27. Impact and Benefit Study of Grand Ethiopian Renaissance Dam (GERD) During Impounding and Operation Phases on Downstream Structures in the Eastern Nile

The Government of Ethiopia has undertaken the implementation of the 6,000 MW Grand Ethiopian Renaissance Dam Project (GERD) located on the Blue Nile just upstream of the Ethiopian–Sudan border. The GERD has an active storage capacity of 60,000 million m³ (million cubic meter) which is greater than the yearly average flow of 48,770 Mm³, thus acting as a multiannual regulating reservoir. The objective of this chapter is to analyze potential impacts and benefits of GERD on Eastern Nile, mainly on the High Aswan Dam (HAD) and reservoirs in Sudan. Simulations have been based on monthly flow data considering specific series of years as representative of a possible near-future scenario during GERD filling and operation. For the GERD impounding stage, average sequences of inflows are selected according to a 6-year (planned period to fill GERD reservoir) moving average on HAD yearly inflows time series. The scenarios were evaluated by comparing the current situation (HAD alone) and with GERD. More regular and constant flows will be released to downstream of GERD. At the Sudanese border, peak flows on the Blue Nile are controlled and reduced by GERD (reduction of 85 % of the maximum monthly flow) while low flows are significantly increased ( + 300 %). Evaporation losses are reduced by 12 % comparing to the current situation. Egyptian irrigation water demand is always satisfied during the simulated period.