The results of the study, which were announced on 8 April in the scientific journal Nature Energy, show that integration of a complementary hydro-solar-wind production system would be able to deliver fivefold benefits across the three countries: decarbonizing power generation in the EAPP; ensuring compliance with Sudan’s environmental flow needs; optimizing GERD infrastructure use; harmonizing the annual refilling schedules ofthe GERD and Egypt’s High Aswan Dam, and supporting diversification of Ethiopia’s power generation mix for domestic use and exports. “Our results call for integrated hydro-solar-wind planning to be taken up in the GERD negotiations,” the lead author of the study, Sebastian Sterl of Vrije Universiteit Brussel, told H&D.
The ongoing construction of the GERD, on the Blue Nile, near the border between Ethiopia and Sudan, has been the subject of long-running and increasingly politicized negotiations between the three countries. With an installed capacity of more than 5 GW, the project will substantially increase Ethiopia’s electricity generation, electrification and industrialization, but Egypt and Sudan fear it will have impacts downstream. Egypt, in particular, fears losing its control over the Nile flow, with adverse effects on agriculture.
Most of the discussions are focused on the first filling of GERD’s reservoir (74 x 109 m3 or 1.6 years of average Blue Nile discharge), with Egypt is contesting Ethiopia’s proposed timeframe of 4 to 7 years. But as researchers stress, while any compromise on filling time will allay concerns for a limited time, greater attention needs to be paid to the long-term operational strategy of GERD, as the downstream impacts of post-filling operation could last more than a century. It is important fort long-term strategies with benefits for all be identified for operation of the scheme. The reservoir storage capacity would allow near-full control of the Blue Nile’s seasonal flow, providing year-round generation. Given that Ethiopian electricity demand is fairly unseasonal, Ethiopia’s preferred objective for long-term operation of the GERD would suggest near-constant outflow. This would alter the river’s natural discharge seasonality, with mixed results for Sudan and potentially negative consequences for Egypt. For Sudan it could mitigate dry periods, improve flood control, reduce sedimentation and benefit its own hydropower and irrigation. For Egypt, which controls the flow of the Nile to meet its own water needs through Lake Nasser and the High Aswan Dam (HAD), the damming of the Blue Nile, which contributes up to 60 per cent of overall Nile flow, could negatively affect Lake Nasser’s refilling by holding water back in dry years. In addition, while GERD would guarantee a minimum dry season flow for Sudan, this would possibly increase water extraction for irrigation in Sudan, potentially reducing the flow reaching Egypt.
A controlled seasonality of outflow from GERD would be preferable for both Egypt and Sudan, but would undermine the primary intention of its development by Ethiopia, according to the study. However, given that solar and wind have opposite seasonal profiles to the Blue Nile flow, the study found that if GERD were instead operated to back up solar and wind throughout the year, both hourly and seasonally, this would not affect GERD’s average annual output, and would provide less hydropower during the dry seasons, but more during the wet season. The water discharged from the dam would then have a seasonality resembling the natural river flow, with a clear peak in the wet season. “Ethiopia would have all the expected benefits of a large dam, but for Sudan and Egypt it would be as if Ethiopia had only built a dam with a relatively small reservoir,” said Sterl.
According to the study, the entire region would stand to benefit from integrated hydro-solar-wind planning. “Ethiopia could theoretically proceed alone, using GERD to back up its own solar and wind power,” said Sterl. “But it would work much better if Sudan were to join in; it has better solar and wind resources than Ethiopia, allowing for greater hydro-solar-wind synergies and reducing the overall costs of renewable power generation. Ethiopia has substantial solar and wind resources too, as do Djibouti, South Sudan and other eastern African countries. Regional cooperation in an Eastern African Power Pool could be key, with benefits for all,” concluded Sterl.