SAN-MEN GORGE

Wade-Giles romanization San-men-hsia, Pinyin Sanmenxia gorge enclosing the Huang Ho (Yellow River) at a site in western Honan sheng (province), China. The gorge is the site of a great dam and hydroelectric installation on which work was begun in the 1950s. The gorge is some 20 miles (30 km) east of the city of San-men-hsia. At the gorge the Huang Ho narrows to flow between steep cliffs, and the current is further impeded by two rocky islandsKuei-men and Shen-menwhich divide the stream into three channels, known as the Gate of Ghosts (Kuei Men), the Gate of the Spirits (Shen Men), and the Gate of Man (Jen Men). Below these the river is somewhat obstructed by three smaller islandsTi-chu Rock, Chang-kung-shih Island, and Shu-chuang-t'aithe last two being connected by extensive sandbanks on the northeast bank below the rapids. The San-men Gorge is the point at which the Huang Ho descends onto the North China Plain, afterward becoming a slow-moving and meandering river. From earliest times this difficult passage, known as Ti-chu, has constituted the principal obstacle to navigation on the Huang Ho. Of the three channels, only the Gate of Man on the eastern bank was normally passable by ships, while the Gate of Ghosts was completely impassable. Under the Former Han dynasty (206 BCAD 8), when the imperial capital was at Ch'ang-an (modern Hsi-an) in Shensi province on the Wei River, various attempts were made to widen the channel and thus permit river traffic to pass from the grain-rich North China Plain westward to the capital, but all of these ended in failure. When, under the T'ang dynasty (618907), Ch'ang-an once again became capital of a united empire, the need to overcome the obstacles became even more acute. During the late 7th and early 8th centuries, tracking paths were constructed on the cliffs of the north bank, many of them supported on trestles built into the bank, in order to enable ships to be hauled up the rapids. In the 730s, when the transportation system was improved, an attempt was made to construct a road through the hills on the north bank suitable for cart traffic, thus connecting transshipment granaries above and below the rapids. In 743 an attempt was made to cut a completely new channelremnants of which exist todayto the west of the Gate of Man. This channel, however, known as K'ai-yan-hsin River (the New River of the K'ai-yan period ), was rapidly blocked by silt. As a result of the failure of attempts to make the San-men Gorge passable to shipping, transport from the Wei River valley to the plain generally continued to travel overland from Lo-yang along the Ku River valley to Shan-hsienroughly the route that is followed in modern times by the Lung-hai Railway. In 1955, under a multipurpose plan for the permanent control of the Huang Ho, it was decided to build an enormous dam 295 feet (90 m) high across the river at San-men Gorge to act as a flood-control, silt-retention, and water-storage project and also to feed a hydroelectric station joined by a high-tension grid to the rapidly expanding industrial bases of Hsi-an, T'ai-yan, Lo-yang, and Cheng-chou. The dam has formed a reservoir of 1,350 square miles (3,500 square km), which reaches up the Huang Ho to the region of Lin-chin, Shansi, and well up the valleys of the Lo and Wei tributaries to the west. The reservoir flooded a densely populated area and required the resettlement of several hundred thousand people. The enormous silt load of the Huang Ho is now mostly deposited in this new lake, which will itself probably silt up before the mid-21st century. The formation of the dam has made it possible to regulate the flow of floodwater into the North China Plain and to maintain the water level of the Huang Ho during the winter drought while also making navigation and irrigation possible. As a generator of electricity, though, the dam has proved a disappointment. The withdrawal of Soviet assistance after 1960 delayed completion of the project, and the enormous accumulation of silt in the reservoir has since cut generating capacity.