Dams and Landslides

Three Gorges reservoir hits 175-metre mark, risks begin

(October 26, 2010) China’s massive Three Gorges dam reservoir is finally sitting at its maximum height of 175 metres.

China’s massive Three Gorges dam reservoir is finally sitting at its maximum height of 175 metres, and observers are watching with fingers crossed—worrying over earlier warnings that a higher reservoir may trigger landslides and seismic activity in the region. The two previous attempts to raise the dam’s reservoir to 175 metres—known as it “Normal Pool Level”—were scuttled because of the risk of increased landslides and because officials were pressured to release water to help drought-stricken regions downstream.

With the dam’s reservoir now at the 175-metre mark, the government is expected to declare the “official” completion of the dam.

But many of the environmental problems, such as landslides, that plagued previous efforts to raise the reservoir to its official maximum height, remain. A report from the investigative magazine Caijing last year warned that the number of landslides and other geological dangers will increase if dam officials persist in raising the level of water to its maximum height. The report, citing a research paper by the Chongqing Political Consultative Conference, said the higher the reservoir, the greater the risk of geological hazards.

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

Seismic activity near the reservoir has also increased since officials began filling it in 2003. The 21st Century Business Herald, in a 2003 report, quoted Xu Guangbin, director of the Hubei Seismological Monitoring and Prevention Centre detailing the increased seismic activity since the filling of reservoir: “As many as 1,000 micro-earthquakes have occurred in the Three Gorges reservoir area since June 7, with the biggest recorded at 2.1 on the Richter scale.”

And a 2008 report in Scientific American explained that the reservoir sits on two major faults, the Jiuwanxi and the Zigui–Badong. According to Fan Xiao, a geologist at the Bureau of Geological Exploration and Exploitation of Mineral Resources in Sichuan province, changing the water level will strain these fault lines.

“When you alter the fault line’s mechanical state it can cause fault activity to intensify and induce earthquakes,” he said.

Increased seismic activity and landslides are already having a dramatic effect on the livelihoods and safety of residents living along the reservoir. When officials attempted to raise the reservoir last year, media outlets reported that residents living in towns along the reservoir received evacuation warnings [PDF] to move to higher ground. At the time, one media outlet said that the rising reservoir is causing mountains in the Chongqing municipality to become unstable.

Brady Yauch, Probe International, October 26, 2010

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