Yangtze River

The Yangtze is a very long river in China.

It starts high in icy mountains. It rushes through deep, rocky valleys. Then it flows slowly past farms and big cities to the sea.

The Yangtze is the longest river in China and in all of Asia, and the third longest in the world, about 6,300 kilometers. In China it is called Chang Jiang, the Long River. It begins in glacier meltwater in the Tanggula Mountains on the Plateau of Tibet and flows east all the way across China to the East China Sea.

More than three-fourths of its course runs through mountains. Its basin covers about 1.8 million square kilometers, and Britannica says nearly one-third of China's people live there. The basin is China's great granary: it grows more than two-thirds of the country's rice. Shanghai, China's most populous city, stands at its mouth.

Britannica ranks the Yangtze as the longest river in China and Asia and the third longest in the world, at about 6,300 km, with a basin of 1,808,500 km² stretching some 3,200 km west to east. From its source on the Plateau of Tibet to the East China Sea it crosses or borders 10 provinces or regions, and more than three-fourths of its course is mountainous. Its eight principal tributaries are the Yalong, Min, Jialing and Han on the left bank and the Wu, Yuan, Xiang and Gan on the right.

The Western name comes from the ancient fiefdom of Yang; in China it is Chang Jiang (Long River), also Da Jiang (Great River) or simply Jiang. The basin holds nearly one-third of China's population and produces nearly half its crops, including more than two-thirds of its rice. Settlement is uneven: the highlands of the upper basin are among China's most sparsely settled regions, while the delta has the country's highest population density, and Chengdu, Chongqing, Wuhan, Nanjing and Shanghai are among the largest cities in China.

The Yangtze starts as melting ice on high mountains.

It rushes down through very deep valleys. It squeezes through three famous gorges. Then it spreads out wide and slow, and drops mud that builds new land.

The Yangtze begins as glacier meltwater on the Plateau of Tibet, which is still being pushed up as two of Earth's plates collide. Leaving the plateau, the river, here called the Jinsha, plunges through valleys up to 3 kilometers deep. For more than 400 kilometers it runs side by side with two other great rivers, the Mekong and the Salween, all within 25 to 50 kilometers of each other.

Over its first 2,600 kilometers, the Yangtze drops more than 5,200 meters. Then it cuts through the Three Gorges, cliffs of thick limestone. Below them it spreads across a plain of lakes, and near the sea it carries so much mud that its delta grows into the sea about a mile every hundred years.

Britannica explains that the upper Yangtze drains the Plateau of Tibet, still uplifting as the Indian and Eurasian plates collide; it then descends across deeply eroded plateaus of Paleozoic and Mesozoic rocks (roughly 350 to 150 million years old), and in its lower reaches crosses Cenozoic basin fills laid down as the river migrated across them. In the Jinsha stretch it cuts valleys up to 3 km deep, and in UNESCO's Three Parallel Rivers site (2003) the Jinsha, Mekong and Salween run through gorges up to 3,000 m deep below glaciated peaks over 6,000 m. Over its first 2,600 km the river falls more than 5,200 m.

The Three Gorges, Qutang, Wu and Xiling, extend about 200 km through thick limestone; before the reservoir, their walls rose 400 to 600 m and the river was 150 to 180 m deep in places. Below Yichang the river enters a natural flood-regulating basin of lakes and channels, including Dongting Lake and Poyang, China's largest natural freshwater lake. The river carries some 430 to 500 million tons of sediment a year, and the delta, dominated by river and tidal processes, advances about a mile every century; Chongming Island formed from alluvium at the mouth.

Special animals live in and along the Yangtze.

A smiling porpoise swims in the river. Small Chinese alligators live nearby. Sadly, a river dolphin called the baiji has disappeared.

The Yangtze used to be one of only two rivers in the world with two kinds of dolphin. But in 2006 the baiji, the Yangtze river dolphin, was declared functionally extinct. WWF calls it the first whole dolphin species wiped out by human activity.

Its cousin, the Yangtze finless porpoise, still lives in the river, famous for its smiling face. Overfishing, pollution and busy boat traffic threaten it. Since 2002, WWF and its partners have reconnected more than 40 lakes to the river so fish and porpoises can move between them. The river also holds the endangered Chinese alligator and Chinese sturgeon.

WWF notes that the Yangtze was one of only two rivers with two dolphin species; the baiji was declared functionally extinct in 2006, which WWF describes as the first time an entire dolphin species was wiped out by human activity, with destruction of its food supply central to its loss. The Yangtze finless porpoise faces the same pressures: overfishing, which depletes its prey, plus pollution and ship traffic. Since 2002 WWF and partners have reconnected more than 40 floodplain lakes to the main stem to restore seasonal flows and migration, and support alternative incomes for fishers.

Britannica records hundreds of fish species in Chinese rivers, most of them in the Yangtze basin, with about 30 of economic importance, and notes that the gorges were a favored sturgeon spawning area. It lists the Chinese alligator, the finless porpoise and the Chinese sturgeon as endangered species that the Three Gorges project's changes to the river's regime could harm. UNESCO calls the Three Parallel Rivers area of the upper Yangtze an epicentre of Chinese biodiversity and one of the richest temperate regions in the world.

People have lived by the Yangtze for a very long time.

They grow lots of rice on its wet, flat land. Sometimes the river floods. People built a giant dam to help hold back the water and make electricity.

People have lived along the Yangtze for thousands of years, growing rice, cotton and wheat and catching fish. The Grand Canal, about 1,800 kilometers long, was built to carry grain from the Yangtze region to China's northern capitals; much of it dates from the 600s. Today the Yangtze is China's main waterway, with heavy ship traffic along 2,700 kilometers of river.

The river has also flooded many times. In 1931 and 1954 huge floods covered vast areas. To control floods and make electricity, China built the Three Gorges Dam, completed in 2006. It can produce about 22,500 megawatts of power, but its reservoir flooded towns and cities, and about one million people had to move.

The basin is one of China's longest-inhabited regions and its economic heart: the Grand Canal, possibly in partial use by the 4th century BCE and largely built in the 7th century CE, carried Yangtze grain to the northern capitals. Britannica counts more than 1,030 major floods in China between 206 BCE and 1960 and more than 50 especially extensive ones on the Yangtze; in 1931 six flood waves broke levees in two dozen places, flooded more than 90,000 km² and left 40 million people homeless or otherwise affected, and the 1954 flood rose higher still, though flood-control works limited its effects. Levees now line some 2,740 km of riverbank.

The Three Gorges Dam, completed in 2006 and fully operational in 2012 with about 22,500 MW of capacity, created a reservoir some 600 km long that submerged much of the gorges and let 10,000-ton ships reach Chongqing. Britannica lists the costs critics raised: flooding one of China's most scenic regions, risks to endangered species, the relocation of about one million people, sediment build-up, a seismically active and landslide-prone setting, and erosion downstream of now silt-free water. Pollution, soil erosion and land reclamation have also accelerated since 1950.