By Hu Yinan, China Daily
2010-07-23
BEIJING - The flood control capacity of the Three Gorges Dam, the world's
largest hydropower project, is designed to be limited, a senior engineer
said on Thursday amid mounting concerns over the project's ability to
manage floods.
The multi-billion dollar dam was designed to withstand floods with water
flow of 83,700 cubic meters per second, covering the Jingjiang River area
and the Chenglingji region in Hubei and Hunan provinces, Zhao Yunfa,
deputy director of the China Three Gorges Corp's cascade dispatch center,
told China Daily.
"The dam's flood-control capacity is not unlimited it has a capacity of
22.1 billion cu m and protects, by design, a limited area any flood with
water flow exceeding 122,000 cu m per second would put the dam's own
safety at risk," he said.
As China's main reservoir on the Yangtze River, the dam on Tuesday passed
its first and largest test by sustaining a water flow greater than the
flood of 1998, which killed 4,150 people across the country.
The flow of water into the dam's reservoir peaked at about 70,000 cu m per
second. The dam, which was completed in 2008, discharged water at about
40,000 cu m per second.
Zhao's explanation came amid growing concern over the controversial dam,
which officials hope would play a pillar role in flood control and clean
power generation.
In the past few days, members of the public have been hotly debating
online posts comparing four reports of the dam's flood-control capacity.
The first, released in June 2003, claimed that the dam "could fend off the
worst flood in 10,000 years". The second, dated four years later, changed
that number to "the worst flood in 1,000 years". In October 2008, the
number was again modified to "the worst flood in 100 years."
On Tuesday, a report on State broadcaster China Central Television's
website was titled "The Three Gorges Dam's capacity to store floodwater is
limited". The story urged the public not to "lay all hopes on the dam".
In an exclusive interview with China Daily that same day, China Three
Gorges Corp's chairman Cao Guangjing said he can "absolutely guarantee"
that the dam is capable of withstanding "the worst flood in 100 years".
Cao, an engineer with the corporation since 1985, said the dam's
flood-control facilities are "complete and need no adjustment".
Instead, the immediate focus of the work is on ways to improve weather
forecasting ahead of the next major flood-control test, which will likely
take place some time in August, he said.
Liu Ning, vice-minister of water resources, earlier praised the dam, which
was completed in October 2008, as "instrumental" in China's flood control
efforts.
Cao said the dam is able to do much more. "The peak flow this time was
historical. But the frequency, peak period and volume of water were all
comparatively limited - the worst in about 20 years. The dam is far from
displaying its full potential," he said.
China had spent 181.5 billion yuan ($26.5 billion) on the dam project by
the end of 2008. But critics claim that the project has caused, or will
cause, consistent landslides and severe erosion downstream.
Cao, 46, dismissed the allegations as "nonsense". All these issues were
addressed in preliminary feasibility studies from years ago, he said. The
project began in the early 1990s and billions of yuan have been invested
to preventing possible ecological disasters, he said.
"Extreme climate change and large natural trends are far beyond the
control of the Three Gorges Dam project," Cao said.
The dam, which spans the Yangtze River, China's longest river, in Yichang
city of Hubei province, has a capacity of more than 20 billion cu m and
its water level can rise to 175 meters.
Its monitoring systems cover 60 percent of the upper reaches of the
Yangtze, which incorporates an area of about 1 million square kilometers.
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