<P> 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 . </P> <P> The source of the Wei River is close to Weiyuan County--Wei yuan meaning "Wei's source"--in Gansu province, less than 200 kilometres (120 mi) 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 2,000 kilometres (1,200 mi) further along the Yellow River's course . In a direct line, the Wei's source lies 700 kilometres (430 mi) west of the main city along its course, Xi'an in Shaanxi province . The length of the river is 818 kilometres (508 mi) and the area drained covers 135,000 square kilometres (52,000 sq mi). </P>

Which river is important in the development of chinese civilization