow exceeded 5% of the time) during the rainy season, whilst use of the third GCM (Max Plank Institute’s ECHAM4) led to general increases in future mean flow and Q5. Changes were more pronounced by the 2050s and 2080s.

 

Key words  Blue Nile; climate change; downscaling; stochastic; uncertainty