China's Three Gorges Dam, by the Numbers
for National Geographic News
|June 9, 2006|
Using enough explosives to level 400 ten-story buildings, China demolished the last barrier holding back the mighty Yangtze River from the Three Gorges Dam on Tuesday, according to government- controlled media.
At 1.4 miles (2.3 kilometers) long, Three Gorges is one of the world's largest dams, and one of the most controversial public works in modern times.
200 Tons of Explosives
Demolition experts used some 200 tons (181 metric tons) of explosives to destroy the final Three Gorges cofferdama temporary construction that had allowed builders to finish the dam's massive main wall.
The blast created some 243,278 cubic yards (186,000 cubic meters) of concrete rubble.
The main dam's construction was completed last month amid much fanfare.
"This is the grandest project the Chinese people have undertaken in thousands of years," Li Yongan, general manager of the Three Gorges Corporation, told the London Times on May 20.
At its peak the construction team numbered some 26,000 Chinese and foreign employees.
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Dam First Proposed in 1919
Sun Yat-sen, founder of the Republic of China, first suggested a dam on the Yangtze River in central China's Hubei Province. He believed the structure could protect river communities from deadly floods.
Communist leader Mao Zedong (Mao Tse-tung) also supported the concept, but construction didn't begin until 1993, 17 years after Mao's death.
The project will flood the three gorges that give the dam its name: the Qutang, Wu Xia, and Xiling. They stretch for some 124 miles (200 kilometers) along the upper and middle reaches of the Yangtze and are renowned for their scenic beauty.
New "Great Wall" Spans River
The dam is some 1.4 miles (2.3 kilometers) long and 607 feet (185 meters) tallfive times larger than the U.S.'s Hoover Dam.
Construction workers used some 21 million cubic yards (16 million cubic meters) of concrete in the structurea world record.
Upstream of the dam, the reservoir's water level is presently 456 feet (139 meters) above sea level, and it's expected to rise quickly. The 410-mile-long (660-km-long) reservoir will eventually be flooded to 574 feet (175 meters) above sea level.
A Hundred Lives, Billions of Dollars
Chinese state media reports that over a hundred workers died during the lengthy construction project.
Economic costs also ran high. Official reports place the price tag in the 24-billion-U.S.-dollar range. Critics say that actual costs could be several times the stated amount.
Over a Million People Displaced
The dam's 410-mile-long (660-kilometer-long) reservoir will flood about 244 square miles (632 square kilometers) of landincluding well over a thousand towns and villages.
Some 1.3 million people (another disputed number) have been or will be relocated.
The Three Gorges plan includes compensation for the dispossessed, such as payments and new homes and jobs. But these efforts have been plagued by widespread local corruption and complaints that funds aren't reaching the intended recipients.
Dozens of architectural and cultural sites will also disappear under the reservoir. Among the most notable are relics of the ancient Ba people, who lived in the region some 4,000 years ago.
300,000 Killed in 20th-Century Floods
Chinese authorities estimate that some 300,000 people were killed in the 20th century's largest Yangtze River floods.
Officials believe that the dam will protect some 15 million people from such deadly waters, as well as 1.5 million acres (607,000 hectares) of farmland.
The wall is built to weather floods of a once-in-a-century severity. But some scientists have expressed concern about earthquake activity in the area, and the unlikely event of a breach could have catastrophic consequences.
50 Percent Drop in Delta Sediment
Environmentalists have warned that the dam will reduce downstream nutrient and sediment flow and seriously impact neigboring river and seacoast ecosystems.
A study published in the April 2006 issue of the journal Geophysical Research Letters suggests that such changes may already be underway.
Researchers reported that ratios of silicon to nitrogen in brackish coastal waters fell from 1.5 in 1998 to 0.4 in 2004. Sediment loading was found in places to be half of pre-dam levels.
Such changes could harm plentiful coastal fishing grounds and subject tidal wetlands to increased erosion.
18,000-Megawatt Turbine Target
Twenty-six turbines (scheduled for operation in 2008) are designed to produce more than 18,000 megawatts of electricitytwenty times the power of Hoover Dam.
In 1993 that figure was thought sufficient to provide an amazing 10 percent of China's total energy needs. During years of construction, however, the nation's growing appetite for power has reduced that number to perhaps 3 percent of the current demand.
44,000 Tons of Cargo Passed Dam Last Year
Last year some 44 million tons (40 million metric tons) of cargo were transported via the Three Gorges Dam. That's up from 14.75 million tons (13.4 million metric tons) in 2003, when the reservoir first began storing water.
Dam proponents stress that the dam will be a boost for Yangtze River trade, which accounts for some 80 percent of China's inland shipping.
Higher water levels will allow larger vessels to ply the river, travel faster, and motor from Shanghai, at the river's estuary, all the way to Chongqing, on the Yangtze's upper reaches.
Ten Million Tons of Garbage
The dam has so far blocked an estimated ten million tons of plastic bags, bottles, animal corpses, trees, and other detritus that otherwise would have flowed out to sea.
Engineers have created an interesting solution to prevent the trash from damaging power generatorsa giant garbage-lapping "tongue."
The Shanghai Daily reports that a rolling track, like a moving sidewalk, will feast on the refuse from its platform atop a garbage boat. Engineers say that the device can consume some 392 cubic yards (300 cubic meters) of garbage an hour.
But the tongue may be useless against another form of pollutioncontaminated water.
The reservoir flooded factories, mines, dumps, and other potentially toxic sites. Volumes of human waste and industrial refuse flow into the now dammed river from communities like Chongqing, and some environmentalists warn of serious water contamination issues.
So far, the Chinese government's Yangtze River Water Resources Committee says, water qualities upstream of the dam have remained unchanged since natural water flow was stopped in 2003. Authorities tout new treatment facilities targeted at reducing the level of pollutants entering the water.
86,000 Dams and Counting
The controversies surrounding Three Gorges Dam are sure to be played out again, because the Chinese dambuilding business is booming.
Three Gorges may itself necessitate the building of several new dams.
"Ultimately the life of this dam is very limited, unless they build other dams to prevent it from silting up," said Jennifer Turner, coordinator of the China Environment Forum at the Woodrow Wilson International Center for Scholars in Washington, D.C.
In other words, Three Gorges could become clogged along its upstream wall with sediment that would normally be washed downriver and out to sea.
"There are a dozen more dams planned further upstream, and they want to end up at Tiger Leaping Gorge. That's significant in terms of the future destruction of parts of the river that are free flowing," Turner said.
"Tiger Leaping Gorge is an area that's symbolic of China. It's like the Grand Canyon."
China already boasts the world's largest number of dams86,000 and counting. The debate over where and how others are built could have huge consequences for China's rivers and beyond.
"In general, the central government has tried to push for more public participation but [the federal government is] not a monolith," Turner said, noting the often primary importance of regional and local officials.
"It's hard, but who knows? The dam issue could lead to more openness in environmental policy and decision-making in China."
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