SHANGHAI—For over three decades the Chinese government dismissed warnings from scientists and environmentalists that its Three Gorges Dam—the world's largest—had the potential of becoming one of China's biggest environmental nightmares. But last fall, denial suddenly gave way to reluctant acceptance that the naysayers were right. Chinese officials staged a sudden about-face, acknowledging for the first time that the massive hydroelectric dam, sandwiched between breathtaking cliffs on the Yangtze River in central China, may be triggering landslides, altering entire ecosystems and causing other serious environmental problems—and, by extension, endangering the millions who live in its shadow.
Government officials have long defended the $24-billion project as a major source of renewable power for an energy-hungry nation and as a way to prevent floods downstream. When complete, the dam will generate 18,000 megawatts of power—eight times that of the U.S.'s Hoover Dam on the Colorado River. But in September, the government official in charge of the project admitted that Three Gorges held "hidden dangers" that could breed disaster. "We can't lower our guard," Wang Xiaofeng, who oversees the project for China's State Council, said during a meeting of Chinese scientists and government reps in Chongqing, an independent municipality of around 31 million abutting the dam. "We simply cannot sacrifice the environment in exchange for temporary economic gain."
The comments appeared to confirm what geologists, biologists and environmentalists had been warning about for years: building a massive hydropower dam in an area that is heavily populated, home to threatened animal and plant species, and crossed by geologic fault lines is a recipe for disaster.
Among the damage wrought: "There's been a lot less rain, a lot more drought, and the potential for increased disease," says George Davis, a tropical medicine specialist at The George Washington University (G.W.) Medical Center in Washington, D.C., who has worked in the Yangtze River Basin and neighboring provinces for 24 years. "When it comes to environmental change, the implementation of the Three Gorges dam and reservoir is the great granddaddy of all changes."
When plans for the dam were first approved in 1992, human rights activists voiced concern about the people who would be forced to relocate to make room for it. Inhabited for several millennia, the Three Gorges region is now a major part of western China's development boom. To date, the government has ordered some 1.2 million people in two cities and 116 towns clustered on the banks of the Yangtze to be evacuated to other areas before construction, promising them plots of land and small stipends—in some cases as little as 50 yuan, or $7 a month—as compensation.
Chinese and foreign scientists, meanwhile, warned that the dam could endanger the area's remaining residents. Among their concerns: landslides caused by increased pressure on the surrounding land, a rise in waterborne disease, and a decline in biodiversity. But their words fell on deaf ears. Harnessing the power of the Yangtze has been a goal since Nationalist leader Sun Yat-sen first proposed the idea in 1919. Mao Zedong, the father of China's communist revolution, rhapsodized the dam in a poem. The mega- project could not be realized in his lifetime, however, because the country's resources were exhausted by the economic failures of the Great Leap Forward in the late 1950s and then the social upheaval of the Cultural Revolution from the mid-1960s a to the early 1970s. Four decades later, the government resuscitated Mao's plans. The first of the Yangtze's famed gorges—a collection of steep bluffs at a bend in the river—was determined to be the perfect site.
In June 2003, nine years after construction began, the state-owned China Yangtze Three Gorges Development Corporation (CTGPC) filled the reservoir with 445 feet (135 meters) of water, the first of three increments in achieving the eventual depth of 575 feet (175 meters). The result is a narrow lake 410 miles (660 kilometers) long—60 miles (97 kilometers) longer than Lake Superior—and 3,600 feet (1,100 meters) wide, twice the width of the natural river channel. Scientists' early warnings came true just a month later, when around 700 million cubic feet (20 million cubic meters) of rock slid into the Qinggan River, just two miles (three kilometers) from where it flows into the Yangtze, spawning 65-foot (20-meter) waves that claimed the lives of 14 people. Despite the devastating results, the corporation three years later (in September 2006) raised the water level further—to 512 feet (156 meters). Since then, the area has experienced a series of problems, including dozens of landslides along one 20-mile (32-kilometer) stretch of riverbank. This past November, the ground gave out near the entrance to a railway tunnel in Badong County, near a tributary to the Three Gorges reservoir; 4,000 cubic yards (3,050 cubic meters) of earth and rock tumbled onto a highway. The landslide buried a bus, killing at least 30 people.
Fan Xiao, a geologist at the Bureau of Geological Exploration and Exploitation of Mineral Resources in Sichuan province, near several Yangtze tributaries, says the landslides are directly linked to filling the reservoir. Water first seeps into the loose soil at the base of the area's rocky cliffs, destabilizing the land and making it prone to slides. Then the reservoir water level fluctuates—engineers partially drain the reservoir in summer to accommodate flood waters and raise it again at the end of flood season to generate power—and the abrupt change in water pressure further disturbs the land. In a study published in the Chinese journal Tropical Geography in 2003, scholars at Guangzhou’s South China Normal University predicted that such tinkering with the water level could trigger activity in 283 landslide-prone areas.
That is apparently what happened to the 99 villagers of Miaohe, 10 miles (17 kilometers) upstream of the Yangtze, who saw the land behind their homes split into a 655-foot- (200-meter-) wide crack last year, soon after the reservoir water level was lowered for the summer floods. Officials evacuated them to a mountain tunnel where they camped for three months.
