Dangqu

The Dangqu, Dam Qu (Chinese: 当曲, p Dāngqū) or Dam Chu (Tibetan: འདམ་ཆུ, w 'Dam Chu, lit. "Marshy River") is the longest source of the Yangtze River, with a total length of 365.7 km (227.2 mi) located in the Qinghai province of the People's Republic of China. It runs from its source in an eastern offshoot of the Tanggula Mountains (唐古拉山), receives its main tributary the Buqu-Gar Qu River (布曲), and has a confluence with the Ulan Moron, where the Tongtian River is formed. The Dangqu has been discovered to be the actual and the longest headwater of the Yangtze River under modern criteria, although the nearby Ulan Moron or Tuotuo was traditionally regarded as the primary river of the two.^[1]

Dam Qu
The headwaters of the Yangtze, including the Ulan Moron ("Tuotuo"), Dangqu, Buqu, and Garqu.
Location
Country	China
Physical characteristics
Source	Tanggula Mountains
• location	Jari Mountain
• elevation	5,308 m (17,415 ft)
Mouth	Tongtian River to a confluence with Tuotuo River
Length	365.7 km (227.2 mi)
Basin size	30,540 km2 (11,790 sq mi)
Discharge
• average	2,571 m3/s (90,800 cu ft/s)
Basin features
Tributaries
• left	Bu Qu River Gar Qu River Za'Gya Zangbo

Moron Us

Traditionally, the Dangqu—sometimes under the name Akdam, Akedamuqu, or A-ko-ta-mu-ch'ü—and the Buqu were both regarded as tributaries of the Garqu (尕尔曲), then known as the Moron Us (Mongolian: Mörön Us or Маруй-Ус, Maruy-Us; 木鲁乌苏河, p Muluwusu He) or Dequ (Дечу, Deču). Under modern criteria, the Garqu is instead considered to be a tributary of the Buqu.