Two of the most populous
nations—China and India—are building hundreds of dams in a violently active
geologic zone
By Madhusree Mukerjee | Jul 14, 2015
Earlier this year earthquakes in
Nepal leveled thousands of buildings, killed upward of 8,500 people and injured
hundreds of thousands more. The magnitude 7.8 and 7.3 temblors also cracked or
damaged several hydropower projects, underscoring another imminent danger: dam
bursts. More than 600 large dams have been built or are in some stage of
construction or planning in the geologically active Himalayan Mountains, but
many are probably not designed to withstand the worst earthquakes that could
hit the region, according to a number of seismologists and civil engineers.
Should any of the structures fail, reservoirs as large as lakes could empty
onto downstream towns and cities. A collapse of Tehri Dam in the central
Himalayas, which sits above a fault, would, for instance, release a wall of
water about 200 meters high, slamming through two towns. In total, the flooding
would affect six urban centers with a combined population of two million.
More powerful earthquakes are indeed
likely to strike the Himalayas in coming decades, seismology models show. The
Indian subcontinent is pushing under the Tibetan Plateau at roughly 1.8 meters
per century, but it regularly gets stuck; when the obstruction gives way, a
section of the Tibetan plate lurches a few meters southward and releases the
pent-up energy in an earthquake. The Nepal earthquakes also destabilized the
region to the west, notes Laurent Bollinger, a seismologist at the French
Alternative Energies and Atomic Energy Commission. Destabilization makes a
great earthquake, which is defined as having a magnitude of 8.0 or higher, more
likely to occur sooner rather than later. Other studies indicate that the
earthquakes released only a mere fraction of the stress of this fault line,
which is expected to readjust with quakes of equal or higher magnitude.
“Whether they'll break now, in an 8 or wait another 200 years and then give way
in an 8.7, one cannot say,” says seismologist Vinod K. Gaur of the CSIR Fourth
Paradigm Institute in Bangalore.
Such seismically active regions are
exactly where hundreds of dams 15 meters or higher are either under
construction or being planned, most of them to supply hydropower to India or
China. Any dam being built during this government-funded boom, as well as those
already completed, must be able to withstand the strong ground shaking of an
extreme earthquake, says Martin Wieland of the International Commission on
Large Dams, a group of engineers that makes recommendations for structural
standards. Although every nation has its own regulations, India and China are
secretive about their dam designs when it comes to public scrutiny. Independent
engineers rarely are allowed to evaluate the robustness of the structures, and
when they are, the results can be unsettling. For example, Probe International,
a Canadian environmental research organization, reports that designers for
China's Three Gorges Dam used “the most optimistic interpretation possible” of
seismic shaking. Similarly Tehri Dam never underwent realistic simulations,
asserts Gaur, who served on its oversight committee, along with civil engineer
R. N. Iyengar, formerly of the Indian Institute of Science in Bangalore.
Government-affiliated scientists and engineers claim that Tehri Dam can survive
an 8.5 shock, but outside experts are not so sanguine. Any of hundreds of dams
could be in danger of bursting when the next big one hits. If that were to
happen during monsoon season, when the dams are full, the consequences could be
catastrophic.
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Local corruption can complicate
matters, enabling contractors to get away with using substandard materials or
deviating from mandated parameters. A 2011 study published in Nature
found that an overwhelming majority of deaths from building collapse in
earthquakes occur in corrupt countries. What is more, Transparency International, a nongovernmental
organization that highlights corruption, identifies public construction works
as one of the world's most bribery-prone industries—with dams being of special
concern. Scandals involving dam projects have roiled both India and China, to
the extent that the former Chinese premier, Zhu Rongji, coined the evocative
term “tofu construction” to describe a defective dike.
A handful of scientists who
understand the hidden dangers of the Himalayas have taken the lead in arguing
for realistic, undisguised assessments aimed at protecting the region's
population, though only with limited success. In a case brought by
environmentalists against Tehri Dam, the Supreme Court of India sided with
government scientists to dismiss safety concerns. And in 2012 seismologist
Roger Bilham of the University of Colorado Boulder was deported from the New
Delhi airport, in part, he says, for his unwelcome prediction that the
Himalayas can sustain a magnitude 9.0 earthquake. Bilham contends that the
Indian government has since discouraged foreign collaborations in seismology.
For now, all concerned parties can
do is call attention to the problem. “Sunshine is the best disinfectant,” says
Peter Bosshard of International Rivers in Berkeley, Calif. “Without public
scrutiny, it is much easier to get away with cutting corners.” Given the
stakes, more than sunshine will be necessary: the next great earthquake in the area
may well result in a man-made tsunami.
This article was originally
published with the title "The Impending Dam Disaster in the Himalayan
Mountains."
Original article is from Scientific American
Map of dams in the Teesta River basin is from here
Praful Rao,
Kalimpong
Dist Darjeeling
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