Projects are strong enough to withstand a rare “thousand year” earthquake, say China Three Gorges Corporation officials: “no need to worry”. Experts beg to differ.
The Chinese-language version of this article was translated into English by Probe International
Chinese enterprises have built hydro dams in Nepal and in China’s seismically active regions in China, and now the powerful earthquake that occurred in Nepal [on April 25, 2015] has reignited concerns about dam safety both in and outside of China.
Zhai En, Chief Engineer of Civil Infrastructure and Director of Chief Engineer’s Office for China Three Gorges Corporation, said that the construction of hydropower projects by the Three Gorges Group in Nepal will continue as planned.
“No country in the world can reduce seismic risk to zero but most Chinese-built dams are built to withstand the largest earthquakes that strike only every ten thousand years, which people don’t need to worry about,” he said in an interview with the Shanghai-based ThePaper.cn at the World Hydropower Congress in Beijing on May 20.
“From the preliminary assessment made by our staff before their withdrawal (from Nepal), the three hydro projects by the Three Gorges Group in Nepal have not been significantly affected, but we will do more detailed assessments on these projects before resuming the construction for the safety consideration,” Zhai added.
The Three Gorges Group is currently building three hydro projects in Nepal — the Upper Madi, Upper Trishuli 3A and Rasuwagadhi dams. The 7.8-magnitude earthquake that occurred on April 25 killed two company workers. All remaining workers returning to China the same day.
When interviewed, Fan Xiao, geologist and former chief engineer of the Regional Geology Investigation Team of the Sichuan Geology and Mineral Bureau, said that Nepal, northern India, Bhutan, and South Tibet all belong to the Himalayan seismic activity zone, where building hydro dams is risky. The larger the project, he claims, the greater the risks and secondary disasters will be.
Yang Yong, geologist and director of the Hengduan Mountain Research Institute, agreed, pointing out that the the area around the Tibet-Nepal border was also affected by the (April 25) earthquake. He suggested that the Chinese government should seriously reconsider hydropower development in the Yarlung Zangbo Valley. According to Mr Yang, the Yarlung Zangbo Valley is still in the “developmental” stage, and geological processes such as very strong earthquakes, mountain collapses, landslides and other such events frequently occur. This could exacerbate the impact of earthquakes, and increase the risks of hydropower-related disasters.
Responding to previous claims made by the aforementioned experts, Zhai En told ThePaper.cn that the Three Gorges Group had fully taken the seismic factor into account when it planned the Nepalese project. Mr Zhai confirmed that all of their dams in Nepal are made of concrete that can withstand a rare thousand-year earthquake, while the large hydropower projects built in China’s Jinsha Valley are strong enough to withstand an earthquake the magnitude of which strikes every ten thousand years.
“The earthquake-resistant building standards are much higher for hydro dam projects that those set for average buildings. As it’s impossible for hydro projects to get 100% risk-free due to the limitations of current technology and costs, the risk at this level is already close to zero. People can put their minds at ease in terms of the earthquake-resistant capacity of these dams,” the engineer said.
According to the International Commission on Large Dams, globally, no concrete dams have ever collapsed as a result of earthquakes, with the exception of Taiwan, where in 1999, a dam’s sluice was destroyed by an earthquake as the dam was built in a fault zone.
Li Jugen, Secretary-General of China Society of Hydroelectric Engineering, concurs:
“No safety incidents occurred in any of the concrete dams in China’s Wenchuan earthquake, which indicated that all concrete dams in the affected area stood up to the test of the earthquake.”
Mr Li explained that even if part of a dam was damaged due to seismic activity, it could still be repaired and reinforced, making it almost impossible for such infrastructure to collapse.
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