Giant Three Gorges project on the mighty Yangtze River ready for its biggest test, as the worst conditions may be yet to come

While downpours continue to threaten Chinese towns and cities, the Three Gorges Dam, widely seen as the solution to frequent flooding along the Yangtze River, is braced for potentially bigger surges this year.

Lu Chun, chairman of China Three Gorges Corp, which operates the dam, says the company is preparing for flooding along the Yangtze that could be exacerbated by freak weather conditions.

Floods have already killed more than 200 people and affected about 60 million in China this year, with the lower reaches of the Yangtze among the hardest hit. Yet the worst could still be to come, according to Lu, who predicted an "extremely high possibility" of basin-wide flooding when he met with officials from the Ministry of Water Resources.

Those in charge of the giant dam believe the project is ready to pass its biggest test since it was completed in 2009, which could occur in the coming weeks, although they have also attempted to manage public expectations about the dam's role in flood control.

Wang Yuhua, deputy chief engineer with the corporation's cascade dispatch and communication center, says the dam is "fully capable" of controlling floods in the middle and lower reaches of the Yangtze, although he added "within its design standards".

At 2,309 meters long and 185 meters high, the world's most powerful dam reduces the risk of flooding by trapping large amounts of water from the upper reaches of the river and reducing the flow downstream.

While the dam places flood control above its other functions, including power generation, executives say it is intended mainly to ease flooding of the Jingjiang River, a winding branch of the Yangtze in Hubei province that is close to important industrial and agricultural centers with dense populations.

In the event of the worst flooding in 100 years, with a water flow of 83,700 cubic meters a second, for example, the dam would guard the Jingjiang River by cutting the flow to 56,700 cu m a second. In the event of a stronger flood, the dam would need to work with other local flood-diversion measures to reduce the flow to 80,000 cu m a second to protect dams and cities further down the river.

Wang says the most fierce floods this year were on July 1, when water gushed into the dam at a rate of 50,000 cu m a second, which it then pumped out at 31,000 cu m a second.

On July 15, as heavy rain battered the Yangtze, the inflow to the reservoir was recorded at 32,000 cu m a second, with the outflow 18,900 cu m a second.

Wang shrugged off public concern about the dam's ability to cope with severe flooding like that seen in 1998, the worst in recent memory, which left about 1,800 people dead and affected more than 100 million.

"If the dam had been built earlier, the 1998 disaster could have been averted," says Wang, adding that the dam had handled bigger floods in 2010 and 2012, with peak flows of 70,000 and 71,200 cu m a second respectively. Statistics show the peak during the 1998 floods was 66,800 cu m a second.

Flood control officials on the front lines agree the dam is the main reason the situation along the Yangtze has remained under control this year.

Chen Min, director of the Yangtze River Flood Control and Drought Relief Headquarters, said that on July 8, eight hours after the dam reduced outflows, flood levels ceased to rise near Jianli, a key monitoring post on the Jinjiang River. The pressure also began to ease further downstream at Chenglingji in Hunan.

"The Three Gorges Dam has played the part of an unsung hero," Chen says. "It quietly keeps the water flowing at levels that people on the lower reaches can handle."

Huang Xianlong, an official with the Office of State Flood Control and Drought Relief Headquarters, has dismissed media reports that claimed the dam is useless and counterproductive. "In fact, the more critical the situation, the more obvious and positive the dam exerts its role," he says.

Contact the writers through lvchang@chinadaily.com.cn