Three Gorges Dam, China

Three Gorges Dam, China crosses the Yangtze River at Sandouping, Yichang, Hubei province, China. The dam’s name refers to the majestic limestone cliffs of the Qutang, Wu, and Xiling gorges, which stretch for about 200 kilometers (124 miles) from Fengjie, in Sichun province, to Yichang, in Hubei province, in China's heartland. The Yangtze is the longest river in Asia and the third longest in the world, running 6,211 kilometers (3,860 miles) from Qinghai Province in the Tibetan Plateau to the East China Sea near Shanghai. The river’s watershed is massive, spanning 1,722,155 (1,070,147 sq. miles) with nearly 400 million inhabitants.

 Christine Yunn-Yu SunMap of the location of the Three Gorges Dam and some of the major cities and provinces along the Yangtze River. Credit: Christine Yunn-Yu Sun

On April 3, 1992, the National People's Congress of China approved the construction of the world's largest and most controversial hydroelectric facility at Three Gorges. The reservoir began filling on June 1, 2003; full power generation of about 22,500 MW is scheduled to  be reached in 2011. Three Gorges will surpass the 14,000MW Itaipú dam located on the Paraná River at the Brazil/Paraguay border.  When finished, the project will have cost 180 billion yuan, or about  30 billion USD.

Scale of Project

The dam wall is made of concrete and is about 2,309 meters (7,575 ft) long, and 101 meters (331 ft) high. The wall is 115 meters (377.3 ft) thick on the bottom and 40 meters (131.2 ft) thick on top. The project used 27,200,000 cubic meters (35,600,000 cu yd) of concrete, 463,000 tonnes of steel, enough to build 63 Eiffel Towers, and moved about 102,600,000 cubic meters (1.342 x 108 cu yd) of earth.

Three Gorges Dam in operation.Three Gorges Dam in operation.

When the water level is maximum at 175 meters (574 ft) over sea level (91 meters (299 ft) above river level), the reservoir created by the Three Gorges Dam is about 660 kilometers (410 mi) in length and 1.12 kilometers (0.70 mi) in width on average, and contains 39.3 cu km (9.43 cubic miles) of water. The total surface area of the reservoir is 1045 km2. The reservoir will flood a total area of 632 km2 of land compared to the 1,350 km2 of reservoir created by the Itaipu Dam. The Three Gorges Dam reservoir is longer than the 560 kilometers (348 mi) length of Lake Superior, but only 1.1 % of the surface area of the lake (82,400 km2) and about 1/700 of the volume of the lake (28700 cu km).

The dam will raise the water level the third time to its designed maximum water level (175 m above sea level) by the end of 2008.

There about 50,000 other dams on the Yangtze River, mostly along tributaries of the main river, that were built in the past 50 years to create freshwater reservoirs. The freshwater storage capacity has skyrocketed from 0.06 cubic kilometers in 1950 to 180 cubic kilometers in 2002. When the reservoir behind the Three Gorges Dam is full, it will add up to 40 cubic kilometers to that total.

Hydroelectricity generation and distribution

The Three Gorges Dam is the world’s largest hydroelectric power station by total capacity, which will be 22,500 MW. It will have 34 generators in total; the first one (No.2 ) started to power on July 10, 2003.  After completion, the expected annual electricity generation will be over 100 Twh.

 Voith Siemens Hydro Power Generation.Runner of a Francis turbine used for the Sanxia (Three Gorges Dam) power plant, China. Credit: Voith Siemens Hydro Power Generation.
Each of the main generators weighs about 6000 tonnes and is designed to produce at least 700 MW of power, which is enough to power a large city. The designed head of the generator is 80.6 m. The flow rate varies between 600 cu m to 950 cu m depending on the head available. The Three Gorges Dam project uses Francis Turbines, among the most efficient turbines made.

Power is sent in three directions. The 500 kV DC transmission line to the East China Grid has a capacity of 7,200 MW. There are three 500 kV DC transmission lines: HVDC Three Gorges-Shanghai(3,000 MW), HVDC Three Gorges-Changzhou(3,000 MW) and HVDC Gezhouba - Shanghai(1,200 MW). The 500 kV AC transmission line to Central China Grid has a capacity of 12,000 MW. The other 500 kV DC transmission line HVDC Three Gorges-Guangdong to South China Grid has a capacity of 3,000 MW and supplies Guangdong.

Benefits from the Three Gorges Project

To China's leaders, the Three Gorges dam will provide a foundation for the nation’s future economic prosperity. The power will also help meet China's rapidly growing energy demand. Just as important, the transmission lines that are being developed to transport electricity from the project to the rest of the country will help to create a national grid, with the Three Gorges at its heart.

Transportation of people and goods will be greatly enhanced. The reservoir will allow 10,000-ton freighters to enter the nation's interior, which currently limits access to boats under 1,500 tons. Vessels will be able to navigate from Shanghai up to Chongqing, around 2000km from the sea. It could become an even more important transport artery if sufficient facilities are put in place to integrate cargo transport on the river with major rail and road intersections. The government and companies involved in the development of the Three Gorges dam are also keen to promote the project by developing it as a tourist attraction. Tour boats now offer trips on the reservoirs in order to allow foreign and domestic tourists to appreciate what are being advertised as ‘lofty gorges projecting peaceful lakes’.

