Datong River, also known as Haomen River, is a first-class tributary of Huangshui River system in the Yellow River Basin. It originated in Namujimuling, Shaguolin, between Tuolai Nanshan and Datong Mountain in the east of Qilian Mountain. It flows through Gangcha, Qilian and Haiyan counties in Qinghai from northwest to southeast, enters Gansu at Tang Tian Temple in Tianzhu County, Gansu Province, passes through Yongdeng and Honggu counties in Lanzhou, and then flows into Xiangtang Town, Minhe County, Qinghai Province, where it flows into Huangshui River. The length of the main stream is 574. 12km, and the drainage area is 15 133km2. Among them, the length in Gansu is 109.7km, and the drainage area is 2 190km2. The annual average runoff of Liancheng Station of Datong River is 2.82 billion cubic meters, the annual average runoff is 2.93 billion cubic meters (xiang tang Hydrological Station), and the total self-produced water resources is 280 million cubic meters.
Huangshui is a large general tributary in the upper reaches of the Yellow River, located between Datong Mountain, Daban Mountain and Laji Mountain. Originated in Baohutu Mountain, Haiyan County. The southeast flows to the southeast, flows out of the province in Shahewan Village, Minhe County, and joins the Yellow River in Dachuan, Gansu Province. The main stream has successively passed through Haiyan, Huangyuan, Huangzhong, Xining, Huzhu, Ping 'an, Ledu and Minhe in Qinghai. Huangshui River mainstream 373. 9 kilometers long, including 335. Qinghai is 4 kilometers. Watershed area 16 120 km2 (excluding Datong River). The average discharge of Huangshui Minhe (II) Hydrological Station for many years is 56. 8 cubic meters per second.
The source of Huangshui River is called Baohutu River, also called Mapisi River, which originated from the western end of Baohutu Mountain. It flows southeast along the foot of Baohutu Mountain, turns southeast through Haiyan County, and flows into Dongdatan Reservoir after meeting the Halijian River. The river channel in this section is wide, the riverbed is generally tens of meters, the river is clear, and the main stream and tributaries at all levels form a dendritic water system. After leaving Dongdatan Reservoir, it enters Huangyuan Basin through Bayan Gorge, turns southeast near Huangyuan County, flows through Zhamalong Gorge, enters Xining Basin, and then passes through Xiao Xia to 3. 6 kilometers below Liucun Bay, Ledu County. The wide valley of this section of the river is the same as the canyon, and the wide valley is the main one. Generally, the riverbed in the wide valley is 100-200m wide, the widest is about 300m near Xining, and the canyon zone is only 30-50m.