Three gorges dam; a wonderful landmark of civil constructionArticles > Three gorges dam; a wonderful landmark of civil construction
Three Gorges Dam China:
Three-Gorges-Dam is a huge hydroelectric dam that’s reservoir extends through the Yangtze River across the town of Sandouping, Yiling County, Hubei Province, central China, downstream of the Three Gorges River. Three-Gorges-Dam has been the world's largest power station in terms of installed capacity (22,500 MW) since 2012. In 2018, the dam produced 101.6 terawatt-hours (TWh), breaking its previous record, but still slightly lower than Itaipú Dam, which made world record in 2016 after producing -103.1 TWh.
The structure of the dam was completed in 2006. The power station project dam was completed and fully operational from July 4, 2012, when the last major hydroelectric power plants in underground plants began production. Each large water turbine has a capacity of 700 MW. Six hydroelectric power plants and two small generators (50 MW each) are combined to generate the power from the plant itself, with a total capacity of 22,500 MW. The final phase of the project, lifting the ship, was completed in December 2015.
Apart from the electric generation, the dam is intended to increase the shipping capacity of the Yangtze River. By providing a repository for floodplains, the dam reduces the potential for flooding below the river that could affect millions. China considers the project to be a major social and economic achievement, with the design of large-scale turbines, and a reduction in emissions. However, the dam is flooded with archeological and cultural sites, leaving some 1.3 million people homeless, and has created major environmental changes including increased risk of landslides. As a result the dam was controversial both internally and internationally.
Construction Material of the Three-Gorges-Dam:
The dam is composed of a straight-crested concrete gravity structure. The Three-Gorges-Dam is 2553.587 yards (7,660 feet) long with a height of 202.318 yards (607 feet). It incorporates 28.00 million cubic metres (37.00 million cubic yards) of concrete and 463,000.00 metric tons of steel/metal into its design. Submerging large areas of the Qutang, Wu, and Xiling gorges for some 600.00 km (375.00 miles) upstream, the dam has created an immense deep-water reservoir allowing ocean-going sailors to navigate 2,250.00 km (1,400.00 miles) inland from Shanghai on the East-China-Sea to the inland city of Chongqing. Limited hydroelectric power production began in 2003 AD, and gradually increased as additional turbine generators came online over the years until 2012 AD, when all of the dam’s 32 turbine generator units were operating at a time. The units, along with 2 additional generators, increased the capacity of the dam to generate 22,500 megawatts of electricity, thus, making it the most productive hydroelectric dam of the world. An other purposed of the construction of the dam was also to prevent millions of people from flood, which they had faced each year, before the its construction.
Constructional History of the Dam:
The construction plan of the dam was first discussed in the 1920s by Chinese Nationalist Party leaders. The idea of ??the Three-Gorges-Dam was given new impetus in 1953, when a Chinese leader Mao Zedong ordered a study of the possibility of multiple sites for the construction of dam. Detailed planning of the project began after 1955. Severe criticism of the Three-Gorges-Dam project began shortly after plans were proposed and continued with its construction. Significant problems including the risk of the dam collapsing, the migration of an estimated 1.3 million people (critics assert that the figure was actually 1.9 million) living in more than 1,500 cities, towns and villages, and the destruction of the most beautiful and unusual land for construction and archeology. There were also fears - some of which were proven - that human and industrial waste from cities would pollute the lake and that too much water trapped in the lake could cause earthquakes and landslides. Some Chinese and foreign engineers say that many smaller and cheaper and less problematic dams on the Yangtze rivers could produce as much energy as the Third Gorge Dam and control floods equally. The construction of these dams, they said, would enable the government to achieve the most important without risk.
Because of these problems, the operation of the three Gorges Dam was delayed for almost 40 years as the Chinese government struggled to reach a decision to continue with the project plans. In 1992 Prime Minister Li Peng, who also trained as an engineer, finally persuaded the National People's Congress to confirm the decision to build the dam, even though about a third of its members refused or voted for the project - an unprecedented sign of resistance from the body. President Jiang Zemin did not support Li when the dam officially opened in 1994, and the World Bank refused to transfer Chinese funds to support the project, citing major environmental problems and more.
Nevertheless, the Three Gorges project went ahead. In 1993 work on the highways was introduced in the area. Workers blocked and diverted the river in 1997, closing the first phase of construction. In 2003 the dam began to overflow, the ship's locks - which allowed up to 10,000 tons to pass through the dam - became operational, and the first dam's electricity was connected to the grid, completing the second phase of construction. (After the completion of this second phase, some 1,200 historic and archaeological sites that once reached the Yangtze River in the middle of the river disappeared when the floodwaters rose.) The construction of a large dam wall was completed in 2006. The rest of the dam's generators were operational by mid-2012, and the lifeboat, which allowed up to 3,000 tons of vessels to pass through millions of vessels and quickly passed through the dam, became operational in late 2015
Environmental Impacts of the dam:
According to China's National Development and Reform Commission, 366 grams of coal will produce 1 kWh of electricity by 2006. From 2003 to 2007, energy production from water equaled 84 million tons of ordinary coal.
(1). Soil erosion and sediment fall:
Two dangers are specifically identified in the dam. One is that there is no consensus on sediments, and the other is that the dam is based on earthquake fault. At present levels, 80% of the land area in the total area of dam is experiencing erosion, which puts about 40 million tons of sediment at Yangtze each year. Because of the slow flow above the dam, most of the sewage will now be blocked there instead of flowing downstream.
- Shanghai, more than 1,600 km (990 mi) away, rests on a massive sedimentary plain. The "arriving silt—so long as it does arrive—strengthens the bed on which Shanghai is built... the less the tonnage of arriving sediment the more vulnerable is this biggest of Chinese cities to inundation.
