The Yangtze River -- the world's third-longest and China's main waterway -- begins in the Tibetan plateau and travels eastward across China, providing fresh water for 400 million people before emptying into the East China Sea at Shanghai.
Some of China's thorniest environmental problems are centered on its great rivers, which have been battered by massive damming, pollution, and habitat change. Here, Chinese policemen navigate a lake near the Zipingpu Dam, littered with debris from the May 12, 2008, earthquake in Sichuan province.
One of the oldest surviving examples of China's water diversion projects is the Grand Canal, which in some sections dates back nearly 2,400 years. The canal connects Beijing with Hangzhou, 800 miles to the south. Its original purpose was to transport rice, and parts of it are still in heavy use today.
By the 19th century, the canal fell into disrepair thanks to neglected maintenance, a major flood, and heavy pollution. Recent initiatives have been launched to clean it up. Here, a cleaning boat travels the canal near Wuxi in Jiangsu province.
Because the Grand Canal is both a UNESCO World Heritage Site and a tourist favorite, it receives far more attention and funds than any of China's other canals, which continue to face serious pollution threats from industrial wastewater and growing urban populations. In 2007, Chinese Premier Wen Jiabao called for drinking-water quality to be deemed a national priority and handled as a "state project." An OECD study published that year found that up to 300 million Chinese people drink contaminated water and 190 million suffer from water-related illnesses. Here, a worker clears trash floating in a canal in Beijing in July 2007.
A more recent example of China's canals is the South-North Water Transfer Project, which diverts water through channels from the Yangtze to the Yellow River, relieving China's flood-prone, wetter south to help the chronically drought-ridden north. The project, which was estimated to cost over $60 billion, fulfills a dream of Mao Zedong, who once said, "Southern water is plentiful, northern water scarce. If at all possible, borrowing some water would be good." The project, which has invoked environmental concerns -- for example, many worry that the increased pollution in southern waterways could be passed north -- is projected to funnel more than 12 trillion gallons of water northward annually along three different routes by 2050.
The canal pictured is part of the diversion project in Yixian in the northern province of Hebei. Farmers in the area, like the one pictured following her flock of sheep, have faced serious drought.
China has 20 percent of the world's population, yet only about 7 percent of the world's water resources -- four-fifths of which are in the south. The Yangtze River basin is the main source for water in the South-North Water Diversion Project. The Danjiangkou Reservoir, in central China's Hubei province, is the source of the middle route of the project. Here, construction crews work to maintain the Danjiangkou Dam in 2006.
China's most famous dam is the Three Gorges, located along the Yangtze in Hubei province. Its construction set 10 world records, including most efficiently flood-resistant hydropower-complex structure; largest power plant; biggest consumer of earth, stone, and concrete; highest monthly amount of concrete used; largest water discharge in history; largest capacity for flood discharge; and the largest number of people (1.13 million) who have ever been displaced for hydropower complex construction.
This photo shows 2010's biggest release of water, following devastating floods in July.
Construction began on the Three Gorges project in 1994 and lasted over a decade, as the government worked not only to build the world's largest dam, but also to handle an enormous reshuffling of human populations and a range of environmental impacts.
Three Gorges was supposed to solve a number of problems, including flood control for the consistently submerged south and clean energy for the, rapidly-growing coal-dependent eastern cities. Still, critics say that the dam has caused more problems than it has solved, including irreversible damage to local species' habitats and the larger ecosystem.
The Three Gorges is a source of intense national pride, nominated as a UNESCO World Heritage site in 2001, as well as one of China's biggest tourist attractions. Visitors can cruise down the Yangtze and marvel at its peerless size and breadth. Here, a visitor walks in front of the dam shortly after its completion in 2006.
Its beauty comes at a price, however. The dam's reservoir, which reached its maximum height in 2008, has inundated over 400 square miles of land and submerged an estimated 13 percent of the Three Gorges scenic sites along the river.
Construction of the Three Gorges Dam required an enormous cofferdam, a structure that temporarily enclosed the construction site and kept water out. The cofferdam was demolished on June 6, 2006, in just 12 seconds, but required enough explosive force to topple 400 10-story buildings. Prior to the explosion, the project's general manger, Li Yong'an, reassured the public that the blast wouldn't spark an earthquake.
In this photo, workers clear floating debris near the cofferdam while demolition experts prepare to demolish it. A total of 192 tons of dynamite was reportedly used in 1,700 different locations.
Among the millions displaced by China's water projects are the 22,000 former citizens of Gongtan township in Chongqing municipality. The 1,700-year-old town had some of the most well-preserved ancient residential architecture in the Yangtze River area. Gongtan was completely submerged after the Pengshui hydropower plant was constructed along the Wujiang River, one of the Yangtze's tributaries. The township was rebuilt about a mile away. Here, a worker carries stones to rebuild some of the traditional residences on July 28, 2008. Some structures in the original town, including the diaojialou, a traditional building supported by wooden columns, were relocated to the new town, which opened to tourists in 2009.
On May 12, 2008, a 7.9-magnitude earthquake, the worst in 58 years, struck Sichuan province in western China, killing 70,000 and leaving more than 18,000 missing. Since the earthquake, a growing number of scientists, both American and Chinese, have found that it may have been triggered by the Zipingpu Reservoir, built less than a mile from a major fault line.
Above, survivors sift through the debris of collapsed houses in Beichuan County shortly after the earthquake, looking for lost friends and relatives.
While the 320 million tons of water sitting in the then four-year-old Zipingpu Reservoir, shown here, may have caused the quake, the dam itself was damaged by the quake and left with some serious cracks -- 2,000 troops were sent to stabilize it. According to some estimates, the weight of the water in the reservoir was 25 times the natural stress that tectonic movements exert in a year. Such an incident only raised more "what if" questions: What if the dam had suffered greater damage?
The Yangtze is prone to flooding -- one of the problems that Chinese water-control projects are supposed to help remedy. In this photo from September 6, 2008, the river approached the 25-meter (about 80-foot) flood line near the city of Wuhan in central China's Hubei province. This part of the country experiences heavy rain every summer, which is why the Three Gorges Dam was designed to withstand floods so intense they only happen every 10,000 years.
The dam prepares for serious flooding by closing its navigation locks during the peak flow period, which diverts water pressure to the reservoir upstream.
Floods this past summer provided the Three Gorges Dam with its greatest test since the completion of its construction. On July 20, the volume of water hitting Three Gorges reached about 70,000 cubic meters per second -- some of the fastest flowing floodwaters in over a decade. Authorities scrambled to evacuate those located along the flood's path, piled sandbags along the Yangtze's banks, and worked to drain reservoirs. The rains were abnormally heavy -- the Yangtze basin had 15 percent more rainfall in 2010 than in an average year.
Here, a Chinese worker cleans up debris of some of the buildings demolished by the floods in Wuhan on July 27.
Despite the flood-control measures promised by the dams, the 2010 floods and their resulting mudslides ultimately left at least 1,200 people dead or missing. The Three Gorges Dam was clogged by vast floating islands of debris -- in some places, the trash was so thick that people could stand on it. Here, workers clean up debris in Wuhan. The flooding caused at least $22 billion in damage and raised some uncomfortable questions about whether China's dam-building spree -- meant to lay the foundations for the country's future economic growth -- was in fact putting it in grave danger.
