A hydro dam currently under construction in Ethiopa is set to be the largest hydropower plant in Africa, but could be heading towards controversy for international agreements on water sharing.

New Research from a University of Manchester led consortium points out that some negotiated strategies for filling Ethiopia’s new Grand Ethiopian Renaissance Dam (GERD) dam could be infeasible in critical river flow conditions due to the limited ability of the dam to release water at low water levels.

The University of Manchester led team argues that the possible inability of the dam to follow an eventual international agreement could create controversy and complicate future efforts to share water and electricity in East Africa.

The GERD dam, a large hydropower dam with an installed capacity of 5,150 Mega Watts, is under construction on the Blue Nile in Ethiopia. Construction began nearly a decade ago and when completed, the GERD will be the largest hydropower plant in Africa and the tenth largest globally.

The main purpose of the dam is domestic and regional electrification and it is expected to improve electricity access in East Africa through existing and planned power interconnections. But realising benefits will require filling the associated reservoir by retaining water that would have otherwise flowed downstream.

The volume of the GERD reservoir is around 1.5 times the average annual flow of the Blue Nile. This means filling it up in one go is out of the question, as that would prevent any water from flowing downstream and deplete most of the Nile river.

Debate on the GERD’s filling have been ongoing since the dam was announced. Negotiations between Ethiopia, Sudan, and Egypt on the initial reservoir filling and long-term operation of the GERD took place in Washington in November 2019 to February 2020.

The Manchester team state that the consideration of engineering constraints due to the dam design and construction should inform negotiations over initial reservoir filling to help prevent unnecessary political tension later on.