(April 4, 2012)
A new report finds more than 130 large dams being built in western China
could trigger disaster — earthquakes, even tsunamis — due to their
construction in seismic hazard zones.
More than 130 large dams that China is building in its western region,
an area of high seismicity, are vulnerable to earthquakes or could
induce earthquakes, according to a new report released by the
Canadian-based environmental group Probe International. In a worst-case
scenario, dams could collapse creating a tsunami that would wipe out
everything in its path, including downstream dams, and cause untold loss
of life and property.
To pierce the Chinese government's secrecy over its dam-building, the
Probe report overlays a Chinese map of dam locations with US Geological
Survey earthquake data and a United Nations' seismic hazard map. Probe
also used Google Earth satellite images to confirm the state of
completion of about one-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 sank 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 over M4.9 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 hazard 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 recordkeeping began in 1973, nine
earthquakes with a magnitude of 4.9 or greater have occurred in western
China each year, on average.
Especially worrying in this environment, said Mr. Jackson, is the
cascade-like positioning of the dams which follow one another so closely
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 (about one-third are hydrodams), 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 Probe
International 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.
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, says Patricia Adams, Executive Director of
Probe International, that anger would spill over to the hydropower
industry for threatening ordinary citizens' lives with dangerous dams.
John Jackson is a pseudonym for a geologist with detailed knowledge of
western China who must remain anonymous.
For more information, contact Patricia Adams at
Tel. 1 (416) 964-9223 (ext. 227)
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