The Mekong valley (Dza chu) starts from Lungmug pass up to the sea passing Chamdo.
For Tibetans, the Dza chu divided in 2 branchs: the white and the black called respectively Dzakar chu and Dzanak chu.
The traditional North-West branch (Dzanak chu), best known and located near the Lungmug Pass road is 87.75km long.
The North branch (Dzakar chu) comes from a large north mountain range. At the foot of the mountain, it shares into 2 parts 91,12 km and 89,76 km in lenght.
In his book, "The last Barbarians" (published by Henry Holt, New York, 1997), Michel Peissel gives a description of the traditional source.
Several Japonese expeditions are presently on the ground to make pictures of the north branchs.
The Chinese Academy of Science had agree that the north branch seems to be the longest river and the true Mekong headwater as it is physically the case when we examine the satellite pictures.