One of the greatest fears is that the dam may trigger severe earthquakes, because the reservoir sits on two major faults: the Jiuwanxi and the Zigui–Badong. According to Fan, changing the water level strains them. "When you alter the fault line's mechanical state," he says, "it can cause fault activity to intensify and induce earthquakes."
Many scientists believe this link between temblors and dams—called reservoir-induced seismicity—may have been what happened at California's Oroville Dam, in the foothills of the Sierra Nevada. The largest earthen dam in the U.S., it was constructed on an active fault line in the 1950s and filled in 1968. Seven years later, when the reservoir's water supply was restored to full capacity—after engineers lowered it 130 feet (40 meters) for maintenance—the area experienced an unusual series of earthquakes. U.S. Geological Survey seismologists subsequently found a strong link between the quakes and the refilling of the reservoir.
The Oroville area was sparsely populated, so little damage was done. But earthquakes have also been connected to past hydropower projects in China, where dams are often located in densely populated and seismically active river basins. Engineers in China blame dams for at least 19 earthquakes over the past five decades, ranging from small tremors to one near Guangdong province's Xinfengjiang Dam in 1962 that registered magnitude 6.1 on the Richter scale—severe enough to topple houses.
Surveys show that the Three Gorges region may be next. Chinese Academy of Engineering scholar Li Wangping reports on the CTGPC's Web site that the area registered 822 tremors in the seven months after the September 2006 reservoir-level increase. So far, none have been severe enough to cause serious damage. But by 2009, the dam's water level is set to be raised to its full 575-foot capacity and then lowered about 100 feet (30 meters) during flood season. That increase in water pressure, in water fluctuation and in land covered by the reservoir, Fan says, makes for a "very large possibility" that the situation will worsen.
Local news media report that whole villages of people relocated to make room for the dam will have to move a second time because of the landslides and tremors, indicating that officials failed to foresee the full magnitude of the dam's effects. Guangzhou's Southern Weekend late last year reported that villagers in Kaixian County were eager to move again, citing landslides, mudslides and ominous cracks that had appeared in the ground behind their homes. They also hoped that moving might resolve land allocation issues: Some said they received only half of the acreage they had been promised.
The dam is also taking a toll on China's animals and plants. The nation—which sprawls 3.7 million square miles (9.6 million square kilometers)—is home to 10 percent of the world's vascular plants (those with stems, roots and leaves) and biologists estimate that half of China's animal and plant species, including the beloved giant panda and the Chinese sturgeon, are found no where else in the world. The Three Gorges area alone accounts for 20 percent of Chinese seed plants—more than 6,000 species. Shennongjia, a nature reserve near the dam in Hubei province, is so undisturbed that it is famous for sightings of yeren, or "wild man"—the Chinese equivalent of "Big Foot"—as well as the only slightly more prosaic white monkey.
That biodiversity is threatened as the dam floods some habitats, reduces water flow to others, and alters weather patterns. Economic development has spurred deforestation and pollution in surrounding provinces in central China, endangering at least 57 plant species, including the Chinese dove tree and the dawn redwood. The reservoir created by Three Gorges dam threatens to flood the habitats of those species along with over 400 others, says Jianguo Liu, an ecologist at Michigan State University and guest professor at the Chinese Academy of Sciences who has done extensive work on biodiversity in China.
The dam further imperils delicate fish populations in the Yangtze. Downstream, near where the river empties into the East China Sea, the land around the Yangtze contains some of the densest clusters of human habitation in the world, and overfishing there has already endangered 25 of the river's 177 unique fish species. According to a 2003 letter to Science by Wuhan University ecologist Ping Xie, many of these fish evolved over time with the Yangtze flood plain. As the dam decreases flooding downstream, it will fragment the network of lakes around the middle as well as lower the Yangtze's water level, making it difficult for the fish to survive. The project has already contributed to the decline of the baiji dolphin, which is so rare that it is considered functionally extinct.
The reservoir could also break up land bridges into small islands, isolating clusters of animals and plants. In 1986, Venezuela's Raúl Leoni Dam flooded 1,660 square miles (4,300 square kilometers) of land, creating the vast Lake Guri, along with a scattering of nonsubmerged land. The nascent islands lost 75 percent of their biological species within 15 years, according to research published in Science.
To determine the true toll, the Three Gorges Dam is taking on animal and plant species, Liu says, long-term data is needed, so that decreases in population totals can be compared with natural species fluctuation. But he cautions that many of the dam's effects may not be immediately apparent. The project is altering reproduction patterns, meaning it may already be too late for some plants and animals. "In the short term, you see the species still there, but in the long term you could see [them] disappear," Liu says. It is here that State Council representative Wang's allusion to "hidden dangers" rings especially true.
Disease and Drought
When officials unveiled plans for the dam, they touted its ability to prevent floods downstream. Now, the dam seems to be causing the opposite problem, spurring drought in central and eastern China. In January, the China Daily (the country's largest English-language newspaper) reported that the Yangtze had reached its lowest level in 142 years—stranding dozens of ships along the waterway in Hubei and Jiangxi provinces. An unnamed official with the Yangtze River Water Resources Commission blamed climate change, even as he acknowledged that the dam had reduced the flow volume of the river by 50 percent. To make matters worse, China is now plowing ahead with a controversial $62-billion scheme to transfer water from the Yangtze to northern China, which is even more parched, through a network of tunnels and canals to be completed by 2050.
