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Case Study: Three Gorges Dam, China Review |
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Three Gorges Dam, China - A Review Large (or mega-) dams (over 100 m high) have been widely used for flood protection and water resource management. The construction of the colossal Hoover Dam in the 1930s heralded the start of an economic and political craze, particularly during the 1950s and 60s, for large dams, which continues to the present day. They were believed to be the solution to water supply or flood problems, or as a 'green' source of power. However, the environmental (and in some cases economic) problems soon became apparent and fluvial geomorphologists and some dam engineers have switched to constructing strategically placed small dams. However, some countries and dam engineers have failed to heed these lessons and have continued to pursue the construction of mega-dams. The most topical and controversial large dam scheme is undoubtedly the Three Gorges Dam on the Yangtze River, China. It will be the largest man-made structure in the world. It has been constructed not only for flood protection, navigation and hydroelectric power generation purposes, but as a political statement to the world. The impact on the local populations has been immense, involving relocation of over a million people, the abandonment (and eventual inundation under dam waters) of entire cities, the drowning of archaeological sites, and destruction of the wildlife and habitats during construction. The Three Gorges Dam will be the largest and most expensive dam ever constructed along the Yangtze. The Three Gorges refers to towering limestone cliffs of the the Qutang, Wu and Xiling gorges, which stretch for about 200 km from Fengjie (Sichun province) to Yichang (Hubei province) along the middle reaches of the Yangtze (Internet 1; Sutton, 2004). Along with the Yellow River in the north, the Yangtze is of fundamental importance to the culture and psyche of the Chinese as well as the economic well-being of the country. At 6 300 km long, the Yangtze (Chang Yiang, meaning Long River) ranks as the third largest in the world and the largest in China. More than 700 tributaries drain 1.8 million km2 (Internet 2), approximately 20% of China's land. The river drains from the Tibetan Plateau in the east, flows through China's largest and heavily polluted city, Chongqing, and enters the sea in the west near Shanghai. The catchment of the Yangtze represents 25% of entire crop land, 350 million people (33% of China's population), 40% of grain, 70% of rice, 40% of agricultural and industrial output (Internet 2) in China. The idea of a giant dam on the Yangtze at the Three Gorges was first proposed in 1919 by Dr Sun Yet-Sen, founder of the first Chinese republic. After floods in the 1930s killed 200 000 people, the area was surveyed with engineers from the US Bureau of Reclamation. Following 30,000 deaths as a result of floods in 1954, the new Communist ruler Mao Tse Tung was attracted to Soviet proposals for the Three Gorges (Pearce, 1992). Mao swam in the Yangtze in 1956 and wrote a poem 'The Lake Among the Gorges'. He wrote: "Great plans are afoot. The mountain goddess, if she is still there, will marvel at a world so changed." During the late 1950s under the direction of the Yangtze Valley Planning Office, 10 000 technicians were involved in planning, but after 1960 it was dropped in favour of other irrigation and drainage projects (Pearce, 1992). Over the next three decades of turbulent politics the project fell in-and-out of favour. Strong citizen opposition, and scientific and media objections, also forced the People's Congress to suspend plans. However, the ascent of Premier Li Peng and the Communist clampdown, particularly in the aftermath of the massacre at Tiananmen Square in 1989, led to the project going ahead (Internet 3) and construction commenced in 1994. The Gezhouba Dam upstream was initiated as a trial run for the project (Internet 4). When completed, the Three Gorges Dam will be the largest, most expensive dam and the largest hydroelectric power plant ever constructed, generating eight times more power than the High Aswan Dam (Pearce, 1992). The Three Gorges Dam Project will involve a 185 m (600 feet) dam containing a reservoir 632 km (375 miles) long, 1100 m (3,600 feet) wide, maximum depth of 175 m (575 feet), approximately 39.3 billion m3 of water and inundating 30,000 hectares of arable land. 19 cities and 326 towns will also be drowned. In October 1997 a diversion canal was open for navigation and the following month the main channel was dammed (Internet 4). It will take 18 years to build, and it is due for completion by 2009 AD and fully operational in 2013 AD (Internet 2). Many international funders (e.g. World Bank and the US Export-Import Bank) and construction firms (e.g. US Bureau of Reclamation, Bechtel Enterprises, BC Hydro and Ontario Hydro) have refused to participate in the project (Internet 2) boycotting because of the economic and environmental controversy surrounding the project. Foreign financing has come from strong-export credit agencies, which are not restricted by environmental or human rights regulations (unlike development agencies such as the World Bank), in Canada, Germany, Switzerland and Japan (Internet 2). The projected cost is US$10.7 billion (Internet 2), but opponents claim that total costs (including the dam, new housing, infrastructure, etc.) could amount to US$ 75 billion (Zich 1997). 