The Three Gorges Dam is a hydroelectric river dam that spans the Yangtze River in Sandouping, Yichang, Hubei, China. The total electric generating capacity of the dam will reach 22,500 megawatts,at which point it will be the largest hydro-electric power station in the world. This is the biggest project that has been undertaken in China since the Great Wall and the Grand Canal. Several generators are yet to be installed; the dam is not expected to become fully operational until about 2011.

As with many dams, there is a debate over costs and benefits. Although there are potential economic benefits such as flood control and hydroelectric power, there are also concerns about the relocation of people who have been or will be displaced by the rising waters; siltation that could limit the dam's useful life; loss of numerous valuable archaeological and cultural sites; and the adverse effects of increased pollution upon the regional ecosystem.

Project history

The dam was originally envisioned by Sun Yat-sen in The International Development of China in 1919.In 1932 the Nationalist government, led by Chiang Kai-shek, begins preliminary work on plans for a dam in the Three Gorges. Then in 1939 the Japanese military forces occupied Yichang and surveyed the Three Gorges. A design, the Otani plan, was completed for the dam. Japan intended to build after its anticipated victory over China. In 1944 involvement from the United States began when the Bureau of Reclamation engineer J.L. Savage surveyed the area and drew up a dam proposal. Around 54 Chinese engineers were sent to the U.S. for training. Some exploration, survey, economic study, and design work was done, but the government, in the midst of the Chinese Civil War, halted work in 1947.

After the 1949 communist victory, the leader Mao Zedong supported the project, but the Gezhouba Dam project was begun first and economic problems including The Great Leap Forward and the Cultural Revolution slowed progress. In 1958, after the Hundred Flowers Campaign, some engineers who spoke out against the project were imprisoned.

During the 1980s plans were revived. Pushed through by Li Peng, the dam was approved by the National People's Congress in 1992 with a record number of abstentions and dissenting votes. The construction started on December 14, 1994.[8] The dam was expected to be fully operational in 2009, but due to additional projects such as the underground power plant with 6 additional generators, and due to the complexity of the ship lift, the dam is not expected to become fully operational until about 2011.

Scale of the project

The dam wall is made of concrete and is about 2,309 metres (7,575 ft) long, and 101 metres (331 ft) high. The wall is 115 metres (377.3 ft) thick on the bottom and 40 metres (131.2 ft) thick on top. The project used 27,200,000 cubic metres (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 metres (134,200,000 cu yd) of earth.

When the water level is maximum at 175 metres (574 ft) over sea level (91 metres (299 ft) above river level) , the reservoir created by the Three Gorges Dam is about 660 kilometres (410 mi) in length and 1.12 kilometres (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 sq km. The reservoir will flood a total area of 632 sq km of land compared to the 1,350 sq km of reservoir created by the Itaipu Dam. The Three Gorges Dam reservoir is longer than the 560 kilometres (348 mi) length of Lake Superior, but only 1.1 % of the surface area of the lake (82,400 sq km) 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 maximium water level (175m above sea level) by the end of 2008.

Economics

Three Gorges Dam Francis Turbine

When finished, the project will have cost 180 billion yuan, over 20 billion yuan less than the initial estimated budget of 203.9 billion yuan, just under 30 billion USD. This is because the calculation accounts for the effect of inflation, and the lower costs are attributed to a low inflation rate in recent years. It is estimated that the cost of construction will be recovered when the dam generates 1000 TWh of the electricity, which will be sold at the price of 250 billion yuan. This will take 10 more years after the dam starts full operation.

Sources for funding include the Three Gorges Dam Construction Fund, revenue from Gezhouba Dam, policy loans from the China Development Bank, loans from domestic and foreign commercial banks, corporate bonds, and revenue from Three Gorges Dam before and after it is fully operational, with additional charges for electricity contributing to the Three Gorges Construction Fund. The additional charges are as follows: Every province receiving power from the Three Gorges Dam has to pay an additional charge of ¥7.00 per MWh. Provinces that will not receive power from the Three Gorges Dam have to pay an additional charge of ¥4.00 per MWh. Tibet does not have to pay any additional money.

The Three Gorges Dam is the world¡¯s largest hydro-electric power station by total capacity, which will be 22,500 MW.It will have 34 generators in total. 32 of them are main generators, each with a capacity of 700 MW, and the other two are plant power generators to power other 32 generators, each with capacity of 50 MW. Fourteen are installed in the north side of the dam, twelve in the south side and the remaining six in the underground power plant in the mountain south of the dam. After completion, the expected annual electricity generation would be over 100 TWh, 18% more than originally predicted 84.7 TWh, since six more generators were added to the project in 2002.

