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Geological Risks Emerge at Three Gorges Dam

04-09 17:42 Caijing

Rising water levels at the Three Gorges Dam have caused the deterioration of the riverbanks and threatened local communities.

By staff reporter Deng Hai


(Caijing.com.cn)A severe landslide near the Three Gorges Reservoir in Yunyang County, Chongqing City forced 55 residents to evacuate the region.


The Chongqing municipal government said at a press conference on April 7 that state work teams and experts have confirmed the landslide will not block the flow of the Yangtze River or interfere with river navigation. However, the region has been put on yellow alert, requiring intensified supervision and technical support.


The sliding surface of the Yunyang landslide covered 100,000 square meters at an average depth of 35 meters, totaling 3.6 million cubic meters of mud. But other pieces have not broken off yet, according to China Geological Survey expert Yin Yueping. “There are gaps in surface of the riverbank and the bank is deteriorating,” he said.


Since the reservoir’s water level rose to 175 meters in September 2008, the surrounding region in Chongqing has identified over 100 new sites at risk of geological disaster, now totaling 150 sites in the region encompassing 45 million cubic meters of mud across 13 counties. Geological disasters have already severely damaged eight out of the newly added 100 sites, and affected channel and shipping safety at three other sites.


An expert from the Ministry of Water Resources told Caijing that the dam’s fluctuating water levels are comparable to those during floods that occur on average once every 100 years. But today, 30-meter fluctuations occur about once each year, thereby increasing damage to the riverbank.


The landslides have affected over 9,000 residents and over one million square meters of land, said an official from the Chongqing Municipal Bureau of Land and Resources. The bureau estimated that these landslides have caused economic losses of about 500 million yuan.


After the reservoir began storing waters at higher levels, hydro-geological conditions along the riverbanks deteriorated and became unstable. The number of stable land bodies decreased 37.8 percent, while the number of potentially unstable ones increased 51.7 percent, according to a Ministry of Water Resources internal document.


Many geological disasters remain a serious threat. In the third phrase of the Three Gorges geological disaster prevention plan, 2,977 sites required attention, among which 2,686 were potential landslide sites, but only 355 received treatment.


Most large communities threatened by geological disaster in the Three Gorges area can be moved with government financial support. Small communities, however, are excluded from the disaster prevention plan and thus face such dangers alone.


“When night falls, I hear the rocks rolling down to the Yangtze River, and I can barely fall sleep,” said a villager in Badong County, a small community along the Three Gorges dam. “When I wake up, I go out and examine the surroundings carefully.”


Full article in Chinese: http://www.caijing.com.cn/2009-04-07/110134214.html

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