Seven years ago, the massive Three Gorges Dam was hailed by China's official media as being able “to withstand a once in 10,000 year flood.”

But as China's south was ravaged by floods this week — the worst in a decade — the multi-billion dollar dam's actual capacity to deliver has become a subject of much debate for the media and environmental groups here.

More than 273 people have died in this month's flooding, which has also destroyed 330,000 homes and dislocated tens of thousands of residents. This is the worst flooding in China since the devastating 1998 floods, which claimed 4,150 lives.

On Friday, the water-level of the Three Gorges Dam reached its peak for this year, to 13.86 metres above its reservoir's water-releasing level. The water-level has now risen to 158.86 metres, only 16.17 metres short of its maximum capacity.

The dam's construction, which as of 2008 had cost $26.5 billion and displaced more than one million people, has been justified by the government as an essential solution to the Yangtze river's recurring flooding problems.

The dam faced its toughest test yet since it opened in 2008 on Friday, with peak flows forecast to touch 70,000 cubic metres a second.

With the Yangtze's upper reaches continuing to swell, huge waves of water were released from the dam at 40,000 cubic metres per second, prompting concerns that opening the sluice-gates would cause further damage downstream.

This month's flooding has stirred debate about the dam's flood-control capabilities. One article that has attracted much attention online, and even found mention in the official media, has accused the government of initially overstating the dam's capabilities in selling the project to the public, and then gradually toning down expectations.

The article pointed to a series of headlines from the official media over the past decade. One headline, from June 2003, claimed the dam could handle “the worst flood in 10,000 years.” A second, from 2007, said it could handle “the worst flood in 1,000 years”. Two years ago, that figure was down to 100 years.

This week, officials went a step further, telling the public to “not lay all hopes” on the dam. Zhao Yunfa, deputy director of the China Three Gorges Corporation's cascade dispatch centre, told the official China Daily newspaper that the dam's flood-control capacity was limited, and designed to only withstand floods with flows of 83,700 cubic metres per second.

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