One of Africa’s Biggest Dams Is Falling Apart
The new year has not been kind to the hydroelectric-dam industry. On January 11th, the New York Times reported that Mosul Dam, the largest such structure in Iraq, urgently requires maintenance to prevent its collapse, a disaster that could drown as many as five hundred thousand people downstream and leave a million homeless. Four days earlier, the energy minister of Zambia declared that Kariba Dam, which straddles the border between his country and Zimbabwe, holding back the world’s largest reservoir, was in “dire” condition. An unprecedented drought threatens to shut down the dam’s power production, which supplies nearly half the nation’s electricity.
The news comes as more and more of the biggest hydroelectric-dam projects around the world are being cancelled or postponed. In 2014, researchers at Oxford University reviewed the financial performance of two hundred and forty-five dams and concluded that the “construction costs of large dams are too high to yield a positive return.” Other forms of energy generation—wind, solar, and miniature hydropower units that can be installed inside irrigation canals—are becoming competitive, and they cause far less social and environmental damage. And dams are particularly ill-suited to climate change, which simultaneously requires that they be larger (to accommodate the anticipated floods) and smaller (to be cost-effective during the anticipated droughts).
Mosul Dam’s predicament is partly a result of the ongoing war; many maintenance workers have not returned there since August of 2014, when ISISfighters briefly took control. (Iraqi and Kurdish forces soon regained it.) But the main issue is that, like many such dams, the project shouldn’t exist in the first place. Opened in 1986, it was built on unstable gypsum bedrock, requiring grout to be constantly injected into the foundation to prevent the dam’s collapse. That work has ceased. In 2006, long before ISIS began making headlines, the U.S. Army Corps of Engineers called Mosul Dam “the most dangerous dam in the world.”
Kariba’s difficulties are more complicated. It has been nearly incapacitated by ongoing drought, which has lowered the reservoir’s volume to twelve per cent of its usual capacity. But if the reservoir is refilled, the dam faces the possibility of collapse. It was built in the late nineteen-fifties, and in the years since water flowing through the dam’s six floodgates has carved a three-hundred-foot-deep pit, or plunge pool, at its base. The plunge pool extends to within a hundred and thirty feet of the dam’s foundation; if it reaches the foundation, the dam will collapse. That seems hard to imagine now, with the reservoir at a record-low level. But the Zambezi River Basin, on which the dam sits, is the most susceptible of Africa’s thirteen basins to exceptional droughts and floods, and climate change is intensifying both.
Kariba’s collapse, like Mosul’s, would constitute an epochal event in the history of energy development—the dam industry’s Chernobyl. The ensuing torrent would be four times bigger than the Zambezi’s biggest recorded flood, in 1958, and would release enough water to knock over another major dam three hundred miles downstream, in Mozambique. At least three million people live in the flood’s path; most would die or lose their crops or possessions. About forty per cent of the electricity-generating capacity of twelve southern African nations would be eliminated.