Cooperative operation of the Grand Ethiopian Renaissance Dam reduces Nile riverine floods

Abstract

The construction of the Grand Ethiopian Renaissance Dam (GERD) on the Nile River has triggered much debate between Ethiopia, Sudan, and Egypt on the dam's effects.Once completed, the GERD will be Africa's largest hydropower plant. This study analyzes the implications of cooperative long-term operation of the GERD for Nile riverine flooding downstream of the dam. A daily river system model of the Eastern Nile is developed and used to examine how cooperative long-term operation of the GERD would affect the occurrence of three flood alarm levels (alert, critical, and flooding) in Sudan downstream of the dam. A reconnaissance-level flood inundation model is developed for the Nile within Khartoum State (Sudan's capital) to assess the GERD's impacts on the flood extent in the state based on simulated flows from the river system model. Assuming the GERD is operated to achieve a 90% power reliability and active upstream-downstream data sharing between Ethiopia and Sudan on the dam's daily outflows, results show that the GERD would reduce the occurrence of the three alarm levels. Based on 34 simulated river flow sequences, the proportion of years with at least one flooding alarm day at Khartoum Gage declined from 37% without the GERD to 11% with the GERD. Seasonal coordination and planning between Ethiopia and Sudan are necessary to mitigate the remaining riverine flood hazard.Although cooperative long-term operation of the GERD could play a positive role in reducing the riverine flood hazard in Sudan, the associated river flow alterations would adversely impact recession agriculture and the environment.

Cooperative adaptive management of the Nile River with climate and socio-economic uncertainties

“…This interim drought mitigation measure is activated only if the GERD storage is above a threshold termed the drought outflow storage threshold. The operations of the seasonal storage dams downstream of the GERD follow their historical rules during the GERD's filling phase, whereas their reservoirs are kept as high as possible during the long-term operation phase, similar to assumptions made by previous studies, assuming data sharing between Ethiopia and Sudan 7, [14][15][16] .…”

“…The dam is expected to result in a range of opportunities and risks to Sudan and Egypt. Subject to coordination and data sharing, hydropower generation, irrigation water supply reliability and flood control in Sudan could improve because of the dam [13][14][15][16] . Still, the dam will probably produce adverse environmental impacts and losses to recession agriculture in Sudan 17 .…”

Policy conflict around the Grand Ethiopian Renaissance Dam

“…The first recommendation is for Ethiopia to ensure it addresses information loopholes in the access to reliable hydrologic statistics (data and forecasts) of the GERD. Ethiopia has insufficiently disclosed the detailed plan for filling the hydropower reservoir and how much water would be released through the GERD's gates (Basheer, 2021; Wheeler et al, 2020). In the absence of a legally binding agreement on the filling and operation of the GERD, a lack of official hydrology statistics and the Ethiopian government's reluctance to share the information exacerbates perceived threats to Egypt and Sudan because of the likelihood of diminishing the Nile River's downstream water resources (Bermudez et al, 2021; Heggy et al, 2021; Nile Basin River Advisory System, 2023).…”

Collaborative management of the Grand Ethiopian Renaissance Dam increases economic benefits and resilience

“…However, the initial filling and long-term operation of the GERD reservoir are expected to significantly alter the pattern of flow of the Blue Nile downstream of the dam, imposing a range of opportunities and risks to Sudan and Egypt [24][25][26] . Sudan is expected to benefit from the GERD in terms of improved irrigation water supply reliability, hydropower generation, and riverine flood control provided there is essential daily coordination and data sharing with Ethiopia 24,27 , but adverse environmental impacts and a loss of recession agriculture are also anticipated 28 .…”

“…Previous studies have investigated the impacts of GERD filling and long-term operation on Ethiopia, Sudan, and Egypt [24][25][26][27][36][37][38][39][40] . However, these studies used simple representations of the linkages between the river system and the Eastern Nile economies.…”