Meanwhile, at the mouth of the Yangtze residents of Shanghai, China's largest city, are experiencing water shortages. The decreased flow of fresh water also means that saltwater from the East China Sea now creeps farther upstream. This, in turn, seems to be causing a rise in the number of jellyfish, which compete with river fish for food and consume their eggs and larvae, thereby threatening native populations that are already dwindling as a result of overfishing. In 2004, a year after the dam was partially filled, scientists noted a jellyfish species in the Yangtze that had previously only reached the South China Sea.
The effects of the dam's disturbance of whole ecosystems could reverberate for decades. G.W.'s Davis is part of a project researching the disease schistosomiasis (a.k.a. snail fever or swimmer's itch), a blood parasite transmitted to humans by snails; people can get it by swimming or wading in contaminated fresh water when infected snails release larvae that can penetrate the skin. (Symptoms include fever, appetite and weight loss, abdominal pain, bloody urine, muscle and joint pain, along with nausea, a persistent cough and diarrhea.) The snails used to breed on small flood plain islands where annual flooding prevented a population explosion. Now, the decreased flow downstream from the dam is allowing the snails to breed unchecked, which has already led to a spike in schistosomiasis cases in some areas.
According to Davis, such alterations could precipitate a rise in other microbial waterborne diseases as well. "Once you dramatically change the climate and change water patterns, as is now seen in the Three Gorges region," he says, "you change a lot of environmental variables. Almost all infectious diseases are up for grabs."
The official recognition of the dam's dangers suggests that the project's environmental and public health impacts are starting to sink in. Political analysts speculate that President Hu Jintao and Premier Wen Jiabao are eager to distance themselves from a project they inherited. Although halting plans at this point would be an admission of government error, the openness following the Chongqing meeting raised the hopes of worried scientists that officials would take action to minimize the project's environmental and public health fallout.
Government-funded institutions have been quietly assessing possible recourses. Officials say they've spent more than $1.6 billion on fortifying landslide-prone areas and will spend an additional $3.2 billion on water cleanup over the next three years. In January the CTGPC signed a memorandum of understanding with the Nature Conservancy allowing that organization to consult on species protection and river health in the dam area. China's Ministry of Health, meanwhile, is trying to control schistosomiasis infections with a combination of drugs and applications of molluscicides, pesticides that wipe out the disease's snail carriers.
But these measures may not be sufficient to avert disaster. In February China's State Environmental Protection Administration said reservoir water quality targets had not been reached despite a cleanup effort that had been underway since 2001. And fighting schistosomiasis requires a more holistic, multi-pronged approach—particularly now that ecosystems in the Three Gorges region have been altered. To ward off an outbreak, Davis says, the government would have to prevent the use of night soil as fertilizer, build cement irrigation ditches, and ensure area villagers access to clean water. So far, that hasn't happened.
In the wake of media reports about the government's concerns, officials began to backpedal. In a November 2007 interview with state news agency Xinhua, State Council's Wang claimed that "no major geological disasters or related casualties" had occurred since the reservoir's water level was raised in 2006; five days later, the earth in Badong crumbled and the railroad tunnel landslide wiped out the bus and its passengers.
Following a brief period of openness, discussion of the dam's environmental effects has once again become largely taboo in China. Government officials fear that continued free discussion of the project's ramifications could lead to civil unrest. One internationally published Chinese scientist working in the Yangtze Basin declined to comment publicly, noting, "This is a very sensitive topic…. I can't give hypotheses."
Despite the Three Gorges dam's growing list of problems, however, hydropower remains an integral—and ostensibly green—component of China's energy mix. China still draws 82 percent of energy from coal, but large dams are crucial to the country's climate change program, which aims to increase its proportion of electricity from renewable resources from the current 7.2 percent to 15 percent by 2020. Over one third of that will come from hydropower—more than from any other source. Twelve new dams are planned for the upper Yangtze alone.
The logistical and environmental hurdles involved in executing these dams underscore China's commitment to hydropower. The Yangtze's newest dams include several smaller projects that are necessary to alleviate sedimentation caused by the Three Gorges reservoir. In his 2007 report to the National People's Congress, Prime Minister Wen Jiabao said that China had relocated 22.9 million people to make room for its large hydroprojects.
China's original goal was to fill the reservoir to its maximum level by 2013. Despite all the trouble, that target was moved up to 2009, Fan says, to boost hydropower output by an additional 2.65 billion kilowatt-hours each year.
"For the economic interests and profit of the Three Gorges Project Development Corporation," he says, "that's very important. But the function of any river, including the Yangtze, is not only to produce power. At the very least, [a river] is also important for shipping, alleviating pollution, sustaining species and ecosystems, and maintaining a natural evolutionary balance."
