The waters behind the Three Gorges Dam, the world's largest hydro-electric project, are expected to reach their maximum level by the end of the month, according to the China Three Gorges Corporation. The dam began backing up water in 2003.

Two previous attempts to reach the maximum depth of 175 meters, in 2008 and 2009, failed. The first happened when the level reached just over 172 meters and caused geological problems along the upper reaches of the Yangtze River. The second happened when the water reached a depth of just over 171 meters and people downstream found themselves in urgent need of water supplies.

This third attempt to reach the level the dam was designed for began on Sept 10, at a level of 160.2 meters. The trial has gone smoothly so far, with the level reaching a record high of just over 174 meters by 3:00 PM on Wednesday, according to China Three Gorges Corporation's monitoring system.

The flow, upstream, is expected to be stable over the next few days, with the outflow also steady at 7,000 cubic meters per second.

Judging from the current situation, it's likely that water levels will reach 175 meters by the end of the month, according to the Yangtze River Flood Control and Drought Relief Headquarters.

If the water reaches a depth of 175 meters, said Cao Guangjing, board chairman of the China Three Gorges Corporation, it means the Three Gorges project's main goals of flood prevention, power generation and shipping will be conforming to design standards.

"It's only at a level of 175 meters that all 26 of the generating units, each with a 700,000-kilowatt capacity, will be fully operating," Cao was quoted by the Xinhua News Agency as saying.

If that is the case, the dam will have an annual output of 84.7 billion kilowatt hours of power, 10 billion kWh more than what would be generated at a level of 156 meters.

At the higher level, navigation on the upper reaches of the river is better, Cao said.

Nonetheless, experts worry about the possible geological impact of the higher water levels. For example, there has been a succession of landslides, erosion activity and sedimentation in the reservoir area around Hubei's Zigui and Badong. At least half of the land in the reservoir area is experiencing some erosion, depositing about 40 million tons of sediment into the reservoir annually, Chongqing Daily has reported.

China has set aside 12 billion yuan (US$1.8 billion) in funds to deal with geological problems in the Three Gorges area and has established a geological disaster warning system, since 2001, according to official figures.

"Just a few days ago, the river bank in the town of Guojiaba collapsed in several places," said Tang Zuoyou, of the Yichang land and resources bureau, on Tuesday.

Tang said the local government has contingency plans to deal with such problems. "The reservoir's edges are very fragile, and we should pay particular attention to them."

The Three Gorges Corporation has said they will monitor the geographic conditions in the reservoir area more closely as the water rises to make sure that everything runs smoothly.

(China Daily October 21, 2010)