Africa's largest hydropower facility is currently under construction on the main stem of the Blue Nile River in Ethiopia. The Grand Ethiopian Renaissance Dam (GERD) is poised to facilitate regional development with a 63 billion cubic meter reservoir and 6,000 MW of power generating capacity. To date, however, no reservoir filling rate policy has been established. This policy will have clear implications on the GERD's ability to generate hydropower in the near-term and coincidentally impact people and livelihoods in Sudan and Egypt through reduced streamflow availability. Implications of climate variability and emerging climate change within Ethiopia cast further uncertainty on potential filling policies and system operations. To address this challenge, numerous filling policies are evaluated through a climate-sensitivity approach to estimate impacts on reservoir filling time, hydropower production, and downstream flows. This provides viable and timely points of comparison for regional water managers and politicians negotiating system operations in the midst of ongoing project construction.