July 23 (Reuters) – China’s Three Gorges dam, the world’s largest hydropower project that was built partly to tame flooding, cannot be counted on to hold back all surges that might hit the Yangtze River, state media reported on Friday.
The dam’s own safety would be at risk if floodwaters rushed through at more than 122,000 cubic metres per second, the official China Daily quoted Zhao Yunfa, deputy director of the Three Gorges Corporation’s cascade dispatch centre, as saying.
“The dam’s flood-control capacity is not unlimited,” he said.
Waters near that volume are unlikely to test the dam often. Torrential rains across China brought a peak of 70,000 cubic metres per second flowing into the reservoir earlier this week.
During devastating floods that killed over 4,000 people in 1998, before the dam was completed, the surge was lower.
At least 701 people have died since the start of the year as a result of torrential rains which have swept large parts of southern and central China, and another 347 are missing, the government said on Wednesday.
Future floods could possibly be worse, with climate change raising that possibility. Melting glaciers and more rain in the southwest could both contribute to unusually high water levels.
China’s media have started fretting about whether the Three Gorges project will live up to one of its main long-term objectives. Officials have been toning down claims of the dam’s flood-taming abilities, the China Daily reported.
A report released in June 2003 claimed the dam could control the worst flood in 10,000 years. Four years later that claim was down to the worst flood in 1,000 years, and in 2008 it was trimmed again to the worst in 100 years, the paper said.
Enormously expensive and disruptive, the dam has cost over 254 billion yuan ($37.47 billion) and forced the relocation of 1.3 million people to make way for the reservoir. Towns, fields and historical and archaeological sites have been submerged.
Officials said the dam is opening up China’s interior to economic development, providing clean, cheap energy, and will end centuries of deadly flooding along the lower reaches of the Yangtze river.
Environmentalists have warned for years that the reservoir could turn into a cesspool of raw sewage and industrial chemicals backing onto Chongqing, and feared that silt trapped behind the dam could cause erosion downstream.
China has made scant progress on schemes drawn up nearly a decade ago to limit pollution in and around the reservoir. ($1=6.779 Yuan) (Reporting by Emma Graham-Harrison; Editing by Ben Blanchard)