YALU RIVER

Wade-Giles romanization Ya-l Chiang, Pinyin Yalu Jiang, Korean Amnok-kang river that forms the northwestern boundary between North Korea and the Northeast Region (Manchuria) of China. The Chinese provinces of Kirin and Liaoning are bordered by the river. Its length is estimated to be 491 miles (790 km), and it drains an area of some 12,259 square miles (31,751 square km). From a mountainous source in the Ch'ang-pai Mountains, the river flows southwestward to drain into the Yellow Sea. The river is an important source of hydroelectric power, is used for transportation (especially of lumber from the rich forests on its banks), and provides fish for the riverine populations. In addition to serving as a political boundary, the Yalu River constitutes a dividing line between Chinese and Korean cultures. It is generally known abroad by its Chinese name, Ya-l (Pinyin Ya-lu), instead of by its Korean name, Amnok. According to ancient writing, the Chinese name, which is derived from the words ya (duck) and l (greenish blue), is a comparison of the blueness of the river's waters and the greenish blue of a particular species of domestic duck that inhabits it. The Yalu did not become a political boundary until the KoreanChinese border was established toward the end of the Korean Koryo dynasty in the 14th century. The river played an important political role in the Korean War of 195053. The Yalu rises in T'ien Lake (known in Korean as Ch'on Lake), a body of water of indeterminate depth on top of Pai-t'ou Mountain on the ChineseNorth Korean border, at a height of 9,000 feet (2,700 m) above sea level. Winding southward as far as Hyesan, North Korea, and then meandering northwestward for 80 miles (130 km), the river reaches Lin-chiang, Kirin province, from which it flows southwestward for 200 miles (320 km) before emptying into Korea Bay. Except for small areas of basaltic lava along the easternmost part of the river's course, the Yalu flows over Precambrian rock (more than 570 million years old) before its alluvium begins to spread out as it approaches its estuary. Throughout much of its course it flows through deep, gorgelike valleys, with mountains ranging in height from 1,900 to 3,800 feet (600 to 1,200 m) above sea level rising on either bank. The principal tributaries are the Herchun, Changjin, and Tokro rivers. The upper part of the Yalu as far as Lin-chiang has very rapid currents, many waterfalls, and sunken rocks. The middle part, which extends as far as Ch'osan, contains considerable deposits of alluvium that make the riverbed so shallow in places that it prevents even timber rafts from passing downstream during the dry season. The lower part of the river's course has a very slow current in which deposits of alluvium are even greater and form a vast delta containing many islands. The silting of the river has increased so much in the past several decades that, whereas in 1910 ships of 1,000 tons could easily sail upstream to the port of Sinuiju, today 500-ton ships can hardly manage to do so. The climate along the river's course is typically continental and characterized by cold winters and warm summers. The river is frozen and thus closed to navigation during the four winter months (November through February). Because it is situated in mountain ranges and is not far from oceans, the river's basin receives fairly heavy rainfall, much of which occurs during the months of June, July, August, and September. The abundant rainfall waters rich forests of conifers as well as deciduous trees. The forests provide a sanctuary for wildlife, which includes wild boars, wolves, tigers, jaguars, bears, foxes, and such birds as ptarmigan and pheasant. The river abounds in carp and eels. It is notable that fish in two of the tributaries of the Yaluthe Herchun and Changjinare like those in the upper stream of the Amur River in China and not like those in the Yalu. It is supposed that these tributaries once were connected with the Sungari River, a tributary to the Amur, only to be separated from it and connected with the Yalu when an eruption of Pai-t'ou Mountain produced a flow of basaltic lava during the Quaternary Period (within the last 1.6 million years). Ever since a tribe called the Yojin was driven into Manchuria in the 16th century, the Korean side of the river has been inhabited only by Koreans. The northwestern (Chinese) bank is inhabited by Manchurians and Chinese. The arable land along the river amounts to no more than 220,000 acres (89,000 hectares). Rice is the main crop grown along the river's lower course; corn (maize), millet, soybeans, barley, and sweet potatoes are raised further upstream in the mountainous middle and upper reaches of the river. The river measures about 460 feet (140 m) in width and 3 feet (one metre) in depth at Hyesan and is 640 to 800 feet (200 to 250 m) wide and 4.5 feet (1.4 m) deep at Chunggang. It reaches 1,280 feet (390 m) in width at Sindojang, the location of an immense reservoir of the Sup'ung Lake hydroelectric station. In its estuary the river is 3 miles (5 km) wide and 8 feet (2.5 m) deep. The river is primarily important as a source for hydroelectricity. The largest dam on the river is located at Sup'ung-nodongjagu, North Korea, situated 35 miles (56 km) upstream from Sinuiju. The height of the dam is 320 feet (100 m) and its length 2,880 feet (880 m); the surface area of the reservoir is 133 square miles (345 square km), and its potential generating capacity amounts to about 7,000,000 kilowatts. One of the largest hydroelectric plants in eastern Asia, it supplies electricity for a large area of the northern part of North Korea as well as the southern part of the Manchurian region, both for industrial development and for electric railroads. Its importance to the Chinese economy was a major reason for the entry of the People's Republic of China into the Korean War in 1950, when United Nations troops were advancing northward toward the Yalu.