"The Yangtze doesn't belong to the Three Gorges Project Development Corporation," Fan adds. "It belongs to all of society."
|Three Gorges Dam|
The dam in September 2009
Location in China
|Location||Sandouping, Yiling, Hubei|
|Coordinates||30°49′23″N111°00′12″E / 30.82306°N 111.00333°E / 30.82306; 111.00333Coordinates: 30°49′23″N111°00′12″E / 30.82306°N 111.00333°E / 30.82306; 111.00333|
|Purpose||Power, flood control, navigation|
|Construction began||December 14, 1994|
|Construction cost||¥180 billion (US$27.6 billion)|
|Owner(s)||China Yangtze Power (subsidiary of China Three Gorges Corporation)|
|Dam and spillways|
|Type of dam||Gravity dam|
|Height||181 m (594 ft)|
|Length||2,335 m (7,661 ft)|
|Width (crest)||40 m (131 ft)|
|Width (base)||115 m (377 ft)|
|Spillway capacity||116,000 m3/s (4,100,000 cu ft/s)|
|Creates||Three Gorges Reservoir|
|Total capacity||39.3 km3 (31,900,000 acre⋅ft)|
|Catchment area||1,000,000 km2 (390,000 sq mi)|
|Surface area||1,084 km2 (419 sq mi)|
|Maximum length||600 km (370 mi)|
|Normal elevation||175 m (574 ft)|
|Hydraulic head||Rated: 80.6 m (264 ft)|
Maximum: 113 m (371 ft)
|Turbines||32 × 700 MW|
2 × 50 MW Francis-type
|Installed capacity||22,500 MW|
|Annual generation||87 TWh (310 PJ) (2015)|
The Three Gorges Dam is a hydroelectricgravity dam that spans the Yangtze River by the town of Sandouping, located in Yiling District, Yichang, Hubei province, China. The Three Gorges Dam is the world's largest power station in terms of installed capacity (22,500 MW). In 2014 the dam generated 98.8 terawatt-hours (TWh) and had the world record, but was surpassed by Itaipú Dam that set the new world record in 2016 producing 103.1 TWh.
Except for the locks, the dam project was completed and fully functional as of July 4, 2012, when the last of the main water turbines in the underground plant began production. The ship lift was complete in December 2015. Each main water turbine has a capacity of 700 MW. The dam body was completed in 2006. Coupling the dam's 32 main turbines with two smaller generators (50 MW each) to power the plant itself, the total electric generating capacity of the dam is 22,500 MW.
As well as producing electricity, the dam is intended to increase the Yangtze River's shipping capacity and reduce the potential for floods downstream by providing flood storage space. China regards the project as monumental as well as a success socially and economically, with the design of state-of-the-art large turbines, and a move toward limiting greenhouse gas emissions. However, the dam flooded archaeological and cultural sites and displaced some 1.3 million people, and is causing significant ecological changes, including an increased risk of landslides. The dam has been controversial both domestically and abroad.
A large dam across the Yangtze River was originally envisioned by Sun Yat-sen in The International Development of China, in 1919. He stated that a dam capable of generating 30 million horsepower (22 GW) was possible downstream of the Three Gorges. In 1932, the Nationalist government, led by Chiang Kai-shek, began preliminary work on plans in the Three Gorges. In 1939, Japanese military forces occupied Yichang and surveyed the area. A design, the Otani plan, was completed for the dam in anticipation of a Japanese victory over China.
In 1944, the United States Bureau of Reclamation head design engineer, John L. Savage, surveyed the area and drew up a dam proposal for the 'Yangtze River Project'. Some 54 Chinese engineers went to the U.S. for training. The original plans called for the dam to employ a unique method for moving ships; the ships would move into locks located at the lower and upper ends of the dam and then cranes with cables would move the ships from one lock to the next. In the case of smaller water craft, groups of craft would be lifted together for efficiency. It is not known whether this solution was considered for its water-saving performance or because the engineers thought the difference in height between the river above and below the dam too great for alternative methods. 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 takeover, Mao Zedong supported the project, but began the Gezhouba Dam project nearby first, and economic problems including the Great Leap Forward and the Cultural Revolution slowed progress. After the 1954 Yangtze River Floods, in 1956, Mao Zedong authored "Swimming", a poem about his fascination with a dam on the Yangtze River. In 1958, after the Hundred Flowers Campaign, some engineers who spoke out against the project were imprisoned.
During the 1980s, the idea of a dam reemerged. The National People's Congress approved the dam in 1992: out of 2,633 delegates, 1,767 voted in favour, 177 voted against, 664 abstained, and 25 members did not vote. Construction started on December 14, 1994. The dam was expected to be fully operational in 2009, but additional projects, such as the underground power plant with six additional generators, delayed full operation until May 2012.[verification needed] The ship lift was completed in 2015. The dam had raised the water level in the reservoir to 172.5 m (566 ft) above sea level by the end of 2008 and the designed maximum level of 175 m (574 ft) by October 2010.
Composition and dimensions
Made of concrete and steel, the dam is 2,335 m (7,661 ft) long and the top of the dam is 185 m (607 ft) above sea level. The project used 27.2×106 m3 (35.6×106 cu yd) of concrete (mainly for the dam wall), used 463,000 T of steel (enough to build 63 Eiffel Towers), and moved about 102.6×106 m3 (134.2×106 cu yd) of earth. The concrete dam wall is 181 m (594 ft) high above the rock basis.
