The Wei River () is a major river in west-central China's Gansu and Shaanxi provinces. It is the largest tributary of the Yellow River and very important in the early development of Chinese civilization. The source of the Wei River is close to Weiyuan CountyWei yuan meaning "Wei's source"in Gansu province, less than from the Yellow River at Lanzhou. However, due to the sharp turn north the Yellow River takes in Lanzhou, the Wei and the Yellow River do not meet for more than further along the Yellow River's course. In a direct line, the Wei's source lies west of the main city along its course, Xi'an in Shaanxi province. The length of the river is and the area drained covers . The Wei River's tributaries include the Luo River, Jing River, Niutou River, Feng River and the Chishui River. The Wei River valley has a continental climate, with hot summers and cool, dry winters. It sits between the arid steppes and deserts to the north and the forests of the Qingling mountains. Its natural vegetation would be a steppe-forest, but it has been transformed by human activity and is mostly agricultural. History In Chinese mythology, the giant Kua Fu drained the Yellow River and the Wei River to quench his burning thirst as he pursued the Sun. The valley of the Wei was one of the early cradles of Chinese civilization, along which the capitals of the Zhou, Qin, Han, and Tang dynasties were situated. The area of Dingxi around its headwaters in Gansu has numerous Stone Age sites from various early cultures. The Wei Valley is likely the earliest center of Chinese civilization, and also the location of China's first major irrigation works. Some Chinese historians now believe the Wei is the ancient Jiang River that gave its name to the families of Shennong and the Yan emperor, two Chinese legendary heroes credited with the early development of agriculture there. As "China's natural gateway" to the west, the headwaters of the Wei River are also notable in the development of the Northern Silk Road. The Chinese segment of the Northern Silk Road connected Chang'an (then the capital of China) to the west via Baoji, Tianshui at the Wei's headwaters, Lanzhou, Dunhuang, and the Wushao Ling Mountain, before looping north of the Taklamakan on its way to Kashgar and the routes into Parthia. The Wei River Bridge (Weihe Qiao