Would Africa's largest hydropower dam have profound environmental impacts?

Abstract

In the face of rapid growth in the global demands for water, energy, and food, building large dams is expected to continue. Due to its potential opportunities and risks for the people of the Eastern Nile Basin, the Grand Ethiopian Renaissance Dam (GERD) on the Nile Riverhas commanded regional and international attention. Once completed, it will rank the largest hydropower dam in Africa and among the largest worldwide. Discourse among scientists and negotiators from Ethiopia, Sudan, and Egypt on the design, initial filling, and long-term operation of the GERD is ongoing since the construction started in 2011, but no agreement has yet been reached. The discourse has hitherto focused on the impacts on hydropower production, water availability, and irrigated agriculture, with little attention to the dam's potential environmental impacts. Here, we communicate our viewpoint on this gap, drawingon knowledgefrom other dams around the world and some GERDcharacteristics. The hydrological alterations associated with the GERD could adversely impact fish, aquatic plants, and biodiversityin the downstream due to possiblechanges in water temperature, salinity, and oxygen content. The GERD's expected flooded area, location at low latitude in the tropics, and the deep turbine intakes could intensify greenhouse gas emissions,whereas the dam'shigh reservoir depth would abate the emissions. The dam's electricity could also reduceregionalgreenhouse gas emissions if combined withcleaner intermittent solar and windenergy sources. With a maximum reservoir area of 1904 km2, surface evaporation and consequently local extreme precipitation and humidity could increase. Theaforementioned impacts could have transboundary ecological, agricultural, and health implications and, therefore, should be taken intoconsideration alongside the benefits of the dam.