When the water level is at its maximum of 175 m (574 ft) above sea level, 110 m (361 ft) higher than the river level downstream, the dam reservoir is on average about 660 km (410 mi) in length and 1.12 km (3,675 ft) in width. It contains 39.3 km3 (31,900,000 acre⋅ft) of water and has a total surface area of 1,045 km2 (403 sq mi). On completion, the reservoir flooded a total area of 632 km2 (244 sq mi) of land, compared to the 1,350 km2 (520 sq mi) of reservoir created by the Itaipu Dam.
The government estimated that the Three Gorges Dam project would cost 180 billion yuan (US$22.5 billion). By the end of 2008, spending had reached 148.365 billion yuan, among which 64.613 billion yuan was spent on construction, 68.557 billion yuan on relocating affected residents, and 15.195 billion yuan on financing. It was estimated in 2009 that the construction cost would be recovered when the dam had generated 1,000 terawatt-hours (3,600 PJ) of electricity, yielding 250 billion yuan. Full cost recovery was thus expected to occur ten years after the dam started full operation, but the full cost of the Three Gorges Dam was recovered by December 20, 2013.
Funding sources include the Three Gorges Dam Construction Fund, profits from the Gezhouba Dam, loans from the China Development Bank, loans from domestic and foreign commercial banks, corporate bonds, and revenue from both before and after the dam is fully operational. Additional charges were assessed as follows: Every province receiving power from the Three Gorges Dam had to pay ¥7.00 per MWh extra. Other provinces had to pay an additional charge of ¥4.00 per MWh. The Tibet Autonomous Region pays no surcharge.
Power generation and distribution
Power generation is managed by China Yangtze Power, a listed subsidiary of China Three Gorges Corporation (CTGC)—a Central Enterprise SOE administered by SASAC. The Three Gorges Dam is the world's largest capacity hydroelectric power station with 34 generators: 32 main generators, each with a capacity of 700 MW, and two plant power generators, each with capacity of 50 MW, making a total capacity of 22,500 MW. Among those 32 main generators, 14 are installed in the north side of the dam, 12 in the south side, and the remaining six in the underground power plant in the mountain south of the dam. Annual electricity generation in 2015 was 87 TWh.
The main generators weigh about 6,000 tonnes each and are designed to produce more than 700 MW of power. The designed head of the generator is 80.6 meters (264 ft). The flow rate varies between 600–950 cubic metres per second (21,000–34,000 cu ft/s) depending on the head available. The greater the head, the less water needed to reach full power. Three Gorges uses Francis turbines. Turbine diameter is 9.7/10.4 m (VGS design/Alstom's design) and rotation speed is 75 revolutions per minute. This means that in order to generate power at 50Hz, the generator rotors have 80 poles per phase, for a total of 240 poles per rotor to generate 50Hz three-phase power. Rated power is 778 MVA, with a maximum of 840 MVA and a power factor of 0.9. The generator produces electrical power at 20 kV. The electricity generated is then stepped-up to 500 kV for transmission at 50Hz. The outer diameter of the generator stator is 21.4/20.9 m. The inner diameter is 18.5/18.8 m. The stator, the biggest of its kind, is 3.1/3 m in height. Bearing load is 5050/5500 tonnes. Average efficiency is over 94%, and reaches 96.5%.
The generators were manufactured by two joint ventures: one of them Alstom, ABB Group, Kvaerner, and the Chinese company Haerbin Motor; the other Voith, General Electric, Siemens (abbreviated as VGS), and the Chinese company Oriental Motor. The technology transfer agreement was signed together with the contract. Most of the generators are water-cooled. Some newer ones are air-cooled, which are simpler in design and manufacture and are easier to maintain.
Generator installation progress
The 14 north side main generators are in operation. The first (No. 2) started on July 10, 2003. The north side became completely operational September 7, 2005 with the implementation of generator No. 9. Full power (9,800 MW) was only reached on October 18, 2006 after the water level reached 156 m.
The 12 south side main generators are also in operation. No. 22 began operation on June 11, 2007 and No. 15 started up on October 30, 2008. The sixth (No. 17) began operation on December 18, 2007, raising capacity to 14.1 GW, finally surpassing Itaipu (14.0 GW), to become the world's largest hydro power plant by capacity.
As of May 23, 2012 when the last main generator, No. 27, finished its final test, the six underground main generators are also in operation, raising capacity to 22.5 GW. After nine years of construction, installation and testing, the power plant is now fully operational.
By August 16, 2011, the plant had generated 500 TWh of electricity. In July 2008 it generated 10.3 TWh of electricity, its first month over 10 TWh. On June 30, 2009, after the river flow rate increased to over 24,000 m3, all 28 generators were switched on, producing only 16,100 MW because the head available during flood season is insufficient. During an August 2009 flood, the plant first reached its maximum output for a short period.
