(July 20, 2010) Three Gorges officials admit defeat and warn the public that the controversial dam’s reservoir cannot story its maximum capacity, writes Patricia Adams.

While Three Gorges dam officials congratulate themselves for holding back the Yangtze’s largest floodwaters since 1998, the head of the Changjiang Water Resources Commission has cautioned the public that the dam cannot store its maximum capacity at 175 metres because 28,470 people still live on the reservoir’s edge, below that level.

“In theory,” Cai Qihua, director of the Wuhan-based Changjiang Water Resources Commission told China Central TV, “the Three Gorges dam should be able to deal with a one-in-hundred year flood, but not this year because those people have not yet been moved.” So, “don’t expect the Three Gorges dam to do everything,” she cautioned.

Meanwhile, the Three Gorges Corporation’s decision to release water in preparation for the floods from upstream actually exacerbated downstream flooding caused by rainstorms that hit Hunan, Hubei and Jiangxi provinces below the dam. The dykes downstream are particularly vulnerable as many have been eroded by the fast flowing and clear water disgorged from the Three Gorges dam.

Zhao Mu-sen, Deputy Director of the Operating Management Bureau of the Three Gorges Corporation, told a reporter from the Chinese New Century Weekly that the dam operators had no choice.

Mr. Zhao also warned that given the flood-prone nature of areas downstream of the Three Gorges dam, the huge and sudden volumes that can come from upstream, and the relatively small capacity of the Three Gorges reservoir, the dam’s flood control capacity is insufficient to solve the flooding problem.

“The Three Gorges dam cannot win the battle against floods alone,” he said, “even when it is fully operational at 175 metres.” Only a system of dykes and flood diversion areas, the age-old system, “can achieve a permanent solution to the flooding problem,” Mr. Zhao added.

Observers from across China and around the world held their breath today as the speed of flows from the upper reaches of the Yangtze River topped 70,000 cubic metres per second, 20,000 cubic metres more than the flow during the 1998 floods that killed 4,150 people and the highest level since the dam was completed last year. That flow is expected to drop to 60,000 cubic metres a second by 8 a.m. July 21.

According to official Chinese news sources, 38 million people have been affected by the heavy rains, 1.3 million have been relocated, some 124,000 houses have collapsed and another 327,000 damaged, with economic losses reaching almost 20 billion yuan (US$4.4 billion).

Apart from the fact that thousands of people are still living below the high water level mark of 175 metres, the Three Gorges reservoir has never been filled to its 175 metre maximum because drought caused a shortage of water and because officials feared raising the reservoir level would trigger more potentially deadly landslides. The Three Gorges reservoir, which saturates and destabilizes the reservoir banks has been blamed for 166 landslides and caused the evacuation of thousands of residents.

Three Gorges operators now have the unenviable task of choosing who to put at risk, those upstream or those downstream, when they decide how much water to retain and how much to sluice through.

Patricia Adams, Probe International

Further Reading:

• More landslides likely as Three Gorges reservoir rises
• Fragile Three Gorges: Caijing magazine reports
• The Three Gorges reservoir has become a danger
• China’s Three Gorges Dam withstands peak flood test
• Three Gorges dam implicated in serious embankment breaches
• Three Gorges Flood Control Analysis
• Top scientists call for Three Gorges monitoring stations
• EDITORIAL: As Three Gorges ramps up, operating conflicts will intensify