China's past dam building has outpaced that of any other society in history. Now its appetite for construction -- more than 130 large dams in western China -- is in a region of high seismicity, with the largest and most active seismic fault systems on the planet. A new report commissioned by Probe International, the organization I head, says the consequences could be disastrous.
There is great risk that the dams will be damaged by earthquakes, or that they will induce earthquakes themselves, says the report, Earthquake Hazards in Large Dams in Western China. In a worst-case scenario, dam collapses could create a tsunami that would wipe out everything in its path, including downstream dams, and cause untold loss of life and property.
Little is known about the seismic risk of China's dam-building because of government secrecy surrounding the dam industry and the country's seismic records. The Probe report overlays a Chinese map of dam locations with US Geological Survey earthquake data and a United Nations' seismic hazard map. Google Earth satellite images were also used to confirm the state of completion of about half of the dams.
According to the report, 98.6% of the dams being constructed in western China are located in moderate to very high seismic hazard zones. The Zipingpu dam, for example, which is now thought to have triggered the magnitude 7.9 Sichuan earthquake in 2008 that killed an estimated 80,000 people, was built in a moderate seismic zone. The force of that quake cracked the dam and shook it so severely that it sunk one metre and moved 60 centimetres downstream.
"The location of large dams near clusters of recorded earthquakes with magnitudes greater than 4.9, and especially when the earthquake focal points are also close to the surface, is cause for grave concern," said John Jackson, a geologist and the report's author.
Earthquakes greater than magnitude 4.9 have been known to damage dams and other structures. Shallow earthquakes (less than 10 km deep) indicate active faults that could be reactivated by routine practices, such as the filling of a reservoir to accommodate flood waters and its drawdown to generate power, he says.
"In addition to the hazards of high natural seismicity in western China, reservoir-induced seismicity is likely to increase the frequency and perhaps the magnitude of earthquakes in this area," he warns.
Western China is known to be a large regional stress field because of the rapid, geologically speaking, northward motion of the Indian subcontinent into western China. This "continental collision" has, for example, lifted seafloor sediments to the top of Mt. Everest and created the Tibetan Plateau. Since detailed record-keeping began in 1973, an average of nine earthquakes with a magnitude of 4.9 or higher have occurred in western China each year.
Especially worrying in this environment, said Mr. Jackson, is the cascade-like positioning of the dams, which follow one another so closely that there is no terrain between them for energy to dissipate in the event of catastrophic dam failure.
"If one dam fails, the full force of its ensuing tsunami will be transmitted to the next dam downstream, and so on, potentially creating a deadly domino effect of collapsing dams," he says.
China is the world's largest hydropower producer with some 87,000 dams and reservoirs, of which nearly half are considered to be dangerous and at risk of collapse.
In the interest of public safety and a sound power sector, the report urges the Chinese government to disclose the details of its current slate of dam construction, and to ensure that a thorough and independent regional seismic risk assessment is done without delay and publicly disclosed.
These views are echoed by one of China's leading geologists, Fan Xiao, Chief Engineer with the Sichuan Geology and Mineral Bureau, who says "the risks described in this study are real and potentially catastrophic for innocent Chinese citizens."
"We owe it to them, as scientists, to investigate and expose these risks immediately," he adds.
Chinese citizens are becoming increasingly vociferous in their outrage over lives risked, and lost, to shoddy standards, most recently in the country's food and high-speed rail industry. Should a dam suffer catastrophic dam collapse, that anger could quickly spill over to the hydropower industry for threatening ordinary citizens' lives.