Yangtze - Geography.

Yangtze - Geography. 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. 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. C Lower Yangtze From the city of Hukou, located on the Yangtze where it meets the connection from Poyang Hu, the river flows on a gentle downward slope, first through plains and hills and then through a coastal wetland with numerous shallow lakes. It also passes through or near a number of large cities: Anqing, Nanjing (near the Yangtze's tidal limit), Zhenjiang (near which the Grand Canal crosses the Yangtze), and lastly Shanghai, which is located on the Huangpu River, a tributary, about 23 km (about 14 mi) south of the Yangtze. Near its mouth on the East China Sea, the Yangtze becomes relatively shallow and wide, stretching 15 km (9 mi) across where it meets the sea. The large delta of the Yangtze is subject to tidal fluctuations and contains many islands. The largest island, Chongming, is 100 km (60 mi) long. III ECONOMIC SIGNIFICANCE The Yangtze Basin has functioned as the economic heartland of China since the Tang dynasty (AD 618 to 907). A Agriculture and Industry Today about 400 million people, or about one-third of the population of China, live in the Yangtze Basin. Many are engaged in agriculture. The basin contributes nearly half of China's crop production, although only one-quarter of the basin is arable. The most fertile areas for farming are the Sichuan Basin, the plains between the Yangtze and its tributary the Han, and the plains of the lower basin. In all about 40 percent of the cereals, more than 30 percent of the cotton, nearly half of the freshwater fish, and 40 percent of the industrial production of China come from the Yangtze Basin. Food crops grown in the basin include rice, wheat, corn (maize), barley, sweet potatoes, and legumes. The rapid extension of irrigation since 1949 has led to increased double cropping of rice in the region and a rise in production. The most important industrial crop is cotton. The Yangtze Basin has deposits of most minerals required by industry, particularly coal, iron, copper, antimony, manganese, tungsten, and tin. Natural gas and oil are found in Sichuan Province. Since 1949 the treaty port cities have been transformed from centers for the collection of raw materials for export through Shanghai into industrial centers. Shanghai and Nanjing have become the nuclei of a metropolitan area producing textiles, ships, iron and steel, and fertilizers. Wuhan is a major metallurgical center. In the province of Sichuan, an industrialized area has developed around Chongqing and Chengdu, producing cement, fertilizers, and iron and steel products. B Transportation and Tourism For thousands of years, the Yangtze has been the main transport artery for people and freight moving between Sichuan Province and China's eastern coast. The Grand Canal of eastern China, constructed in stages beginning in the 5th century BC, connected northern China and areas of southern China to the Yangtze system. The Grand Canal was vital for transporting grain, soldiers, and officials until the 20th century, when railways and roads reduced its importance. Today the Yangtze continues to be an extremely important inland waterway for commerce and industry. Oceangoing vessels can reach as far inland as Wuhan, and large cargo and passenger boats can reach Chongqing. Small boats travel farther upriver to Xinshezhen, about 3,000 km (about 1,860 mi) from the sea. The traditional boats called junks, less economical than steamboats, are now rarely seen on the river. However, the development of railways has reduced transportation along the Yangtze. Before 1949 railroads running north-south were interrupted by the river. Goods and passengers had to cross by ferry. Several railroad bridges have been built since then. The two oldest bridges, crossing at Wuhan and Nanjing, were completed in 1956 and 1968, respectively. Other railroad bridges are located at Chongqing and near Kunming. In the 1970s a rail line was constructed parallel to the river from Wuhan to Chongqing. The Yangtze is also associated with tourism, both national and international. Guided boat tours through the scenic Three Gorges have developed into a thriving tourism industry. The many historical, religious, and mythological sites along the Yangtze attract many Chinese visitors. Large cities on the river, especially Shanghai, offer tourist attractions as well. C Three Gorges Dam A number of dams and canal networks meet the high regional demand for irrigation and electricity. Thousands of dams are located in the Yangtze Basin, but only two of them--the Three Gorges Dam and Gezhou Dam--are on the Yangtze itself. The Three Gorges Dam is at Sanduping, near Yichang. When completed, the dam will measure more than 200 m (600 ft) high and 1.6 km (1 mi) long, making it the largest in the world. The dam is designed to generate about 18,000 megawatts of electricity--more than any other hydroelectric facility in the world--that will be distributed throughout central China. The dam is also designed to control flooding and improve navigation upriver. The dam will create a reservoir 650 km (400 mi) long, from Yichang, through the Three Gorges, and to Chongqing. The government of the People's Republic of China has characterized the Three Gorges Dam as a source of national pride and a necessary project to provide the growing population of the region with electricity, irrigation water, and flood control. However, the massive project has drawn much criticism, both nationally and internationally. Ultimately, the new reservoir will inundate many towns and cities, displacing an estimated 1 million to 2 million people. A number of archaeological sites along the river will be submerged. Tourism associated with the Three Gorges as a physical and cultural attraction may come to an end. Scientists predict the Three Gorges Dam may have many adverse environmental effects. The dam may put stress on the fragile upper slopes of the gorges, leading to their erosion. The reservoir may accumulate sediments and industrial pollutants, and the control on water and sediment may affect the river downstream, leading to increased silting of its mouth and pollution of the delta. A plan to divert water from the Yangtze to water-short northern China may accelerate these problems. In addition, the dam may not entirely solve flooding problems. However, the dam may lessen the dependency on coal for power generation and thereby improve regional air pollution. IV HISTORY The Yangtze has long functioned as a transportation artery, as a strategic boundary, and as the lifeline of a productive agricultural region. Although most of the river has been known for a long time, the Jinsha was first recognized as the headstream in the 16th century. In the 18th century, a Qing government expedition reached the Tibetan Plateau in search of the headwaters. The headwaters were only properly mapped in the 1970s and 1980s. The Three Gorges were charted by Captain Cornell Plant of the Chinese Imperial Maritime Customs Service in the early 20th century. The river is intricately associated with benchmark events in Chinese history. Some of these include the warfare between the Three Kingdoms in the 3rd century, the Taiping Rebellion (1851-1864) that spread along the Grand Canal and the Yangtze, and the Japanese military advance and destruction along the river before and during World War II (1939-1945). In the civil war of the 1940s between Chinese Communists and the Kuomintang (Nationalists), Communist forces under Mao Zedong made many strategic crossings of the river and its tributaries. The Communists drove the Kuomintang from the mainland and formed the People's Republic of China in 1949. Mao Zedong used the Yangtze to build the cult of himself as a great hero by swimming across it at Wuhan in 1956, 1958, and 1966. Economic development of the Yangtze Basin received a major boost from northern extensions of the Grand Canal between the 7th and 14th centuries. The canal provided an efficient means of transporting the agricultural products of the Yangtze Basin to northern China and, especially, the national capital, Beijing. In the 19th century, Shanghai and inland settlements developed as ports of trade with some connections to Western markets. Numerous references to the Yangtze are found in Chinese mythology and literature. Many sites on the Yangtze are locations of incidents described in the well-known 14th-century novel Sanguozhi yanyi (The Romance of the Three Kingdoms). Chinese poets have written extensively about the beauty of the middle and lower Yangtze and the hazards of the gorges. Mao Zedong wrote a poem in praise of human ability to control the river. Contributed By: Avijit Gupta Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.