During the November to May dry season, power output is limited by the river's flow rate, as seen in the diagrams on the right. When there is enough flow, power output is limited by plant generating capacity. The maximum power-output curves were calculated based on the average flow rate at the dam site, assuming the water level is 175 m and the plant gross efficiency is 90.15%. The actual power output in 2008 was obtained based on the monthly electricity sent to the grid.
The Three Gorges Dam reached its design-maximum reservoir water level of 175 m (574 ft) for the first time on October 26, 2010, in which the intended annual power-generation capacity of 84.7 TWh was realized. In 2012, the dam's 32 generating units generated a record 98.1 TWh of electricity, which accounts for 14% of China's total hydro generation.
The State Grid Corporation and China Southern Power Grid paid a flat rate of ¥250 per MWh (US$35.7) until July 2, 2008. Since then, the price has varied by province, from ¥228.7–401.8 per MWh. Higher-paying customers receive priority, such as Shanghai. Nine provinces and two cities consume power from the dam.
Power distribution and transmission infrastructure cost about 34.387 billion Yuan. Construction was completed in December 2007, one year ahead of schedule.
Power is distributed over multiple 500 kilovolt (kV) transmission lines. Three direct current (DC) lines to the East China Grid carry 7,200 MW: Three Gorges – Shanghai (3,000 MW), HVDC Three Gorges – Changzhou (3,000 MW), and HVDC Gezhouba – Shanghai (1,200 MW). The alternating current (AC) lines to the Central China Grid have a total capacity of 12,000 MW. The DC transmission line HVDC Three Gorges – Guangdong to the South China Grid has a capacity of 3,000 MW.
The dam was expected to provide 10% of China's power. However, electricity demand has increased more quickly than previously projected. Even fully operational, on average, it supports only about 1.7% of electricity demand in China in the year of 2011, when the Chinese electricity demand reached 4692.8 TWh.
According to the National Development and Reform Commission of China, 366 grams of coal would produce 1 kWh of electricity during 2006. At full power, Three Gorges reduces coal consumption by 31 million tonnes per year, avoiding 100 million tonnes of greenhouse gas emissions, millions of tonnes of dust, one million tonnes of sulfur dioxide, 370,000 tonnes of nitric oxide, 10,000 tonnes of carbon monoxide, and a significant amount of mercury. Hydropower saves the energy needed to mine, wash, and transport the coal from northern China.
From 2003 to 2007, power production equaled that of 84 million tonnes of standard coal, reducing carbon dioxide by 190 million tonnes, sulfur dioxide by 2.29 million tonnes, and nitrogen oxides by 980,000 tonnes.
The dam increased the Yangtze's barge capacity sixfold, reducing carbon dioxide emission by 630,000 tonnes. From 2004 to 2007 a total of 198 million tonnes of goods passed through the ship locks. Compared to using trucking, barges reduced carbon dioxide emission by ten million tonnes and lowered costs by 25%.
Erosion and sedimentation
Two hazards are uniquely identified with the dam. One is that sedimentation projections are not agreed upon, and the other is that the dam sits on a seismic fault. At current levels, 80% of the land in the area is experiencing erosion, depositing about 40 million tons of sediment into the Yangtze annually. Because the flow is slower above the dam, much of this sediment will now settle there instead of flowing downstream, and there will be less sediment downstream.
The absence of silt downstream has three effects:
- Some hydrologists expect downstream riverbanks to become more vulnerable to flooding.
- 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.
Earthquakes and landslides
Erosion in the reservoir, induced by rising water, causes frequent major landslides that have led to noticeable disturbance in the reservoir surface, including two incidents in May 2009 when somewhere between 20,000 and 50,000 cubic metres (26,000 and 65,000 cu yd) of material plunged into the flooded Wuxia Gorge of the Wu River. Also, in the first four months of 2010, there were 97 significant landslides.
The dam catalyzed improved upstream wastewater treatment around Chongqing and its suburban areas. According to the Ministry of Environmental Protection, 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% forestation, down from 20% in the 1950s.
Research by the United NationsFood and Agriculture Organization research suggested that the Asia-Pacific region would, overall, gain about 6,000 km2 (2,300 sq mi) of forest by 2008. That is a significant change from the 13,000 km2 (5,000 sq mi) net loss of forest each year in the 1990s. The main reason is China's huge reforestation effort. This accelerated after the 1998 Yangtze River floods convinced the government that it must restore tree cover, especially in the Yangtze's basin upstream of the Three Gorges Dam.
This section needs to be updated. Please update this article to reflect recent events or newly available information.(October 2017)
Concerns about the potential wildlife impact of the dam predate the National People's Congress's approval in 1992. This region has long been known for its rich biodiversity. It is home to 6,388 species of plants, which belong to 238 families and 1508 genera. Of these plant species, 57 percent are endangered. These rare species are also used as ingredients in traditional Chinese medicines. Already, the percentage of forested area in the region surrounding the Three Gorges Dam has dropped from twenty percent in 1950 to less than ten percent as of 2002, negatively affecting all plant species in this locality. The region also provides habitats to hundreds of freshwater and terrestrial animal species. Freshwater fish are especially affected by dams due to changes in the water temperature and flow regime. Many other fish are hurt in the turbine blades of the hydroelectric plants as well. This is particularly detrimental to the ecosystem of the region because the Yangtze River basin is home to 361 different fish species and accounts for twenty-seven percent of all endangered freshwater fish species in China. Other aquatic species have been endangered by the dam, particularly the baiji, or Chinese river dolphin, now extinct. In fact, Government Chinese scholars even claim that the Three Gorges Dam directly caused the extinction of the baiji.
