The Grand Ethiopian Renaissance Dam (GERD) on the Blue Nile River has drawn significant regional and global attention for its unique location, enormous capacity and expected impacts. However, a unified policy for initially filling the reservoir has not been established among the riparian countries – a major omission at this stage. Ethiopia has incentive to fill the reservoir rapidly, optimising hydropower generation, while downstream countries prefer a modest filling rate to limit possible impacts on dependent lives and livelihoods. Future streamflow variability into the GERD reservoir, however, may significantly impact hydropower production and downstream releases under various filling policies. This work spans projecting hydroclimate variability to filling the GERD through wavelet analysis and evaluation of various filling policies (absolute, threshold and percentage-based).

This chapter is constructive on two fronts. First, both interannual and low-frequency hydroclimatic variability are accounted for in streamflow projections across the filling stage; and second, numerous filling policies are considered to provide a range of possible alternatives for negotiation between upstream and downstream countries. An introduction, hydroclimate variability projection, filling policy specifics and implications and a discussion are provided.