- Benthic sediment buildup causes biological damage and reduces aquatic biodiversity.
- Some hydrologists expect downstream riverbanks to become more vulnerable to flooding.
(2). Risk of Land-sliding:
Erosion in the dam-reservoir, caused by rising water, causes alarming land-sliding that has led to significant disturbance in the dam-reservoir. It includes two incidents in May 2009 when somewhere between 20,000 and 50,000 cubic meters (26,000 and 65,000 cubic yard) flooded the Wuxia River flooded -Wu River. Also, in the first four months of 2010, there were 97 major landslides, which brought enormous disturbance in the reservoir.
(3). Waste management:
The dam managed an advanced upstream wastewater treatment around Chongqing and its suburbs. According to the Ministry of Environmental Protection of China, as of April 2007, more than 50 new plants could treat 1.84 million tonnes per day, 65% of the total need. About 32 landfills were added, which could handle 7,664.5 tonnes of solid waste every day. Over one billion tons of wastewater are released annually into the river, which was more likely to be swept away before the reservoir was created. This has left the water looking stagnant, polluted and murky.
In 1997, the Three Gorges area had 10% forestry, declining from 20% in the 1950s. A study by the United Nations Food and Agriculture Organization suggested that the Asia-Pacific region acquired approximately 6,000 km2 (2,300 sq mi) of forest land in 2008. That is a major change from a total net loss of 13,000 km2 (5,000 sq mi). forestry every year in the 1990s. This is due to China's massive reforestation efforts. This came soon after the 1998 Yangtze River floods convinced the government to restore tree cover, especially in the Yangtze valley north of Gorges Dam.
(5). Risk to Wildlife:
Concerns about the potential impact of the dam on wildlife preceded from the 1992 National People's Congress. This region has long been known for its rich biodiversity. It is home to 6,388 plant species, belonging to 238 families and 1508 subspecies. Of these plant species, 57 percent are endangered. These rare species are also used as ingredients in traditional Chinese medicine. Currently, the percentage of forested area in the region around the Third Gorges Dam has dropped from 20 percent in 1950 to less than 10 percent since 2002, severely affecting all plant species in the area. The region also provides habitats for hundreds of species of freshwater and terrestrial species. Freshwater fish are particularly affected by dams due to changes in water temperature and water flow. Many other fish are also injured in the turbine blades of the power plants. This is particularly damaging to the region's environment because the Yangtze River basin is home to 361 species of fish and contains 27 percent of all endangered freshwater fish species in China. Some aquatic species are endangered by the dam, particularly the baiji fish, or dolphin of the Chinese river, which is getting extinct. In fact, Chinese government officials have even suggested that the Three-gorges-Dam directly caused the extinction of the baiji fish. Chinese paddlefish are also believed to be partially extinct due to the dam blocking their migration.
Of the 3,000 to 4,000 left in Siberia's most endangered region, a large number are currently spending the winter in wetlands to be destroyed by the Third Gorges Dam. The dam contributed to the effective extinction of the baiji Yangtze river dolphin. Although it was close to this level even at the beginning of construction, the dam continued to reduce its habitat and increase navigation, which was one of the reasons for its demise. In addition, the population of Yangtze sturgeon is guaranteed to be "badly affected" at the dam.
(6). Three gorges dam; a risk for the earth:
In 2010, NASA scientists calculated that the change in the level of water stored in dams would increase the Earth's duration of the day by 0.06 microseconds and cause the earth’s polar regions slightly extend and the equatorial region flatten. The flattening of equatorial region and protruding of the polar region will convert the spherical shape of the earth into quite round shape. The spherical shape of earth brings change in weather during the year. If the earth will round, the change in the weathers will be very slighty.
Structural Integrity of Three Gorges Dam:
A few days after the initial completion of the dam, 80 hairline-cracks were seen in the dam structure. However, 163,000 concrete units of the Three Gorges Dam all passed quality testing and distortions were within design limits. The team of experts gave the project a high level of quality.German water engineer Wang Weiluo, who has been critical of the Three Gorges Dam project for years, says financial abuse by government officials related to rushing construction work has led to structural deficiencies that could lead to the dam failing to leak foundation.
In 2019, images on Google Earth, where the appearance of the images showed a significant decline in the structure, led to rumors on social media of a possible collapse of the dam. Chinese authorities have dismissed the allegations and re-examined previous dam inspections. The rumors resurfaced in 2020, and a Chinese waterologist based in Germany warned of an impending fall. On July 18, 2020, China's official Xinhua News Agency reported that "Three Gorges Project's operational monitoring records show that values ??between key parameters such as dams relocation, low-level paperwork, and flexibility were within normal range, and safety building standards. The water in the dam was stable ”. Chinese media reported on the relocation, expansion of paperwork, and the conversion of the Three Gorges dam. In a report on July 21, 2020, the Global Times criticized western media reports for reporting on their Three Gorge Dam report, accusing them of interfering, casting their reports out of context, and lacking "basic knowledge of physics". The report explained that the term, "deformation" should have been a common engineering concept, and it never stated that their dam had failed structurally.
Steps taken for prevention of soil erosion downstream:
To increase the use of Three Gorge Dam and to reduce sediment deposition in the reservoir of the dam eroding from the Jinsha River, above the Yangtze River, authorities are planning to build a series of Jinsha dams, including Wudongde Dam, Baihetan Dam, and the Xiluodu and Xiangjiaba dams that have now been completed. The total capacity of the four dams is 38,500 MW, almost double the capacity of the three Gorges. Bahaihetan is being built and Wudongde is seeking government approval. The other eight dams are in the middle of Jinsha and the other eight upstream. The upstream dams will reduce the flow of silt and sediment to deposit in the reservoir of the Three-gorges Dam, thus improving its utility.
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