Of the 3,000 to 4,000 remaining critically endangeredSiberian crane, a large number currently spend the winter in wetlands that will be destroyed by the Three Gorges Dam. The dam contributed to the functional extinction of the baiji Yangtze river dolphin. Though it was close to this level even at the start of construction, the dam further decreased its habitat and increased ship travel, which are among the factors causing what will be its ultimate demise. In addition, populations of the Yangtze sturgeon are guaranteed to be "negatively affected" by the dam.
Floods, agriculture, industry
An important function of the dam is to control flooding, which is a major problem for the seasonal river of the Yangtze. Millions of people live downstream of the dam, with many large, important cities like Wuhan, Nanjing, and Shanghai situated adjacent to the river. Plenty of farm land and China's most important industrial area are built beside the river.
The reservoir's flood storage capacity is 22 cubic kilometres (18,000,000 acre⋅ft). This capacity will reduce the frequency of major downstream flooding from once every ten years to once every 100 years. The dam is expected to minimize the effect of even a "super" flood.In 1954 the river flooded 193,000 km2 (74,518 sq mi), killing 33,169 people and forcing 18,884,000 people to move. The flood covered Wuhan, a city of eight million people, for over three months, and the Jingguang Railway was out of service for more than 100 days. The 1954 flood carried 50 cubic kilometres (12 cu mi) of water. The dam could only divert the water above Chenglingji, leaving 30 to 40 km3 (7.2 to 9.6 cu mi) to be diverted. Also the dam cannot protect against some of the large tributaries downstream, including the Xiang, Zishui, Yuanshui, Lishui, Hanshui, and the Gan.
In 1998 a flood in the same area caused billions of dollars in damage; 2,039 km2 (787 sq mi) of farm land were flooded. The flood affected more than 2.3 million people, killing 1,526. In early August 2009, the largest flood in five years passed through the dam site. The dam limited the water flow to less than 40,000 cubic metres (52,000 cu yd) per second, raising the upstream water level from 145.13 metres on August 1, 2009, to 152.88 on August 8, 2009. 4.27 cubic kilometres of flood water were captured and the river flow was cut by as much as 15,000 cubic metres per second.
The dam discharges its reservoir during the dry season between December and March every year. This increases the flow rate of the river downstream, and provides fresh water for agricultural and industrial usage. It also improves shipping conditions. The water level upstream drops from 175 m to 145 m, preparing for the rainy season. The water also powers the Gezhouba Dam downstream.
Since the filling of the reservoir in 2003, the Three Gorges Dam has supplied an extra 11 cubic kilometres of fresh water to downstream cities and farms during the dry season.
During the 2010 South China floods, in July, inflows at the Three Gorges Dam reached a peak of 70,000 m3/s (2,500,000 cu ft/s), exceeding the peak during the 1998 Yangtze River Floods. The dam's reservoir rose nearly 3 m (9.8 ft) in 24 hours and reduced the outflow to 40,000 m3/s (1,400,000 cu ft/s) in discharges downstream, effectively alleviating serious impacts on the middle and lower river.
In 2010, NASA scientists calculated that shift of water mass stored by the dams would increase the length of the earth's day by 0.06 microseconds and make the earth slightly more round in the middle and flat on the poles. 
Navigating the dam
The installation of ship locks is intended to increase river shipping from ten million to 100 million tonnes annually, as a result transportation costs will be cut between 30 and 37%. Shipping will become safer, since the gorges are notoriously dangerous to navigate. Ships with much deeper draft will be able to navigate 2,400 kilometres (1,500 mi) upstream from Shanghai all the way to Chongqing. It is expected that shipping to Chongqing will increase fivefold.
There are two series of ship locks installed near the dam (30°50′12″N111°1′10″E / 30.83667°N 111.01944°E / 30.83667; 111.01944). Each of them is made up of five stages, with transit time at around four hours. Maximum vessel size is 10,000 tons. The locks are 280 m long, 35 m wide, and 5 m deep (918 × 114 × 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 at the Three Gorges site was 18.0 million tonnes per year. From 2004 to 2007, a total of 198 million tonnes of freight passed through the locks. The freight capacity of the river increased six times and the cost of shipping was reduced by 25%. The total capacity of the ship locks is expected to reach 100 million tonnes per year.
These locks are staircase locks, whereby inner lock gate pairs serve as both the upper gate and lower gate. The gates are the vulnerable hinged type, which, if damaged, could temporarily render the entire flight unusable. As there are separate sets of locks for upstream and downstream traffic, this system is more water efficient than bi-directional staircase locks.
In addition to the canal locks, there is a ship lift, a kind of elevator for vessels. The ship lift can lift ships of up to 3,000 tons. The vertical distance traveled is 113 metres, and the size of the ship lift's basin is 120×18×3.5 metres. The ship lift takes 30 to 40 minutes to transit, as opposed to the three to four hours for stepping through the locks. One complicating factor is that the water level can vary dramatically. The ship lift must work even if water levels vary by 12 meters (39 ft) on the lower side, and 30 metres on the upper side.
