Nyakchu or Nyachu, or Nyag River (Tib. ཉག་ཆུ་, Wyl. nyag chu), known as Yalong in Chinese, is the largest tributary of the Drichu (Yangzi Jiang in Chinese) which is 1,323km. It takes its source on the southern side of the Bayanhari Mount (Wyl. ba yan ha ri) in the Qinghai province before flowing towards the east through Tridu (Wyl. khri ’du), Sershul (Wyl. ser shul), Kardze (Wyl. dkar mdzes), Nyarong, "the valley of the Nyag river", and Nyakchuka, "mouth of the nyag river", and so on.