Trouble on the Yangtze

Trouble on the Yangtze
By Jane Qiu
Science
20 April 2012

http://www.sciencemag.org/content/336/6079/288

YONGSHAN, CHINA�Among the hundreds of fish species that call the
upper Yangtze River home is the largemouth bronze gudgeon. The species
spawns in the rapids of this rocky waterway�also known as the Jinsha
River�which descends from the Tibetan Plateau through the mountains of
western China. Its eggs and larvae are kept afloat by the swift current
until they hatch and mature hundreds of kilometers downstream. "They
have evolved to live in fast-flowing rivers," says Cao Wenxuan, an
ecologist at the Institute of Hydrobiology at the Chinese Academy of
Sciences (CAS) in Wuhan.

But with dozens of new dams planned for the Yangtze system, that
habitat will soon change. Last month, preparatory work began on the
controversial Xiaonanhai Dam, with more projects to follow. Within a few
years, the Jinsha will slow to a sluggish pace and its temperature will
drop as a series of large dams release cold bottom water from their
reservoirs into the river. Along with other endemic fish species, the
largemouth bronze gudgeon may spawn up to 3 months later, and soon
after, its eggs and larvae may sink to the bottom and die from lack of
oxygen. For species already threatened by the Three Gorges Dam
downriver, Cao says, the new series of hydropower dams will "take away
their last refuge."

Last year, the central government solidified plans to increase Chinas
reliance on non�fossil fuel energy from the 2010 level of 8% to 15% of
the energy mix by 2020. Nearly two-thirds of that target will come from
hydropower�an increase on par with adding nearly one Three Gorges Dam
a year. "The scale of hydropower development in China is simply off
the charts," says Edward Grumbine, an environmental policy researcher
at CASs Kunming Institute of Botany in Yunnan Province. Ecologists say
Chinas hydropower push will threaten already-taxed ecosystems in the
upper Yangtze.

Central to the spurt of construction is a 770-kilometer-long stretch of
the lower Jinsha River flowing through Sichuan and Yunnan provinces.
Last June, China announced an injection of $63.4 billion for hydropower
in the region to cover four massive dams with a total capacity of 43,000
MW. "Its worrying to see so many proposed large dams, one immediately
after another," says Zhang Xiaodong, deputy director of the China
Earthquake Networks Center in Beijing.

In addition, three large dams are under construction and five are
planned on the 560-kilometer-long middle Jinsha, with more planned for
the 960-kilometer-long upper reach. At a combined height of 2
kilometers, the dams will convert "the rapidly flowing Jinsha River
into a series of stepped lakes with few free-flowing sections," says
Liao Wengeng, deputy director of the National Research Center for
Sustainable Hydropower Development (NRCSHD) in Beijing. Also tagged for
development are Yangtze tributaries such as the Yalong, Min, and Dahu
rivers.

As construction of the Three Gorges Dam got under way in the 1990s,
ecologists submitted petitions to the central government calling for an
upstream reserve to protect fish populations. The result was the Upper
Yangtze River Rare and Endemic Fish Reserve, a 500-kilometer-long
protected stretch of river that includes 350 kilometers of the Yangtze
mainstream. The reserve became a critical habitat for some 190 fish
species�including the critically endangered paddlefish and the Yangtze
sturgeon (_Science_, 1 August 2008, p. 628 [10]).

In 2005, officials sliced off 150 kilometers of the upriver portion to
make way for the Xiangjiaba and Xiluodu dams. Now the Xiaonanhai Dam
will chip away at the reserve even further. At a cost of $3.8 billion,
the dam is expected to generate 1750 MW of electricity at its
completion. Officials in Chongqing, the municipality overseeing the
project, say that it will alleviate power shortages and boost the local
economy. But it will also create a nearly 100-kilometer-long reservoir
in the heart of the upstream protected area.

For years, ecologists have voiced fierce opposition against the
Xiaonanhai Dam. But the battle was lost last December, when Chinas State
Council green-lighted Chongqings request to shrink the reserve. Road
building and other preparation began 29 March. Critics like Fan Xiao,
chief engineer at the Sichuan Bureau of Geology and Mineral Resources in
Chengdu, fear that Xiaonanhai will pave the way for two additional
upstream dams proposed by Sichuan authorities in the reserve area. And
that could mean the end for the paddlefish, the Yangtze sturgeon, and
other endemic fish: "The reserve would exist only in name," he says.


GEOLOGICAL MINEFIELD

Driving on the narrow road clinging to a cliff above the Jinsha River
is not for the fainthearted. It circles mountains that have risen out of
tens of millions of years of thrusting and folding of Earths crust,
overlooking a steep valley carved by the roaring river. Scars left by
recent landslides cut across facing slopes.