3. Benefits3.1 Flood controlSeasonal flooding is a serious problem along lower Yangtze, occurring approximately every 5 years. During the past 2,000 years since the Han Dynasty, 214 flood disasters recorded along Yangtze, 11 of them in the last 70 years (Internet 2). The 1870 flood, considered the largest for 4 000 years, drowned 240 000 people and 1 million hectares of land (Internet 2). During the 1931 flood, 140,000 people were killed (Internet 4); 30,000 were killed and 1 million made homeless during the 1954 flood (Internet 2), and in 1996 2,700 people were killed. Present flood defences along the Yangtze include dykes up to 16 m high and flood basins, which act as a safety valve. However, these dykes are in constant need of maintenance. At the height of the 1991 flood 1 million people were involved in reinforcing the dykes to prevent breaches (Pearce, 1992). 3.2 Power generation Coal provides 66% of China's energy, burning 1.1-1.2 billion tons of coal per annum and emitting vast volumes of carbon dioxide (Internet 2). Continued industrial growth and growing energy demands will increase this figure. The future Sanxia hydropower station will be largest in the world and reduce China's dependance on coal. 26 turbines, each possibly 400 tons each, will generate 18 200 MW (50% more than the Itaipú Dam, Paraguay, the world's present biggest) (Zich, 1997). This will be equivalent to the output of 178 nuclear power plants, or the burning of 40-50 million tons of coal per year (Internet 2) or 25 million tons of crude oil per year (Internet 4). This will drastically reduce carbon dioxide and sulphur emissions and so limiting future increases in greenhouse effect and acid rain. In contrast, virtually pollution-free HEP seems an attractive proposition. Present navigation is hindered by dangerous shoals of sediment and rapids. The reservoir will submerge shoals, deepen the channel, have more gradual banks and slower flow. At the dam, two five-stage locks will raise deep-draft ships (up to 10,000 tons), whilst a ship lift will service smaller vessels (up to 3,000 tons) (Zich, 1997). This will improve passage and increase shipping volumes between Yichang and the major industrial city of Chongquing (population 15 million). Chongquing will become accessible to ocean-going vessels (Internet 4) of up to of 10,000 tons (ten times the normal capacity) (Internet 2; Zich 1997). 3.4 Economic growth and development Hydro-electric power will allow for industrial growth and supply power to Eastern and Central China and Eastern Sichaun. Concomitant with the dam, construction of new towns and infrastructure are generating employment. At present, 60,000 workers are employed at the dam site. Construction of the dam in Central China is of strategic importance. Destruction would be disastrous both militarily and for nation (Internet 2). 3.5 Water supply It is envisaged that the dam will supply Shanghai's 13 million inhabitants with water (and other cities). 4. Detrimental effects4.1 Environmental impactsThe environmental impacts as a consequence of the construction of large dams is well documented in the scientific literature. The greatest effects will be on the patterns of erosion and deposition in the river, the unnatural flow regime downstream of the dam, and water quality and temperature will affect ecosystems downstream. 4.2 Sedimentation It is envisaged that the dam will sediment loads along Yangtze are very high. Sedimentation behind the dam will be a serious problem. The dam may trap 70% of bedload behind the dam, thereby continually losing storage capacity. Possible silting-up of Chongqing's deep-draft harbour (Zich, 1997) may also obstruct navigation. Silting may also impede the generation of electricity Erosion of bed and banks downstream, and channel lowering (degradation, is expected to occur for hundreds of kilometres downstream, eroding flood control embankments, undermining bridge supports, changing hydrological regime of the river (Internet 2). The effects may be felt as far downstream as the mouth of the Yangtze - the delta may become eroded due to reduction in sediment (Internet 4). Although accommodating smaller flood events, it is argued that dam will not be able to contain largest floods, and so flood hazard will remain a problem downstream. 4.3 Aquatic and terrestrial ecosystems Dams reduce downstream water temperature and downstream water levels may be artificially raised at certain times of year. Most fish sensitive to water temperature and stage especially for breeding which may result in reductions or elimination of native species. The flooding of gorge to produce reservoir will drown habitats. Presently endangered species include Chinese Sturgeon and paddlefish, Yangtze dolphin, Chinese tiger, Chinese alligator, Giant Panda, and Siberian Crane will come under greater stress. 