Floods test limits of Three Gorges Dam

Floods test limits of Three Gorges Dam

Chinese reservoir close to overflowing after weeks of heavy rain

An aerial photo taken on Wednesday shows a flooded area in Chongqing in southwestern China. Floods have washed away roads and forced tens of thousands from their homes, with authorities warning that the giant Three Gorges Dam is facing the largest flood peak in its history. (AFP Photo)
An aerial photo taken on Wednesday shows a flooded area in Chongqing in southwestern China. Floods have washed away roads and forced tens of thousands from their homes, with authorities warning that the giant Three Gorges Dam is facing the largest flood peak in its history. (AFP Photo)

Water levels at China’s giant Three Gorges Dam on the Yangtze river are inching closer to their maximum after torrential rains raised inflows to a record high.

With 75,000 cubic metres per second of water flowing in from the Yangtze river on Thursday, the reservoir’s depth reached 165.6 metres by Friday morning, up more than two metres overnight and almost 20 metres above the official warning level.

The maximum designed depth of China’s largest reservoir is 175 metres.

The flow of water into the reservoir has shattered the previous record of 61,000 cubic metres per second set just last month, according to a statement from the Ministry of Water Resources.

Authorities raised the discharge volume to a record 48,800 cubic metres per second on Thursday to try to lower water levels, and they might have to increase it again to avoid the possibility of a dangerous overflow.

Since the floods began in June, officials have repeatedly offered reassurances that the dam could withstand what has been called once-in-a-century flooding. Some reports in state media have gone further, claiming that the dam had almost certainly prevented even worse flooding in major cities downstream, including Wuhan, where the Covid-19 pandemic began.

On Friday, officials announced that the flow into the Three Gorges dam had eased somewhat, though they remained on alert.

“They will do everything they can to prevent the dam from overtopping,” said Desiree Tullos, a professor at Oregon State University who studies the Three Gorges project.

“An overtopping dam is a worst-case scenario because it produces significant damage … and can lead to the entire thing collapsing.”

Rainfall in the Yangtze basin has been well over double the seasonal average this year. The floods had caused nearly 180 billion yuan (US$26 billion) in economic damages by last week, and 63 million people have been affected.

The Three Gorges project, completed in 2012, was designed not only to generate power but also to tame the fierce Yangtze, the cause of many devastating floods throughout China’s history.

China’s giant hydroelectric dams have stored more than 100 billion cubic metres of floodwater this year, and shielded 18.5 million residents from evacuation, according to government figures. The Three Gorges project alone has cut downstream floodwaters by 34%, officials said.

But opponents say the flood control capability of the Three Gorges Dam is limited, and it could even make the problem worse in the long term.


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