Why is water transportation on the upper Mekong River mostly local?

Water transportation on the upper Mekong River is primarily limited to local traffic due to the river's challenging physical geography. In its upper reaches, the Mekong cuts deeply into a rugged, mountainous landscape, creating a long, narrow valley that is often remote and sparsely populated.12

Furthermore, the river's course through the highlands of Tibet and Yunnan is characterized by steep terrain and difficult accessibility, which restricts large-scale navigation. While continuous water transport on the river as a whole is also hindered by major physical barriers such as the Khone Falls, the specific constraints of the upper section are defined by its deep, rugged streambed and the remote nature of the surrounding highlands.123