Critics fear that Chinas hydropower expansion will collide with this
stark topography. Crisscrossed with active faults hundreds of kilometers
long, the region is "much more geologically complex than the Three
Gorges," says geologist Guo Shunmin of the China Earthquake
Administrations Institute of Geology in Beijing. Earthquakes of
magnitude 7 or 8 are not uncommon. "A lot of the reservoirs will have
active faults beneath them," he adds.

Given that some evidence links construction of the Zipingpu Dam to the
2008 Wenchuan earthquake (see sidebar, p. 291 [11]), "there should be
studies on the effect of water impoundment on active faults beneath the
[Jinsha area] reservoirs," says Hu Xianming, a geophysicist at the
Sichuan Seismological Bureaus Institute of Reservoir-Induced Seismicity
Research in Chengdu. The current safety evaluation, however, involves
only surveys to avoid building dams on active faults.

Compounding the problem is the up to 2 meters in precipitation the
Jinsha region gets every year. In monsoon season, torrential rains can
tear apart steep slopes. Massive landslides have blocked the Jinsha for
days at a time in the past, says Yang Yong, director of the
environmental group the Hengduanshan Society in Chengdu.

Changes in water temperature will be stark as well. The 278-meter-high
Xiluodu Dam will cool water temperature by an average of 1.5�C for the
months of March through September, according to the projects
environmental impact assessment (EIA). Deep reservoirs stratify water
into layers of different temperature, with the coldest near the bottom.
Water from the cold bottom layer will be released downstream, Liao says.
Most fish species spawn in April or May, when the water warms to 16�C
to 18�C. After the four dams on the lower Jinsha are built, the EIA
says, downstream portions of the river wont reach such temperatures
until 2 to 3 months later. That will "hamper fish reproduction,"
Liao says. He points to the Three Gorges Dam: With spawning delayed by
over a month, downstream carp populations have been decimated.

The problems brought on by that earlier dam are well documented. The
river dolphin, or _baiji_, has been functionally extinct since 2007,
and ecologists fear that the finless porpoise, or _jiangzhu_, may soon
follow it.

Also of concern is silt accumulation: Sediment retention in the
reservoir means the clearer downstream water can cut the riverbed deeper
and lower water levels in lakes fed by the Yangtze. In January, Poyang
Lake, Chinas largest freshwater lake, was hit by the worst drought in 6
decades: the water level dropped to a mere 8 meters, and much of the
lake has become a plain of cracked mud. Such problems will snowball with
"a cascade of upstream dams," Liao says.

A STACKED DECK

Some hydrologists say that optimizing dam operation could alleviate
problems with downstream water supply. But many are unconvinced. With so
many new dams, says Guo Qiaoyu, director of The Nature Conservancys
Yangtze River project, "it will be extremely difficult to ensure
proper coordination between provinces and companies that operate the
dams."

With the new hydropower boom, criticism of Chinas EIA process is
mounting. By law, dams cannot be constructed in nature reserves or their
buffer zones. But the government is all too willing to redraw the
boundaries to accommodate hydropower projects, some say. The Xiaonanhai
Dam in particular, Guo says, is "yet another example of the countrys
disregard for the environment."

Critics say EIA committee members are often paid for their services by
dam projects and deliver favorable assessments in order to be invited
back. "The EIA is just about friends evaluating each others
projects," says Wang Mingna, a hydrologist at the Chinese Institute of
Water Resources and Hydropower Research in Beijing. Scientists warnings
"often fall on deaf ears," adds ecologist Yang Junxing of CASs
Kunming Institute of Zoology.

Adding bias to the schedule, ecologists say, are rules that allow
developers to start preparing for a proposed dam while project
assessment is still under way. And EIAs are too narrow, examining
projects in isolation, points out He Daming, an ecologist at Yunnan
University, Kunming. "Even if the impact of individual dams is
acceptable," he says, "the cumulative effects of stacking dams on
top of one another could still be catastrophic."

The science ministry is funding research that takes additive impacts
into account. The Ministry of Water Resources, meanwhile, may soon
improve the EIA process, says Yu Xuezhong, chief engineer at the NRCSHD.

But such measures may come too late for the upper Yangtzes beleaguered
fish species. Ecologists are scrambling to set aside small
sanctuaries�in small tributaries near their current habitats, for
example. The goal, Cao says, is to "save as many fish species as we
can. All we can hope for is to slow down the extinction rate."

Jane Qiu is a writer in Beijing and London.
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