Dams and Landslides

More landslides likely as Three Gorges reservoir rises

(November 9, 2009) The Three Gorges reservoir will face an increasing number of landslides and other geological dangers if government officials persist in raising the level of water to its maximum height, says a report by Caijing magazine. The report, citing a research paper by the Chongqing Political Consultative Conference, says the higher the reservoir, the greater the risks will be for geological hazards.

The report also noted that the rising level of the Three Gorges reservoir is reviving old landslide fissures and that these fissures could become active and move again.

According to another media outlet, the New Tang Dynasty Television (NTDTV), residents in one town along the banks of the Three Gorges reservoir have recently received evacuation warnings to move to higher ground. Three days before releasing the evacuation warnings, a survey found that more than 1.08 billion cubic feet of old landslide bodies, which is land formed by previous landslides, are at risk of being destabilized because of the rising water.

NTDTV also reported that in the Chongqing municipality the rising reservoir has caused nearby mountainous areas to become unstable.

The report by Caijing comes as government officials are eager to raise the Three Gorges reservoir to its maximum height of 175 meters (574 ft) above sea level. Once the reservoir hits 175 meters, the dam will be capable of producing the maximum amount of power.

At the current water level of 171 meters, only 11 of the dam’s 26 hydropower generators are operating, reports the BBC.

Officials have been slowly raising the level since September 15th, but have recently had to postpone the process—which was originally supposed to be completed by the end of October—because a severe drought downstream has resulted in more water than expected being released through the dam. Probe International recently reported that political and social pressures have been behind the officials’ decision to release more water to drought stricken regions downstream.

Also because of the drought, less water is running into the dam’s reservoir. “Officials said 35% less water flowed into the reservoir in October compared to the same month in 2008,” says a report by the BBC.

Now, officials in charge of the dam are uncertain when the reservoir will reach its maximum height. Last year, officials in charge of the dam were forced to stop raising the reservoir at 566 feet after the threat of landslides became serious.

“We hope the political pressure to complete the project by filling it to its maximum height will not take precedence over the safety of residents living along the river,” says Probe International’s Executive Director Patricia Adams. “This should be taken as another sign that this dam was a mistake to begin with.”

UPDATE: A recent story from the Associated Press says the threat of landslides is a major factor in the dam officials’ decision to stop raising the dam.

Yang Yong, a Sichuan-based geologist who has followed the dam project closely, said he believes the renewed threat of geological disasters may have been serious enough to delay the final phase.

“Dealing with drought is a quite obvious reason, but I suspect that the potential geological threat is also a factor in stopping the water from rising,” he said. “I think with the rise of the water level, the geological movement around the area is becoming more and more frequent. The government was quite aware of the problem.”

Probe International, November 9, 2009

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