Sumdorong Chu is a tributary of the Nyamjang Chu river that flows along the disputed Sino-Indian border between the Tsona County of Tibet and the Tawang district of Arunachal Pradesh. It originates in the Tokpo Shiri Glacier, about 7–10 kilometres east of Nyamjang Chu, and flows down to the river. Its junction with Nyamjang Chu is to the north of that of Namka Chu, another contested river valley, by about two kilometers.

Namka Chu or Kejielang River is a tributary of Nyamjang Chu that flows along the disputed border between India and China. The Indian side of the border is the Tawang district in Arunachal Pradesh. The Tibetan side of the border is in Tsona Dzong, Shannan province of Tibet. Namka Chu originates near the trijunction of Tibet, Bhutan and India and flows east for 26 km before joining Nyamjang Chu. It is about 200 kilometers away from the Misamari railhead and 60 kilometers from the Tawang road head. The Namka Chu valley was the scene of some of the most fierce fighting between India and China during the 1962 Sino-Indian war.