UPDATE: The extensive damage done to dams by the earthquake, some have speculated, may lead the government to strengthen its review process for dam building. Meanwhile, concerns that dams may be responsible for seismic activity, persist. See this LA Times story.
A "quake lake," formed by a dam caused by a landslide, has led to the relocation of thousands, who fear that a burst would destroy their crops and their homes. Soldiers with heavy machinery are trying to divert the water.
The human impact of China's most devastating natural disaster in three decades, which is estimated to have claimed at least 12,000 lives, may not be fully known for weeks. Thankfully, no damage has been reported at the Three Gorges Dam, the world's largest, situated some 700 km east of the epicenter (map here). If the quake had affected the dam, the human toll would be even harder to imagine.
The dam sits above some 15 million people (some of whom are already suffering from soil erosion that can lead to landslides). Last September, government officials joined the dam's critics in raising the alarm about potential dangers, among them that the dam itself could trigger quakes as it sits near a number of fault lines. A burst at the Three Gorges, says engineer Philip Bosshard, former president of the San Francisco-based International Rivers Network, would "rank as one of history's worst man-made disasters."
The Three Gorges may be fine, but near Dujiangyan, where some of the greatest loss of life occurred, a number of dams and the surrounding areas are at risk.
While there is no official word yet on the status of those dams, a friend, who met today with researcher-activist Yu Xiaogang, said that at least one of the dams near Dujiangyan has likely cracked. Update: 2000 soldiers have been sent to repair "extremely dangerous" cracks in a dam upstream of Dujiangyan, which "would be swamped" if the dam were breached. The NYT reports that 400 dams have been damaged.
According to Xinhua, Sichuan officials said on Tuesday that "cracks had appeared on the surface of the dam at the Zipingpu [reservoir] and workshops collapsed, while all hydropower generators came to a halt." A command center has been set up at Zipingpu to safely discharge the reservoir's rising waters and ensure that the damage posed no threat to Dujiangyan and the neighboring Chengdu Plain.
Also, from Reuters: "Upstream on the Min river is an important reservoir called Tulong which is already imperilled. If the danger intensifies, this could affect some power stations downstream," He Biao, deputy party chief of Aba prefecture, told reporters. "This is an extremely dangerous situation."
Peter Hessler reminds us at the New Yorker that the damage could have been much worse had an enormous dam project nearby not been canceled in 2003, amidst concerns by the local seismological bureau and complaints of local citizens.End update
Also slightly damaged is a different kind of earth-changing project: the stunning, 2000 year old Dujiangyan Irrigation System, a UNESCO World Heritage site that is the world's oldest and only surviving no-dam irrigation system. This could put a very large area of agricultural land at risk. (Also damaged in the city of Shifang were two chemical plants, burying 100 workers and causing a leak of liquid ammonia. The epicenter of the quake was near the world famous Wolong Panda Reserve, but the pandas are reportedly safe.)
Though modern dams, like nuclear reactors, are built to higher earthquake standards than most buildings, standards are not met or cannot always be met in rural China. The town of Dujiangyan has learned this tragically: 900 children were trapped beneath a collapsed school building built just 10 years ago, while older buildings nearby remained standing.
Even if the building had been built to earthquake standards, that may not have been enough: ranking a 10 or 11 on the Mercalli intensity scale, the quake exceeded expectations for local seismic activity by a third.
Though Monday's disastrous earthquake was a result of tectonic collision, there are fears that the Three Gorges Dam could trigger earthquakes on its own. Its reservoir sits on two major faults, which can be aggravated by changes in water level, and recently relocated residents have reported landslides, mudslides and ominous cracks in the ground. According to a March 2008 article in Scientific American by Mara Hvistendahl,
Engineers in China blame dams for at least 19 earthquakes over the past five decades, ranging from small tremors to one near Guangdong province's Xinfengjiang Dam in 1962 that registered magnitude 6.1 on the Richter scale—severe enough to topple houses.
Surveys show that the Three Gorges region may be next. Chinese Academy of Engineering scholar Li Wangping reports on the CTGPC's Web site that the area registered 822 tremors in the seven months after the September 2006 reservoir-level increase.
Meanwhile, upstream from the Three Gorges along the Jinsha river, a section of the Yangtze, at least a dozen new dams are being built in order to alleviate sedimentation caused by the Three Gorges reservoir. They too lie in the same seismic region as Monday's earthquake. As a geologist told the Guardian in 2003 of the area, "The Jinsha has bad geological conditions, and there is a more severe seismic area upriver from Xiangjiaba [the site of the furthest downstream of the four dams]." Near this site dam projects "should not be encouraged," he said.
A side note: the response to this earthquake reminds us again that tides are shifting in China, as they must, towards more transparency and government responsiveness. The response by citizens illustrates just how powerful and important the internet can be in a country where information is often scarce. And the reaction by government officials like premier Wen Jiabao, who is also a trained geologist, points to growing concerns about how the government responds to natural and man-made environmental disasters.