Saturday, July 26, 2008
Beijing-Hangzhou Canal , China
The Grand Canal (Chinese, Da Yunhe) in China is the world’s longest artificial waterway and the oldest canal still in existence. The 1,121-mile-long (1,794-kilometer) series of linked channels extends from Hangzhou on the southeast coast to the capital, Beijing, in the north. As an engineering achievement of the ancient Chinese, the canal compares with the more familiar Great Wall. It passes through twenty-four sophisticated locks and is crossed by sixty bridges. Most of China’s large rivers, including the Huai, the Huang Ho, the Wei, and the Yangtze flow from the west to the Pacific Ocean in the east, and the north-south Grand Canal provides a vital connector between their systems. That fact in itself presented a challenge to which the ancient builders were equal: the gradient of the canal was carefully designed and maintained by dredging to ensure that the seasonal flooding of the rivers did not inundate agricultural land along the artificial waterway. In places, dikes and levees provided further protection.
The Grand Canal—once known as the Grand Imperial Canal—had a simple reason for being. Successive emperors wanted to secure communication between the heavily populated politico-military centers of North China and the rice-producing regions of the south. This meant constructing a link that enabled the rapid deployment of troops and provided a faster, safer corridor for transporting grain and freight, free from the threat of the pirates who preyed on coastal shipping. During the Song dynasty (a.d. 960–1279), the annual grain traffic on the canal exceeded 340,000 tons (345,440 tonnes), carried by fleets of up to forty barges, lashed together up to four abreast and towed by water buffalo.
Suggested dates for the commencement of the canal vary from the fourth to the sixth century b.c. The 140-mile (225-kilometer) section traditionally known as the Shanyang Canal, from Qingjiang in northern Jiangsu to the Yangtze, probably was constructed sometime in that period and extended almost a thousand years later, during the Northern Qi dynasty (a.d. 550–576), when existing waterways were linked to form a single system. The second Sui emperor, Yang Di, launched an intensive building program between 605 and 610. He is said to have employed 6 million peasants constructing links between the Huang Ho and Yangtze Rivers. By thus joining the north and south of China, the canal allowed for the development of an integrated national economy and reestablished the power of the imperial civil service. Therefore, it is not surprising that it retained its importance during the Tang dynasty (618–907), when China was at the height of its power.
The canal was a key to trade expansion under the Tang and Song, and around 800 the center of political and economic activity slowly began to move to the south. By the twelfth century, Jiangsu arid Zhejiang Provinces had become the heart of China, and the Southern Song dynasty (1127–1279) established a capital at Hangzhou in 1138. In 1282, under the Mongols, another canal was built between the Huang Ho and the Ta-ch’ing River in northern Shantung, but several attempts to join it to the sea proved unsuccessful. Eventually the Hui-t’ung Canal was built to join the Huang Ho and the Wei Rivers. The Ming dynasty (1368–1644) reigned from Yingtian until 1421, after which the capital was returned to Beijing. The whole Grand Canal, comprising six main sections, was dredged and repaired. Since then it has been widened repeatedly, the last changes being made at the beginning of the Ch’ing dynasty in the middle of the seventeenth century.
Early in the twentieth century the Grand Canal began to fall into disuse for reasons that included the frequent flooding of the Huang Ho; the move to coastal shipping; the construction of major north-south railroads; and not least, general neglect as a result of political turmoil. However, the Communist regime started rehabilitation in 1958, and over the next eight years the canal was dredged, straightened, and widened, and a new 40-mile (64-kilometer) section was built. But it was not until the late 1980s that plans were put in hand to dredge the entire Grand Canal, reinstating it as an important highway for local and medium-distance freight vessels, especially in the south. Shallow-draft vessels—mostly barges and tourist boats—can now navigate the stretch south of the Yangtze all year-round. The section north of the Yangtze is seasonably navigable, and major works are in progress to allow bulk carriers to reach Xuzhou; beyond that, the canal remains impassable.