The Nile and its tributaries are the most important source of water for 400 million people in eleven riparian countries. The largest tributary, accounting for about 60 percent of the total runoff and 75 percent of the sediment, is the Blue Nile in Ethiopia and Sudan. How much water will the Blue Nile bring to these regions in the future? What can be done to better manage irrigated agriculture and water reservoirs, in particular the new Grand Ethiopian Renaissance Dam? German, Sudanese and Ethiopian participants in the joint project SPS-Blue Nile aim to develop a meteorological-hyd- rological forecasting system for the transboundary water management of the Blue Nile. The goal is to create a “seam- less” approach with interconnected forecast horizons ranging from days to several months. This will enable a compre- hensive, transboundary assessment and derivation of recommended actions within the water-food-energy nexus.