To dam or not to dam - the Yangtze.
To dam or not to dam
Done By: Wong Yun Sheng Calvin (1O/24)
Kock Kian Hong (1O/08)
Mai Yifan (1O/14)
Shih Yi-an (1O/18)
Benjamin Sing Wei Heng(1O/19)
A rough sketch of the Yangtze
What is the purpose of building the dam of such proportion? (refer to Appendix A)
This is to harness the energy of the Yangtze River. The resources for the production of energy from the Yangtze are enormous, although they have not been developed to a large extent. The total potential power is estimated to be more than 200 million kilowatts, representing about two-fifths of the total energy potential of all the rivers of China. The most ambitious project completed is the Ko-chou-pa hydroelectric dam above I-ch'ang, which is the first structure to block the flow of the Yangtze. The power potential in the vicinity of the Three Gorges is especially great, amounting to about one-fifth of the Yangtze's total potential. In the early 1990s preliminary work began on a massive dam and reservoir project there. Many tributaries of the Yangtze that have significant fall and volume-such as the Ya-lung, Min, and Chia-ling rivers-and other rivers that are tributaries of Lakes Tung-t'ing and P'o-yang also have considerable potential.
Briefly describe the magnitude of the project
Since construction began in 1993, almost 19.2 billion Yuan has been spent on it. 178 cubic metres of earth and stone have been removed over the past four years. This means that if a road one metre wide were paved with these stone and earth, it would stretch around the Earth at the Equator four and a half times. The dam will be 175 metres high and 2.5 km wide.
What are the potential benefits?
This is the largest engineering project in China and is expected to be completed in 2009. Upon its completion, it will be the largest dam in China and will generate as much hydroelectricity as 15 coal-burning power stations. The dam, which is also designed to span the Yangtze River just west of the city Yichang in Hubei, would also create an immense deep-water reservoir about 600km long that would allow ocean going 10000-ton freighters to navigate 2250km inland from the East China Sea to Chongqing. It would also control disastrous flooding along the Chang Jiang, facilitate inland trade and also provide much needed power for Central China.
What are the effects on the environment and the Chinese Society?
Once completed, the dam will flood 28000 hectares of crops and orchards and submerge 13 cities, 40 towns, 300 villages, and more than 1600 factories. As a result, mearly1.2 million people will have to be relocated. Of even greater loss would be the hundred or so historical sites that will be submerged if the dam is built, some dating back to 10000 BC. The dam will, however, control Yangtze's killer floods that have already displaced 38 million people, destroyed 5.6 million homes, and submerged 12,000 acres of crops. Also, it will allow vessels up to 10,000 tonnes to ...
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Once completed, the dam will flood 28000 hectares of crops and orchards and submerge 13 cities, 40 towns, 300 villages, and more than 1600 factories. As a result, mearly1.2 million people will have to be relocated. Of even greater loss would be the hundred or so historical sites that will be submerged if the dam is built, some dating back to 10000 BC. The dam will, however, control Yangtze's killer floods that have already displaced 38 million people, destroyed 5.6 million homes, and submerged 12,000 acres of crops. Also, it will allow vessels up to 10,000 tonnes to travel 1,500 km inland to Chongqing, opening up markets where 380 million people live. The dam will also create a huge number of jobs for the Chinese people
What reasons are there for discontinuing or supporting the project? (refer to Appendix D)
Discontinuing
The reservoir formed will destroy important archaeological sites. There will also be permanent damage to the spawning grounds of many fish, such as the white dolphin and the Chinese alligator. The silt-free river downstream of the dam will cause rapid erosion of the river's banks and may thus cause huge landslides. Flooding of the valley behind the dam will displace 1.2 million people. 13 cities, 140 towns and 4000 villages will disappear beneath the reservoir and will have to be rebuilt on higher ground. 500 million tonnes of sediment will accumulate behind the dam every year. This will deprive farming areas downstream of silt, which is a natural fertiliser. The dam will also be the first target in the war, and if it is destroyed, not only will all the money and time spent on it go to waste, the whole of Central China will also be flooded. The first early River-Valley Civilizations developed in the Yangtze River. Many Chinese dynasties had developed their great civilization along this river, especially near the three gorges. As a result, a lot of ancient buildings and other kinds of relics were left alongside the river. The building of the dam will destroy these archaeological relics.
Continuing
It will facilitate inland trade by allowing 10000-ton freighters to navigate inland from the South China Sea. The hydroelectric power produced by the dam is equal to burning 40 million tons of coal in thermal power stations. Coal-fired power stations pollute the atmosphere and contribute to acid rain and global warming. The dam will regulate the flow of the Yangtze River. During the 20th century 300,000 people died from flooding in the Yangtze Valley. By eliminating rapids, the dam will improve navigation on the Yangtze. By regulating the flow of the Yangtze, more water should be available for irrigation. Thousands of jobs will be created: builders, engineers, transport jobs, trade jobs, electricians, service jobs in towns, town planners etc.