The ship lift's design uses a helical gear system, to climb or descend a toothed rack.
The ship lift was not yet complete when the rest of the project was officially opened on May 20, 2006. In November 2007 it was reported in the local media that construction of the ship lift started in October 2007.
In February 2012 Xinhua reported that the four towers that are to support the ship lift had almost been completed.
The report said the towers had reached 189 metres of the anticipated 195 metres, the towers would be completed by June 2012 and the entire shiplift in 2015.
As of May 2014, the ship lift was expected to be completed by July 2015. It was tested in December 2015 and announced complete in January 2016.Lahmeyer, the German firm that designed the ship lift, said it will take a vessel less than an hour to transit the lift. An article in Steel Construction says the actual time of the lift will be 21 minutes. It says that the expected dimensions of the 3,000 tonnes (3,000,000 kg) passenger vessels the ship lift's basin was designed to carry will be 84.5 metres (277 ft) X 17.2 metres (56 ft) X 2.65 metres (8.7 ft).
The trials of elevator finished in July 2016, the first cargo ship was lifted in July 15, the lift time comprised 8 minutes.Shanghai Daily reported that the first operational use of the lift was on September 18, 2016, when limited "operational testing" of the lift began.
Plans also exist for the construction of short portage railways bypassing the dam area altogether. Two short rail lines, one on each side of the river, are to be constructed. The 88 kilometer long northern portage railway (北岸翻坝铁路) will run from the Taipingxi port facility (太平溪港) on the northern side of the Yangtze, just upstream from the dam, via Yichang East Railway Station to the Baiyang Tianjiahe port facility in Baiyang Town (白洋镇), below Yichang. The 95 kilometer long southern portage railway (南岸翻坝铁路) will run from Maoping (upstream of the dam) via Yichang South Railway Station to Zhicheng (on the Jiaozuo–Liuzhou Railway).
In late 2012, preliminary work started along both future railway routes.
The great size of the reservoir and the huge relocation it caused was justified by the flood protection it provides for communities downstream. As of June 2008, China relocated 1.24 million residents (ending with Gaoyang in Hubei Province) as 13 cities, 140 towns and 1350 villages either flooded or were partially flooded by the reservoir [A_2-M:CR3-1HP:S-15], about 1.5% of the province's 60.3 million and Chongqing Municipality's 31.44 million population. About 140,000 residents were relocated to other provinces.
Relocation was completed on July 22, 2008. Some 2007 reports claimed that Chongqing Municipality will encourage an additional four million people to move away from the dam to the main urban area of Chongqing by 2020. However, the municipal government explained that the relocation is due to urbanization, rather than the dam, and people involved included other areas of the municipality.
Allegedly, funds for relocating 13,000 farmers around Gaoyang disappeared after being sent to the local government, leaving residents without compensation.
Culture and aesthetics
The 600 km (370 mi) long reservoir flooded some 1,300 archaeological sites and altered the appearance of the Three Gorges as the water level rose over 300 ft (91 m). Cultural and historical relics are being moved to higher ground as they are discovered, but the flooding inevitably covered undiscovered relics. Some sites could not be moved because of their location, size, or design. For example, the hanging coffins site high in the Shen Nong Gorge is part of the cliffs.
The United States Department of Defense reported that in Taiwan, "proponents of strikes against the mainland apparently hope that merely presenting credible threats to China's urban population or high-value targets, such as the Three Gorges Dam, will deter Chinese military coercion."
The notion that the military in Taiwan would seek to destroy the dam provoked an angry response from the mainland Chinese media. People's Liberation Army General Liu Yuan was quoted in the China Youth Daily saying that the People's Republic of China would be "seriously on guard against threats from Taiwan independence terrorists."
The Three Gorges Dam is a steel-concrete gravity dam. The water is held back by the innate mass of the individual dam sections. As a result, damage to an individual section should not affect other parts of the dam. Due to the sheer size of the dam, it is expected to withstand tactical nuclear strikes.
Days after the first filling of the reservoir, around 80 hairline cracks were observed in the dam's structure. The submerged spillway gates of the dam might pose a risk of cavitation, similar to that which severely damaged the poorly designed and cavitating spillways of the Glen Canyon Dam in the US state of Arizona, which was unable to properly withstand the Colorado river floods of 1983. However 163,000 concrete units of the Three Gorges dam all passed quality testing and the deformation was within design limits. An experts group gave the project overall a good quality rating.
Model of the Three Gorges Dam looking upstream, showing the dam body (middle left), the spillway (middle of the dam body) and the ship lift (to the right).
Model of the Three Gorges Dam showing the ship lift and the ship lock. The ship lift is to the right of the dam body with its own designated waterway. The ship locks are to the right (northeast) of the ship lift.
Earthfill south dam in foreground with view along main dam. The wall beyond is to separate spillway and turbine flows from the lock and ship lift upstream approach channel. A similar separation is used on the downstream side, seen partially in the preceding image.