Trends and Innovations
Rivers in Chains
Twenty years in the making, Chinas ambitious and controversial Three Gorges Dam project is now nearing completion. Easily the largest hydroelectric project in the world, the massive dam has been a lightning rod in the ongoing conflict between energy needs and environmental impact, not only within China but also across the globe. Chinas approach to the project forcing more than 1 million people living in the flood zone near the new reservoir to move has also angered many, who argue that the resettled villagers had no input on the project and no chance to complain.
A small ship sails upstream through the Yangtze River in China, which is nearing completion of the Three Gorges Dam. Photograph is courtesy of Fred Schwab.
Still, although the projects sheer size and prize tag $30 billion (U.S.) render it unique, it is only the latest in a chain of some 20,000 dams that currently harness Chinas rivers. And as other rapidly developing countries in southern and southeastern Asia, such as India and Burma, are lured by the promise of clean hydroelectric power, the Three Gorges Dam is likely to be only the first in a spree of controversial dam projects in the region.
The Yangtze River, 6,300 kilometers long, runs across the entire width of China, from the Qinghai-Tibet Plateau to the East China Sea. The Three Gorges Dam, 2 kilometers wide and 200 meters high, spans the Yangtze at Sandouping and creates a 600-kilometer-long reservoir along the river stretching back to Chinas largest city, Chongqing. At its peak, the dam will be capable of generating 18,200 megawatts of power 1.3 times more than the worlds next-largest dam, at the border between Brazil and Paraguay.
In June, Chinese engineers finished construction on the massive main wall of the dam and blasted away the last temporary barrier that held back the Yangtze River. By 2009, when the last turbine power generators are installed, the dam will be fully operational and will provide up to one-ninth of Chinas rapidly growing power needs, as well as help to control flooding, Chinese authorities say.
With the dam, China is determined to lighten its dependence on coal which will, in turn, reduce the countrys greenhouse gas emissions, Chinese officials say. Furthermore, the dam, the government says, will reduce the Yangtzes cyclic floods from one every 10 years to one every 100 years, saving thousands of lives and billions of dollars in damages.
Critics of the project, however, say that the dam could also become a giant trap for industrial pollutants and human waste, rendering the reservoir a cesspool. Sediment from the silty Yangtze is also likely to accumulate, clogging the dam and reducing its efficiency (see Geotimes, August 2003).
Its silting now, and that could continue a lot faster than projected, says Vaclav Smil, a professor of geography at the University of Manitoba in Canada, and an expert on Chinese energy and environment. The amount of sediment that would enter the river was originally estimated in the 1950s by Soviet engineers, Smil says. But after decades of deforestation, removing the trees that once protected stream banks from erosion, the rate at which sediment enters the river is very different now. Although China has issued an order to stop and desist deforestation, he adds, nobodys going to listen.
To combat the sedimentation and pollution issues, China has several contingency plans in place. In July, a sanitation ship began circulating through the reservoir, gobbling up garbage to keep it from entering the generators. The Chinese also have a plan to construct a series of smaller dams upstream of the main wall to catch the silt before it enters the reservoir, Smil says.
But, Smil says, the long-term effect of the dam on Chinas environment is difficult to predict. How quickly sedimentation might clog the dam depends on both precipitation and deforestation/reforestation along the river, and whether the reservoir becomes cleaner or filthier, he says, will simply depend on how much junk they put into the water. With so many variables, the dams full impact will not be clear for many years, Smil says.
Nutrients in the East China Sea, however, have already changed significantly since the reservoir was filled in 2003, says Gwo-Ching Gong, a marine ecologist at the National Taiwan Ocean University in Keelung. From 1994 to 2004, Gong and his team measured silicon, nitrogen and chlorophyll indicators of the health of the ecosystem in the East China Sea.
The dams most lasting effect was on the levels of silicon, which primarily enters the sea in sediment, Gong says. After the dam was filled, less sediment reached the sea, considerably reducing how much silicon the waters contained relative to nitrogen. Altering that balance of available nutrients could ultimately change which species flourish in the East China Sea, dramatically affecting its food web structure, the team reports in the April 15 Geophysical Research Letters.
Meanwhile, as the Three Gorges Dam nears completion, China is forging ahead with other dam projects that continue to stir up controversy. Several projects, including a second massive dam to be built on the Yangtze, 1,500 kilometers upstream of the Three Gorges Dam, and a proposed dam on the Nu River, have caused an unprecedented public outcry, and approval is pending while assessments are conducted, according to Zhu Guangyao, deputy director of Chinas State Environmental Protection Administration (SEPA). In 2003, SEPA acknowledged environmental concerns by requiring environmental impact assessments for all construction plans.
Thats a step forward, says Grainne Ryder, policy director for foreign-aid and environmental watchdog group Probe International in Toronto, Canada. However, she says, though the assessments have halted construction on at least one dam, other projects including a controversial dam on the Burma/Thailand border are going ahead, despite strong opposition in both China and Thailand. A third Yangtze project was also green-lighted in June.
The same urgent need for cheap, renewable power is spurring a wave of controversial giant dam building in rapidly developing countries elsewhere in the region. A decades-long project in India to build thousands of dams along the Narmada River, including two megadams, has spurred protests over the potential displacement of hundreds of thousands of people, as well as over environmental concerns. Similar issues have plagued Indias plans to build a dam on the Indus River in the disputed Kashmir region in the northeast, which could double Indias current hydroelectric output. Burma is also building a series of hydroelectric dams on its Salween River, a project that critics say is as much a political strategy as an energy strategy because much of the land that will be flooded is populated by an ethnic minority.
Three Gorges has done a lot to encourage gigantic dam building by making these mammoth projects appear profitable, Ryder says. Its a real problem of scale, she says. The environmental cost and damages just become unmanageable. Furthermore, she adds, governments focusing their resources on these large centralized projects will be left behind in terms of developing clean, new technologies.
These projects, though displacing many, are also a sign of a countrys growing pains, Smil says. Indeed, facing growing power needs, the United States went through its own spate of dam building in the last 100 years, he says. The Chinese started kind of late, thats all.
The sheer scale of the Three Gorges Dam project, however, does distinguish it from past U.S. projects, Smil adds. Its just huge, thats the thing. Its the number of people that it will affect and in the long-term, its much more unpredictable.