Three Gorges Dam
Three Gorges Dam
When finished in 2009, the Three Gorges Dam on the Chang Jiang (Yangtze River) will be the largest dam in the world. Spanning 1.2 mi (2.0 km), and standing 600 ft (175 m) above normal river level, the dam will create a reservoir more than 400 mi (644 km) long. The project was designed to control floods, ease navigation, and provide badly needed electricity for China's heartland. The 26 giant turbines in the dam's powerhouse are expected to generate 18,200 megawatts of electricity—equal to 10% of the country's current supply—to support industrialization and modernization in the region. The reservoir will flood the scenic Three Gorges, one of China's most historically significant areas. It also will displace at least 1.3 million people and will flood 150 towns and cities, and more than 1,300 villages.
Proponents of the project argue that China needs the project's electricity for modernization. With dangerous rapids drowned under the reservoir, ocean-going ships will be able to sail all the way to Chongking, nearly 2,000 mi (3,200 km) inland from the ocean. The water stored in the reservoir also will make possible a long-discussed plan to build aqueducts to carry water from southern China to the dry plains around Beijing. Furthermore, annual flooding on the river caused 300,000 deaths in the twentieth century. In 1998, the worst flood in history drove 56 million people from their homes. Planners expect the dam to reduce these floods and eliminate untold misery for the 300 million people who live in the Yangtze River Valley.
The Three Gorges Dam was first proposed in 1919 by Dr. Sun Yat-sen, a revolutionary and founder of the Chinese republic. Later it was championed by Mao Tsetung (or Zedong) who led the country from 1949 to 1976. Mao saw this project as a way to instill national pride and demonstrate China's modernization. Although Mao ordered a full-scale survey and project design in 1955, prohibitive costs together with doubts about the safety and feasibility of the dam have slowed construction. In 1992, Premier Li Peng pushed through the final vote to authorize the project. The first stage of construction was completed in 2002, and flooding of the reservoir will begin in 2003. The water is expected to reach its maximum height by 2009.
Environmentalists criticize the dam on the grounds that it will reduce fish stocks, eliminate 78,000 acres (32,000 ha) of important agricultural lands, and threaten habitats of critically endangered species such as the Yangtze river dolphin, Chinese sturgeon, finless porpoise, and Yangtze alligator. The reservoir will also fill one of China's most important historical and cultural regions, sinking 8,000 archeological sites and historic monuments. Currently, more than 250 billion gallons (nearly a trillion liters) of untreated sewage is dumped into the Yangtze every year. Planners claim that the new cities into which residents are being relocated will have better sanitation than the old river towns. How sewage is handled in these new towns, and how much contamination leeches out of abandoned structures in the reservoir remains to be seen. Environmentalists worry that the reservoir will become a stagnant cesspool, dangerous to both aquatic life and to the millions of people who depend on the river for their drinking water.
Sediment and silt accumulation is another problem to be solved, since tremendous volumes of sediment will accumulate as the silt- and sand-laden Yangtze River slows in the reservoir. Elsewhere in China silt and sand accumulation has decreased reservoir storage capacity nationwide by 14%. Simply controlling river-bottom gravel may require dredging as much as 200,000 m2 of material each year. To reduce sediment accumulation, dam operators plan to let spring floods, which carry much of the annual sediment load, flow through silt doors at the bottom of the dam. They hope this flow will scour out the bottom of the reservoir.
Geologists worry about catastrophic dam failure because the dam is built over an active seismic fault. Engineers assure us that the dam can withstand the maximum expected earthquake , but China has a poor record of dam safety. More than 3,200 Chinese dams have failed since 1949, a failure rate of 3.7% compared to a 0.6% failure rate for the rest of the world. Probably the worst series of dam failures in world history occurred in Henan Province in 1975, when heavy monsoon rains caused 62 modern dams to fall like a line of dominoes. Some 230,000 people died in the massive flooding that followed. Even if the dam is able to withstand earthquakes, giant waves spawned by upstream landslides could easily cause a calamitous dam failure. In 1986, a landslide just a few miles upstream from the dam site dumped 15 million cubic meters of rock and soil into the river. Witnesses reported an 260 ft (80 m) wave rolling down the river. If a wave that size hits the upstream side of the dam with a full reservoir, one geologist predicts a flood "of biblical proportions" as a wall of water races downstream through lowlands where hundreds of millions of people live.
The Chinese government is installing an early warning system to predict landslides, and has banned timber cutting and farming on steep upstream hillsides in an effort to control both landslides and sediment loads in the river. Critics claim that there would be safer and cheaper ways to store water and generate electricity than a single huge dam. Original estimates were that the Three Gorges Dam would cost $11 billion. By 2002, the costs for construction, relocation, and landscape stabilization had risen to $75 billion, and the project is not yet finished. A series of relatively small dams on tributary streams might have been much cheaper and less disruptive than the current project.
In 2002, the first stage of the dam was completed and water started filling the reservoir. By late 2003, the water is expected to reach a height of 438 ft (135 m) above normal river level. Most of the new cities above the final 175 m watermark have already been finished, and relocation of residents is well underway. Destruction and decontamination of cities that will be flooded has also begun.
[William P. Cunningham Ph.D. ]
Hessler, Peter. River Town: Two Years on the Yangtze. New York: Harper-Collins, 2001.
Leopold, Luna. Sediment Problems at Three Gorges Dam. Berkely, CA: International Rivers Network, 1996.
Ryder, Grainne, ed. Damming the Three Gorges: What the Dam Builders Don't Want You to Know. Toronto: Probe International, 1990.
Sullivan, L. R. "The Three Gorges Project: Dammed If They Do?" Curent History 94 (1995): 266–70.
"Three Gorges Dam." Environmental Encyclopedia. . Encyclopedia.com. (January 16, 2019). https://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/three-gorges-dam
"Three Gorges Dam." Environmental Encyclopedia. . Retrieved January 16, 2019 from Encyclopedia.com: https://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/three-gorges-dam
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