(April 16, 2010) Fears of a potential collapse of the Changu dam, once again, highlight the problems of constructing dams in seismically active regions—especially so in China, where the quality of dams has been questioned.
China has been hit with another strong earthquake, this time a 6.9 (7.1 according to the U.S. Geological Survey) tremor with an epicentre near Jiegu in Yushu County on the Qinghai Plateau. Initial reports say the quake has already claimed the lives of over 1,000 people and injured more than 11,000. More than 10,000 soldiers, police, firefighters and medical workers were already in Yushu as of Thursday. The provincial government says it will be supplying 5,000 tents and 100,000 coats and blankets.
Complicating the rescue efforts is the added danger posed by the Changu dam, which was reported to have been damaged by the earthquake and “at the risk of collapse at any time.” According to later reports from the China News Service, the situation has since been controlled, with residents being temporarily settled away from the reservoir. Officials have also lowered the dam’s reservoir level and now say it is no longer in danger of collapsing.
Yet, fears of a potential collapse of the Changu dam, once again, highlight the problems of constructing dams in seismically active regions—especially so in China, where the quality of dams has been questioned. Fan Xiao, a geologist at the Sichuan Bureau of Geology and Mineral Resources, says many of the China’s dams are poorly constructed and pose a serious danger to residents living downstream.
Fan says these dams are time bombs waiting to explode in the event of a serious flood or an earthquake.
Not only do dams become highly hazardous themselves in the event of an earthquake, but large dams are known to trigger earthquakes—a phenomena known as reservoir induced seismicity (RIS).
A number of researchers, (see here, here and here), have suggested that China’s last major earthquake—the Sichuan quake in 2008 that killed nearly 90,000 people—was triggered by the Zipingpu dam reservoir. Though the Chinese government has been quick to deny the possibility that Zipingpu played any role in the Sichuan earthquake; they have been steadfast in refusing to release the micro-seismic data that would shed light on the hydro-geological forces that were unleashed on an unsuspecting public on May 12, 2008.
Despite this growing professional and public concern that large dams can trigger earthquakes, Chinese power companies are currently on a dam building frenzy in China’s south-west region, which is well-known as a seismically active region.
According to International Rivers, several very large dams are currently being built on the middle reaches of the Yangtze, downstream of Yushu County, where this week’s earthquake occurred. Two hydropower projects— Nieqiahe and Lagong—have already been built on the Upper Yangtze in Yushu County and eleven more hydropower projects are under active consideration on the same stretch of the river. In addition, the 302-meter-high Tongjia Dam is being considered as the starting point of the Western route of the South North Water Transfer scheme in Yushu County. There are also plans to build at least 81 large dams on the upper reaches of the Yangtze, the Mekong and the Salween rivers in Qinghai Province and Tibetan Autonomous Region.
Brady Yauch, Probe International, April 16, 2010