4.4 Water pollution and diseaseThe Yangtze River is presently the biggest sewer in China. Pollutants from thousands of industrial plants and mining (including heavy metals such as arsenic, cyanide and methylmercury), agricultural runoff, residential wastewater, urban sewers, pollution from shipping (Internet 2) enter the river. Obstructing river flow and slowing water will concentrate toxins and pollutants, which otherwise would have been washed downstream and out to sea. Furthermore, the cessation of annual flooding and deposition of fertile silt onto fields, resulting in increased use of chemical fertilisers and resulting associated problems of nitrate runoff and groundwater pollution. Displaced people likely to suffer epidemics of infectious diseases (Anderson, 1999), in particular schistosmiasis (disease caused by tiny blood flukes that can damage liver and intestines). Over the past 5 years infection has dropped by 50% as a result of treatment with the drug praziquantel, but the changed cycle of flows downstream of dam may increase the number of water snails carrying the flukes. Infected snails are presently found 500 km above the dam, but previously could not transverse the rapids (Anderson 1999). In addition, ambient temperatures above the reservoir are expected to be 1oC warmer allowing mosquitoes carrying Japanese B encaphalitis and malaria to proliferate (Anderson, 1999). Also as terrestrial animals seek higher ground to escape the flooding of the reservoir pest levels will be increased in surrounding towns and cities (Internet 2). 4.5 Landslides Loading of the dam structure and reservoir water on the Earth's crust may place generate further crustal stresses in an area already prone to small earthquakes. In 1958 a large landslide near the site generated a flood wave tens of metres high (Pearce, 1992). Overtopping of the dam or dam breach could submerge towns and cities such as Wuhan. 5. Social impacts5.1 ResettlementEntire towns and cities (such as Wushan at the confluence of the Yangtze and Daning River) will be submerged under the waters of the reservoir (Sutton, 2004). The Yangtze River Water Resources Commission will relocate 1.2 million people, provide new farmland for 300 000 farmers (Internet 2). Forced resettlement, which started in 1995 with the first-wave moved in 1997, will span over 20 years (Internet 4). 13 new towns and cities (such as Zigui which will accommodate 30,000 inhabitants) are being constructed on higher ground (Zich 1997) to replace towns such as Wanzian which presently have 140 000 people (Pearce, 1992). Historically, many people ousted from their homes by dams projects elsewhere still live in abject poverty (Pearce, 1992). Relocation will affect traditions, lifestyles and cultures. The region has been inhabited since Palaeolithic and has accumulated a wealth of archaeological sites remain. Although some, such as Zhang Fei Temple at Yungang, will be relocated (Zich, 1997), 800 sites of cultural relics will be destroyed (Internet 2). This will affect the tourism to the area. 5.3 Economic impacts Industry will be displaced and, although new industries will be attracted, costs will be high. 5.4 Agriculture 14 500 hectares of agricultural land will be inundated. Compensation will be needed farmers. Increased output will be required from other land, but farming on higher ground may have less fertility and thinner soils. There will also be loss of fertile sediment previously deposited on floodplain downstream during annual floods. Farming near estuary will be affected by lower flows and intrusion of salt water around Shanghai (Internet 2). 5.5 FisheriesConsequences include change of habitats, a general transformation from rapid to slow moving waters and reduction in sediment, and soils being deprived replenishment of nutrients from sediments. Commercial fisheries will be affected (black, silver, grass and variegated carp breed) and fish are often killed in electric turbines of dams (Internet 2). 6. OverviewThe Three Gorges Dam project not only allows the Chinese people to harness the river’s power and tame its destructive force, but it is a political statement by the Chinese government. Opponents to the project would like to see smaller scale hydroelectric power (HEP) projects situated on the tributaries of the Yangtze, to move industry westwards nearer to the hydro-electric power sites, and to increase the presently wasteful energy consumption of industry (Pearce, 1992). 6.1 Engineering concernsThere are questions over whether such a large dam can be constructed safely. There is tear of dam failure and the threat of sabotage. Panic to 350 million people downstream of the dam. If the reservoir was emptied to neutralise, power generation would be lost (Pearce, 1992). A military expert is quoted in Qing (1994) as describing it as "a Sword of Damocles that will hang over the heads of future generations" (Pearce, 1992). 6.2 Human rights issuesAlthough domestic opposition has been muted since the Tiananmen Square incident. International opposition continues (e.g. Probe International, a Canadian environmental group) (Internet 4), journalist Dai Qing was imprisoned for ten months for published a critical book titled Yangtze! Yangtze! (Zich, 1997). 6.3 Terrorist and military attacksSuch a project would be a prime target for a major terrorist attack. Although sited well within Chinese boundaries, it is also a major military target. See Worksheet 3 section for an outline of the major players in this issue. 6.5 The Wider Context: The Big Dam DebateSee the discussion on the Synopsis page. 7. Bibliography
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© British Society for Geomorphology (Education and Outreach). Author: Dave Simm, Bath Spa University College (2004). |
