Yangtze

I

Introduction

Yangtze or Chang Jiang, river in China, the longest river of Asia and the third longest river in the world. The Yangtze flows a total distance of 6,300 km (3,900 mi), from the Tibetan Plateau in the west to the East China Sea in the east, forming China’s principal navigable waterway and a natural boundary between what is traditionally considered northern and southern China.

The Yangtze has immense economic importance in China. It provides irrigation water for agriculture, a source of hydroelectric power, a waterway for cargo vessels, scenic points of interest for tourism, and a great transportation network through the heart of some of the most densely populated and economically important areas in China. Shanghai, China’s most important port, commands the entrance to the Yangtze Basin, which drains an area of 1,940,000 sq km (750,000 sq mi) and contributes nearly half of China’s crop production. Some of China’s most important industrial centers are located on the Yangtze, including Wuhan and Chongqing. Many dams have been constructed in the Yangtze Basin. In 1994 construction began on the Three Gorges Dam, which will rank as the world’s largest hydroelectric dam when it is completed in 2009.

The Yangtze Basin has a seasonal semitropical climate everywhere except in the mountains of the Tibetan Plateau, where the river’s headwaters originate. Although glacier melt forms the headwaters, rain provides most of the Yangtze’s water volume. The monsoon season brings heavy rains between March and August in the river’s lower and middle courses, and from May to September in its upper course. Both floods and droughts are common in the basin. Floods generally occur every two or three years. Floods in the monsoon season are associated with heavy rainfall in the upper basin, tropical cyclones, and increased water flow from large tributaries such as the Han. In addition to large floods, the Yangtze suffers a number of environmental problems, including slope erosion, sedimentation, and industrial and organic pollution from large cities.

In China the Yangtze is known as the Chang Jiang (Long River). It has many local names as well. In the high mountains of the Tibetan Plateau, it is called the Tongtian He (River to Heaven). Upstream from Yibin, it is known as the Jinsha Jiang (Golden Sand River). The river came to be known by Europeans as the Yangtze (also spelled Yangzi), probably after a local name for the river in its lower course.

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II

Course of the Yangtze

The Yangtze flows through nine provinces and forms the eastern border of the Tibet Autonomous Region (TAR). The course of the Yangtze is traditionally divided into three sections. The mountainous Upper Yangtze is the course from the headwaters in western Qinghai Province to the city of Yichang in Hubei Province. The Middle Yangtze flows through a flat plain from Yichang to Hukou in Jiangxi Province. The Lower Yangtze stretches from Hukou to the East China Sea.

A

Upper Yangtze

The Yangtze originates in the mountains of southwestern Qinghai Province, located in the northern Tibetan Plateau. The river has three headwaters, the highest of which descends from an elevation of more than 6,600 m (21,600 ft). Their combined waters form the Tuotuo River, which flows eastward, is joined by the Dam Qu, and becomes the Tongtian. The Tongtian descends sharply from the high plateau. Downstream, where it is known as the Jinsha, the river flows through deep gorges southward, paralleling the narrow valleys of the Mekong and the Salween rivers to the west, and forming the border between the Tibet Autonomous Region (TAR) and Sichuan Province. Farther south, at Shigu in Yunnan Province, it reverses course to flow northward, then at the border of Sichuan and Yunnan provinces, again reverses course to flow southward. After this zigzag in its course, the river flows generally northeast.

In this section of its course, the Yangtze flows through deep gorges, becoming turbulent and dangerous. Near the city of Lijiang in Yunnan Province, the river reaches a depth of nearly 4,000 m (13,000 ft) in the Hutiao Xia (Tiger Leaping Gorge). The Yangtze then flows into southern Sichuan Province, where it receives the waters of the Yalong. After marking the boundary between Yunnan and Sichuan provinces for about 800 km (about 500 mi), the Yangtze enters the Sichuan Basin where it is joined by three major tributaries—the Min, Jialing, and Wu—and becomes known as the Chang Jiang. The city of Chongqing is located at its confluence with the Jialing.

Beyond Chongqing, the Yangtze flows northeast through a mountainous area up to Wan Xian, where it turns east to drop steeply through three gorges. The first and the narrowest gorge, Qutang Xia, is 8 km (5 mi) long. The middle gorge, Wu Xia, is 40 km (25 mi) long and bounded by high cliffs. The last gorge, Xiling Xia, is the longest at 75 km (46 mi). The gorges, known collectively as San Xia (Three Gorges), are considered one of the most scenic stretches of the river. However, the Three Gorges Dam under construction near the city of Yichang is expected to significantly alter the appearance of the gorges. The reservoir created by the dam will inundate many settlements and river features in the gorges.

B

Middle Yangtze

Near Yichang, still about 2,000 km (1,250 mi) from its mouth, the Yangtze drops to an elevation of only 40 m (130 ft). The river then flows at a width of up to 2 km (up to 1.2 mi) and an average depth of between 6 and 15 m (20 and 50 ft) through a large plain with many lakes. This area is prone to severe flooding and accumulation of river sediment (silt). In full summer flood, many of the lakes merge with the river. Dongting Hu and Poyang Hu, which are connected to the Yangtze, are the biggest lakes in China. They historically helped alleviate flooding by receiving overflow of the Yangtze. However, sediment from the river as well as farming and urban encroachments have reduced the water capacity of the lakes. Sedimentation and flooding also pose problems for local farmers and the area’s major cities of Jingzhou, Wuhan, and Jiujiang. Wuhan is a major port situated at the confluence of the Han and Yangtze rivers.

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