Regional climate modeling of the Nile Basin

It is increasingly recognized that appropriate water resources planning and management at a river basin level is viable only by considering the complete water cycle in the basin, i.e., including both the land surface (hydrological) and the atmospheric processes. In many river basins, steady climatic conditions are no longer considered a valid assumption for sustainable water resources management. Therefore, despite its significant computational effort water resources studies at river basin level are increasingly linked to regional climate studies. Examples are studies on impact of climate change/variability on water resources or the studies of land use change and their impacts on regional climate and water resources (see a review in Watson et al., 2001 ). Similarly, it is appreciated that adequate representation of the land surface in climate models is crucial for accurate modeling results ( Kite, 1998 ; Koster et al., 2002 ).