Generators

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 installs Francis Turbines. The Francis Turbine is the most efficient turbine in the world. The diameter of the turbine is 9.709/10.427m(VGS design/Alstom's design). It rotates at a speed of 75 rpm. The normal rated power of the generator is 778 MVA. The maximum power is 840 MVA. The power factor is 0.9. The generator produces electrical power at 20 kV. The outer diameter of the generator stator is 21.42/20.9m. The inner diameter is 18.5/18.8m. The height of the stator is 3.13/2.95m. It is the biggest stator in the world. The load at the bearing is 5050/5500 tonnes. The efficiency of the generator is above 90%.

The generators are manufactured by two joint ventures. One of them includes Alstom , ABB , Kvaerner and the Chinese company Haerbin Motor. The other includes Voith , General Electric, Siemens (abbreviated as VGS), and the Chinese company Oriental Motor. The technology transfer agreement was signed together with the contract. More than 8 of the 32 generators are made in China. Most of the generators are water-cooled. Some newer ones are air-cooled, which are simpler in design,manufacture and easier to maintain.

Generator installation progress

The 14 generators in north side of the dam have already been installed. The first one (No.2 ) started to power on July 10, 2003. The last one (No.9) started to power on September 7, 2005. All the 14 generators first ran to full power (9800 MW) on October 18, 2006 after the water level had been raised to 156 m.

The first generator (No. 22) in the south side of the dam started working on June 11, 2007. Four generators on the south side of the dam are currently being installed, with another 8 already completed. The sixth generator in the south side (No. 17) started working on December 18, 2007. It brought the total capacity of the dam to 14.1 GW, surpassing the generating capacity of Itaipu (14.0 GW), to become the largest hydroelectric power plant in the world. The seventh generator in the south side (No. 17) started working on December 27, 2007.The eighth generator in the south side (No. 24) started working on April 25, 2008.]The total capacity of the plant is currently at 15.50 GW. The underground power plant and its six generators are still under construction. The Three Gorges Dam project also sets the record of having most generators being installed in one year (2007), that is 7 units with a capacity of more than 5000 MW.

Total power generated

As of 12:00 am May 9, 2008 the Three Gorge Dam Project had generated over 223 TWh of electricity, more than one fifth of the 1000 TWh it needs to generate to cover the cost (see Economics section)

Power distribution

The electricity generated by the Three Gorges Dam project is sold to the State Grid Corporation and China South Power Grid Corporation at a rate of ¥250 per MWh ($35.7 US). Nine provinces and two cities consume the power from it, including Shanghai.

The power distribution and transmission of the Three Gorges Dam project cost about 34.387 billion Yuan. It was completed in December 2007, one year ahead of time

 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.

In the original plan, it was expected to provide 10% of electricity consumption in China. However, China¡¯s demand for electricity has increased at a higher rate than was planned, and if fully operational now, it would support about 3% of the total electricity consumption in China.

Environmental Contribution of the dam

Direct reduction of air pollutant and greenhouse gas emission

According to The National Development and Reform Commission of China, it takes 366 grams of coal to generate 1 kWh of electricity in China(2006).Therefore, the Three Gorges Dam will potentially reduce the coal consumption by 31 million tonnes per year, cutting the emission of 100 million tonnes of greenhouse gas,]millions of tonnes of dust, 1 million tonnes of sulfur dioxide, 370 thousand tonnes of nitric oxide, 10 thousand tonnes of carbon monoxide and a significant amount of mercury into the atmosphere.The elimination of the fossil fuel also reduces the energy consumption in mining, washing and transporting about 31 million tonnes of coal from northern China to the load centre in south and east China.

Since the Three Gorges Dam project first powered in July 10, 2003, total power production is equivalent to 84 million tonnes of standard coal and reduces carbon dioxide emission by 190 million tonnes, sulfur dioxide by 2.29 million tonnes and nitroxides by 980,000 tonnes.

Reduction of greenhouse gas due to navigation

From 2004 to 2007 there were total of 198 million tonnes of goods passed through the Three Gorges Dam ship locks. The freight capacity of the river increased 6 times and the cost of shipping reduced by 25%, compared to previous years, which reduces carbon dioxide emission by 630,000 tonnes. Comparing to highway transportation, the amount of fuel that Three Gorges Dam project saved between the year of 2004 and 2007 is equivalent to 4,100,000 tonnes of standard coal. Thus it reduces carbon dioxide emission by 10 million tones.

