WEI RIVER

Chinese (Wade-Giles) Wei Ho, or (Pinyin) Wei He river in Kansu and Shensi provinces, China, a western tributary of the Huang Ho. It rises in the Ma-wei Mountains in the Kansu plateau, between Lin-t'ao and Wei-yan, flows east, between the north-south Lung Mountains and the east-west Tsinling Mountains, and then flows along the foot of the Tsinling to the north of Sian (Hsi-an) and Hua-yin (both in Shensi) to join the Huang Ho at T'ung-kuan (Shensi). The river's total length is approximately 537 miles (864 km). Its basin is sharply defined to the south, throughout its course, by the abrupt clifflike northern face of the Tsinling Mountains. Its drainage basin is almost entirely formed by tributaries flowing from the north and is divided into three major areas: the mountainous and arid plateau region to the west of the Lung and Liu-p'an mountain ranges in Kansu; the heavily dissected plateau-basin of Shensi, which is covered with loess; and the troughlike floodplain of its lower course. Its major tributaries in Shensi are the Ching and Lo rivers. Historically, the Wei River valley was the earliest centre of Chinese civilization and until the 10th century AD was the site of a succession of capital cities. The area around the junction of the Ching and the Wei rivers was also the site of the first ambitious irrigation works in China-the Paikung and Ch'eng-kung canal systems, built in the 3rd century BC. The Wei itself, as well as its tributaries, are heavily silt-laden and were never major waterways. To supply the capital cities in the area of Sian, canals were built paralleling the river as far as T'ung-kuan. The first of these was constructed at the beginning of the 1st century BC under the Han dynasty (206 BC-AD 220). Although this fell into disrepair, a further canal was built under the Sui dynasty (581-618). The irrigation works upon which the Wei River valley depended for its prosperity have undergone many vicissitudes. After being left derelict in the late 19th century, a new canal system called the Wei-hui was opened in 1937.