The Wei River (Chinese: 渭河; pinyin: Wèi Hé; Wade–Giles: Wei Ho) 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. In ancient times, such as in the Records of the Grand Historian, the river was called Wei Shui (渭水; Wèishuǐ; 'Wei water').
The total length of the Wei River is 818 km (508 mi), covering a drainage area of 135,000 km2 (52,000 sq mi). Some of the major tributaries include the Luo River, Jing River, Niutou River, Feng River and the Chishui River. In a direct line, it travels due east for 700 km (430 mi) before draining into the Yellow River at Tongguan County near the tri-provincial boundary between Shaanxi, Shanxi and Henan provinces, with a series of major cities along its course including Tianshui, Baoji, Xianyang, Xi'an and Weinan.
Course
The source of the Wei River starts in the mountainous region in southern Weiyuan County (literally meaning "Wei's source"), Gansu province, with the westernmost headwater of its mainstem Qingyuan River (清源河) less than 1.6 km (0.99 mi) away from a headwater of Manba River, a main tributary of the Tao River, which is the second-largest tributary of the Yellow River (behind the Wei River itself). The head of the Wei River proper — formed by confluence of the Qingyuan River with two small tributaries to its northwest — is less than 110 km (68 mi) from the Yellow River at Lanzhou, but due to the sharp north turn the Yellow River takes in Lanzhou to form the Ordos Loop, the Wei and the Yellow River do not meet for more than 2,000 km (1,200 mi) further along the Yellow River's course.
After being joined by numerous other tributaries just east of the Weiyuan County town center, the Wei River turns slightly southeast until it reaches Wushan County, continuing east for 20 km (12 mi) before turning slightly southeast again at Gangu County and curves north of Tianshui, the second-largest city of Gansu. After picking up the Ji River (耤河, the urban river of Tianshui) east of the city, the Wei River enters the Mount Long and emerges to become the principal river in the Guanzhong Basin. It drains into the Yellow River south of the boundary between Dali County and Tongguan County, just as the Yellow River bends sharply east to enter the North China Plain.
