Located downstream from the headwaters of the Abay, or Blue Nile, River in the Ethiopian Highlands, the Grand Ethiopian Renaissance Dam (GERD) is set to become Africa’s largest hydroelectric power plant. Still under construction, it is eventually expected to be able to generate more than 6,000 megawatts of electricity, which will provide power for about half of Ethiopia’s population and also allow the country to export electricity to neighboring nations. Ethiopia has argued it needs the dam’s electricity to modernize and grow.
The dam would affect the flow of the Nile to downstream residents in Sudan and Egypt and has become a major point of contention over water rights along the river. Scientists and engineers have also voiced concerns over the dam’s structural integrity because of its location in a mountainous terrain in an active tectonic region.
As satellite imagery shows the dam’s reservoir beginning to fill, Ethiopia, Sudan, and Egypt are negotiating to reach a political consensus on safe operational management to ensure health and sustainability in the region.
Damming Water in an Unstable Terrane?
The dam will ultimately create a reservoir with a capacity of 74 billion cubic meters of water. Since construction began in 2011, the project has been contentious among Ethiopia, Sudan, and Egypt, as 74 billion cubic meters of water is coincidentally what Sudan and Egypt negotiated in the 1959 Nile Waters Agreement. (That agreement’s allotment includes the flows of both the Blue Nile and the White Nile, which meet at a confluence near Khartoum, Sudan. The northward flow of the White Nile from Lake Victoria, a much lower volume than the Blue Nile, remains largely unimpeded.)
Some engineers have cited research suggesting that the dam is vulnerable to environmental hazards that may cause it to collapse. Seismicity is not the least of these concerns, as the project abuts one of the largest rift zones on Earth: the Great Rift Valley.
“Ethiopia is the most seismically active African country,” said Abbas Sharaky, a professor of geology at Cairo University. In the past 5 years, Ethiopia has had at least five earthquakes measuring from M4.0 to M5.3. “The dam itself and its reservoir are located on a fault.…[Part of the dam] is arched so that the concave side faces the lake, making it weak and vulnerable to collapse.”
Roger Bilham, a professor of geological sciences at the University of Colorado Boulder, mitigates some of these concerns. He said that the dam lies about 500 kilometers to the west of the Afar Triple Junction, a divergent plate boundary where the Nubian, Somali, and Arabian tectonic plates interact. Major earthquakes are rare beyond a distance of about 200 kilometers, Bilham said.
“Earthquakes are frequent along [plate] boundaries, but they tend to be rather small (less than M5) because the Earth’s crust is warmer and thinner than elsewhere and is therefore unable to sustain large damaging earthquakes,” Bilham added.
However, Hesham El-Askary explained, because the dam’s location is tectonically active, an excessive amount of pressure can cause the faults to slip. El-Askary is a professor of remote sensing and Earth system sciences at Chapman University in Orange, Calif. He is currently on leave with the Department of Environmental Sciences at Alexandria University, Egypt, where he is conducting research on natural hazards and the geology of the Grand Ethiopian Renaissance Dam.
“If you are constructing a huge water body like the reservoir of GERD, this causes a massive amount of pressure on the Earth’s crust,” leading to fault slippage and earthquakes, El-Askary said.
Bilham tentatively agreed. “I consider it very probable that earthquakes will indeed be induced by the GERD project, as for example occurred when the Kariba and Aswan dams were first filled.”
Representatives from the Grand Ethiopian Renaissance Dam and the Italian company Pietrangeli, which is implementing the project, did not respond to multiple calls for comment.
Other Risks
Landslides and flooding present other risks to the dam, according to published reports. The source of the Blue Nile is Lake Tana, which sits 1,788 meters above sea level in the Ethiopian Highlands. The river moves across steep and sometimes unstable slopes as it approaches the dam. Sharaky pointed out that “water falls heavily during the rainy season in July, August, and September, and the average of daily water flow is over 600 million cubic meters.”
Flash floods or unexpected water inflows from heavy rainfall—expected to increase with climate change—could raise water to levels the dam might not be able to handle, and trapped silt may make it even more vulnerable to collapse or spillover, researchers have noted. Over the past 40 years, existing dams in Sudan and Ethiopia have lost around half their capacity to siltation.
More Water, More Words
Concerns about the structural integrity of the Grand Ethiopian Renaissance Dam have become more urgent this summer as recent satellite imagery showed the reservoir behind the dam beginning to swell.
The Ethiopian government denied purposely filling the reservoir, instead attributing rising water to heavy rains in the region. Earlier, Ethiopia’s water minister Seleshi Bekele had attributed rising water levels to the construction process of the dam, although not confirming whether the process involved testing the dam or actually storing water in the reservoir.
“The [Ethiopian] government has not stated explicitly whether the water backing up behind the dam is due to the remaining outlets being closed, or whether it is simply water accumulating behind the almost complete structure during the rainy season,” William Davison, an analyst with International Crisis Group, told the South China Morning Post.
In June and July, representatives from Egypt, Sudan, and Ethiopia engaged in two rounds of full negotiations surrounding the dam’s operation, one chaired by the United Nations and the other sponsored by the African Union. The African Union talks included a “minisummit” video conference hosted by African Union chair and South African president Cyril Ramaphosa and attended by leaders from the three countries, as well as officials from the Democratic Republic of the Congo, Kenya, and Mali.
At the minisummit, leaders agreed to resume full talks at an unspecified later date, focused on forming a legally binding agreement on the filling and operation of the dam.
—Mohammed El-Said (@MOHAMMED2SAID), Science Writer
6 August 2020: This article has been updated to clarify the expertise of Hesham El-Askary.