Reforestation

The Three Gorges Dam pushes the Chinese government to think seriously about the environmental issues associated with the dam, such as deforestation and water pollution. ¡°The FAO¡¯s research suggests that the Asia-Pacific region will overall, gain about 6,000 square km of forest in 2008.That is quite a turnaround from the 13,000 square km net loss of forest each year in the 1990s. The main reason is China¡¯s huge reforestation effort. This accelerated after terrible floods in 1998 convinced the government that it must restore tree cover, especially in the mighty Yangtze¡¯s basin¡± upstream of the Three Gorges Dam.

Waste management

Since the construction of the Three Gorges Dam, many waste water treatment plants have been completed to reduce the water pollution from the large populated city Chongqing and the suburban area around it. According to the ministry of environmental protection of PRC, until April 2007, there were more than 50 waste water treatment plants installed and the total capacity reached 1.84 million tonne per day. More than 65% of the waste water is treated before being dumped into the Three Gorges Dam reservoir. About 32 land sites deposit were completed and could handle 7664.5 tonne of solid waste every day.

Flood control and drought relief

The most significant function of the dam is to control flooding, which is a major problem of a seasonal river like the Yangtze. Millions of people live downstream of the dam, and many large and important cities like Wuhan, Nanjing and Shanghai lie next to the river. Plenty of farm land and the most important industrial area of China are built beside the river.

In 1954 the river flooded 47.75 million acres (193,000 km²) of land, killing 33,169 people and forcing 18,884,000 people to move. The flood covered Wuhan, a city with 8 million people, for over three months, and the Jingguang Railway was out of service for more than 100 days.[4]

In the event of a recurrence of the 1954 flood that carried 50 billion m3 of water, the Three Gorges Dam could only divert the water above Chenglingji, leaving 30 to 40 billion m3 of flood water to be diverted.Also the dam will not protect the large tributaries such as the Xiangjiang, Zishui, Yuanshui, Lishui, Hanjiang, and Ganjiang from flooding,due to the location of the dam.

In 1998 a flood in the same area caused billions of dollars in damage. The Chinese government asked for support from its military to fight the flooding. Two thousand and thirty-nine square kilometers of farm land was flooded. The flood affected more than 2.3 million people, and 1,526 were killed.

The reservoir's flood storage capacity is 22 cubic kilometers (18 million acre feet). This capacity will reduce the frequency of major downstream flooding from once every 10 years to once every 100 years. With the dam, it is expected that major floods can be controlled. If a "super" flood comes, the dam is expected to minimize its effect.

Navigation

The installation of ship locks is intended to increase river shipping from 10 million to 100 million tonnes annually, with transportation costs cut by 30 to 37%. Shipping will become safer, since the gorges are notoriously dangerous to navigate. Each of the two ship locks is made up of 5 stages taking around 4 hours in total to complete and have a capacity of 10,000 tons.Critics argue, however, that heavy siltation will clog ports such as Chongqing within a few years based on the evidence from other dam projects.

The locks are designed to be 280 m long, 35 m wide, and 5 m deep (918 x 114 x 16.4 ft). That is 30 m longer than those on the St Lawrence Seaway, but half as deep. Before the dam was constructed, the maximum freight capacity of the river at the Three Gorges site is 18.0 million tonnes per year. From year 2004 to 2007, there were total of 198 million tonnes of freight passed through the Three Gorges Dam ship locks. The freight capacity of the river increased 6 times and the cost of shipping reduced by 25%, comparing to the previous years. The total capacity of the ship locks is expected to reach 100 million tonnes.

In addition to the canal locks, the Three Gorges Dam will be equipped with a ship lift, a kind of elevator for vessels.The ship lift will be capable of lifting ships of up to 3,000 tons.In the original plan its capacity was to be 10,000  The ship lift was not yet complete when the rest of the project was officially opened on May 20, 2006.Construction of the ship lift started in October 2007 and will be completed in the year 2014.

Relocation of local residents

The relocation of local residents is the central part of the Three Gorges Dam Project. It is considered as important as the construction of the dam. During the planning stages in the 1990s it was estimated that 1.13 million residents would be forced to relocate; new developments have doubled that number to 2.3 million.That estimate has been increased and as of 13 October 2007, 1,400,000 citizens have been displaced, which is 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 will be relocated out of Hubei province to eastern provinces and some central provinces, and the majority of the remaining people will be 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.

On one hand, the massive relocation demonstrates the Chinese government's determination and will to complete the huge project. On the other hand, there have been accusations that corruption in the government has kept residents from getting proper assistance. For instance, millions in tax money sent to the town of Gaoyang for the purpose of relocation 13,000 farmers disappeared after it was sent to the local government, and residents were denied compensation.