 Wikipedia.Construction of the locks allowing Yangtze River shipping to bypass the Three Gorges Dam. Credit: Wikipedia.

The dam is also intended to provide major flood control benefits. Historically, the population in the middle and lower reaches of the Yangtze River suffered tremendous losses from flooding both in human lives and property. For example, the massive flooding of the Yangtze River in 1931 caused more than 3 million deaths from flooding and starvation.

The government also notes that the dam's power generation potential of 84.7BkWh/yr is the energy equivalent of burning 50 million tons of coal or 25 million tons of crude oil. Thus, the switch to cleaner hydroelectric power would have the effect of cutting 100 million tons of carbon dioxide, up to two million tons of sulfur dioxide, ten thousand tons of carbon monoxide, 370,000 tons of nitrogen oxide, and 150,000 tons of particulates annually from the atmosphere.

Social and Environmental Concerns

Critics of the Three Gorges project argue that the project’s costs may outweigh the benefits, the latter of which have allegedly been exaggerated by the government. The Three Gorges Dam project has become a symbol of national unity and strength for the ruling communist party. As a result, critics charge that many of the controversies surrounding the project are glossed over or ignored. In an address to the engineers of the dam, then Premier Li Peng, himself a power engineer by training, said the scale of the project was proof to the world of China's newfound strength. "The damming of the Yangtze is of great political and economic significance ... It proves to the whole world the Chinese people's capability of building the world's first-rate hydroelectric project". The construction of the dam has thus become as much a celebration of Chinese nationalism and its political leadership as it is a massive power and engineering feat.

Foreign perception of the project has suffered from the reputation of its principal proponent in Beijing, Li Peng. Li, whom some historians hold responsible for the 1989 massacre in Tiananmen Square, championed the idea of the dam to guarantee China's energy supply amid the internal political repression and international isolation that followed Tiananmen. Li was the driving force behind the approval of the project in 1992 by the National People’s Congress despite no votes or abstentions from a third of the delegates—a rare display of dissent in the Congress.

The relocation of local residents is a central part of the Three Gorges Dam Project. During the planning stages in the 1990s it was estimated that 1.13 million residents would be forced to relocate;  the final number was closer to 1.24 million after the relocation effort was completed in July 2008. This number represents about 1.5% of the total population of Hubei Province (60.3 million) and Chongqing City (31.44 million) where the reservoir is located.  About 140,000 residents were relocated out of Hubei province to eastern provinces and some central provinces, and the majority of the remaining people were relocated within Hubei Province. On October 11, 2007 Chinese state media announced that under a development plan of Chongqing city, an additional 4 million people will be encouraged to move from their homes near the dam to the Chongqing metropolitan area by the year 2020.

Critics claim that those forced out of the area have not been adequately compensated, particularly as the land they lost was highly fertile. But the government insists that the scale of its compensation package demonstrates its commitment to helping those affected improve their standard of living.

Behavioral scientists are studying the populations who will be forced to relocate because they live in a flooded area. Research suggests that anticipation of involuntary migration is a robust predictor of mental distress, and elevates depression) not only directly, but also indirectly by weakening the social and the psychological resources (i.e., social support and mastery), which safeguard the mental well-being of migrants

Upwards of 1,000 archeological sites will be submerged beneath the reservoir. Ancestral burial grounds and centuries-old temples, fossil remains, and archeological sites dating as far back as the Paleolithic Age risk being lost from public access and scholarly pursuit if they are not unearthed and relocated before the waters rise. The government has taken measures that it claims will mitigate these losses.

There is also concern about the impact the project will have on biological diversity. The baiji dolphin, the ancient river sturgeon and the finless porpoise depend on the Yangtze for their survival. The population of Siberian cranes in Poyang Lake will also be affected by the dam.

Sedimentation of the reservoir is also a serious challenge. The flow of the Yangtze carries with it the fifth-largest sediment discharge of any river in the world, equivalent to about 4 percent of all river-borne sediment discharged to all the oceans of the world. Sediment buildup behind the dam and throughout the reservoir would effect the overall storage capacity of the reservoir. The loss of storage capacity would directly result in a decrease in project’s flood control capability. The high rate of sediment deposit has already affected the diversion channel and is expected to compromise operation of the dam sooner and more seriously than had been anticipated.

The Yangtze River branches out into a broad estuary that stretches 655 kilometers into the East China Sea, and forms one of the largest continental shelves in the world. Over half of the Yangtze’s annual sediment load is deposited in the estuary. The health of the estuary depends on the delivery of this sediment because a significant relationship exists between intertidal wetland growth rate and riverine sediment supply. Yet, due to the Three Gorges project and other dams, the sediment accumulation rate in all reservoirs on the river has increased from close to zero in 1950 to more than 850 * 106 tons per year in 2003. This is causing erosion of the wetland habitat there, which provides nurseries for fish and resting areas for migratory birds and is considered one of the world's most important wetland ecosystems. A similar effect was seen on the Nile River after the Aswan Dam in Egypt was completed.



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