A short reflection on the issue
The construction of the Three Gorges Dam has both advantages and disadvantages. As an advantage, the project will help to control the disastrous floods of the Yangtze. It will also produce enormous amounts of hydroelectric power for Central China and at the same time, reduce the amount of coal that is used to generate electric power, which would cause environmental pollution. It will also facilitate inland trade. However, the dam construction has also caused many disasters. It destroys many archaeological finds and China has lost cultural relics that are very valuable and meaningful for historians and archaeologists. Many fish species will not be able to survive in the river because the water temperature is now below 64 degrees Fahrenheit and water pollution has been increased. Also, it causes more than 1.2 million people to move away. Many of them also lose their property. However, the compensation that the people get is far less than what they have lost during the resettlement. There has also been an increasing amount of corruption because of this, with many officials pocketing money that was meant as compensation for the people. The Three Gorge Dam may become the major target to the enemy if China is involved in a war. However, if China promotes diplomacy, the dam will never be a major target to any nations. The construction causes water pollution, but it is just temporary. Hydroelectricity produced by the dam is a clean substitute for coal. Flooding in the Yangtze causes deaths; the destruction of buildings and crops, and economical lost. China should also try its best to save the cultural relics in the Yangtze. It seems that the Chinese government has had to give up many things in order to complete this project. It does not seem as though the Chinese government has gained more benefits than what it has lost.
However, since the dam construction is underway, it is very unworthy if the government discontinues it. While China continues constructing the dams, she should find a way to stop corruption, and also provide a better resettlement plan for the local residents. After the construction has been completed, the Chinese government may consider the continuation of compensation for resettlers who are unable to make a living.
Appendix A
Why do People build dams?
Its purposes are to meet demands for water for human consumption, irrigation, or industry; to reduce peak discharge of floodwater; to increase available water stored for generating hydroelectric power; or to increase the depth of water in a river so as to improve navigation. An incidental purpose can be to provide a lake for recreation.
Appendix B
How do Engineers go about building dams?
Investigation of a site for a dam includes sinking trial borings to determine the strata. The borings are supplemented by shafts and tunnels which, because of their cost, must be used as sparingly as possible. In the shafts and tunnels, tests can be made to measure strength, elasticity, permeability, and prevailing stresses in strata, with particular attention given to the properties of thin partings, or walls, between the more massive beds. The presence in groundwater of chemical solutions harmful to the materials to be used in the construction of the dam must be assessed. Sources of construction materials need exploration. As dams continue to increase in height, the study of foundation conditions becomes increasingly critical.
Model tests play a major part in the structural, seismic, and hydraulic design of dams. Structural models are particularly useful in analysis of arch dams and in verifying analytical stress calculations. Various materials have been used for model tests; on some early tests for Hoover Dam, rubber was employed. The need for accurate reproduction of stress patterns in complex models is met by using material of low elasticity. In a sense, dams themselves are models for future design. The instruments built into them to record movements under load, strains within materials after construction, temperature and pressure changes, and other factors are installed primarily to study the performance of the structure and to warn of possible emergencies, but their value in confirming design assumptions is important.
Appendix C
What kinds of materials are needed?
Most dams are of two basic types: masonry (where concrete is used) or embankment (where earth or rock fill is used).
Appendix D
What are some of the advantages and disadvantages of building dams?
Advantages: They can provide a healthy and inexhaustible source or hydroelectricity. It can also reduce flooding in a particular area. They can also improve inland trade by deepening the depth of a river. They can also provide a source of water for human consumption, irrigation or industrial purposes (e.g. Hoover Dam in Arizona). The lake behind the dam may also be transformed into a recreation area.
Disadvantages: Serious consequences follow if a dam is overtopped. Disaster is likely in the case of an embankment dam not designed to permit uncontrolled flow of water on its downstream slope. In March 1960 the partially completed embankment dam at Oros, Brazil, was accidentally overtopped during a period of unexpectedly heavy rainfall. Despite heroic efforts to avert disaster, the water level rose nearly three feet above crest level, eroded about half the fill in the dam, and cut a deep breach about 660 feet wide in the structure. Although there was time to evacuate 100,000 people living downstream, half were subsequently rendered homeless and about 50 perished. Dams can also prevent fish from migrating, such as adult salmon when they move upstream, and young salmon from reaching feeding grounds. Sediment in rivers seriously influences the effective life of a reservoir and therefore the financing of a dam. Some modern dams have been rendered useless for storing water because the reservoir has filled with silt.
Sources
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