It is a barrier lake due to landslide or debris flow jams river as natural damming. The narrowest point of the lake is less than 1 kilometer. There are many barrier lakes in southeast Tibet as valleys are blocked by glacial till.
Ranwu Lake is next to the Sichuan–Tibet Highway and is a popular stopping point for tourists who are on that highway.
The mainly supply of water for Ranwu Lake is melt water from the snowy mountains and glacier around the lake. The lake water runs to the west as the source of Parlung Zangbo, an important tributary of Yarlung Zangbo River.
With enough supply water, Ranwu Lake is a freshwater lake. The water’s temperature is low, ranging form 6.6°C to 15.4°C (44 to 60°F) in summer, and it is frozen in winter.
The lake teems with hillstream loach and you can taste the tender fishes at small eateries on both sides of the road near the lake.
Scenery: Ranwu Lake is quiet and blue with few dead branches. There is verdant grassland and plants by the blue lake in harmony with snowy mountains. The color of the water varies with the seasons.
The lake is covered with tree shadows in spring and summer, and mist in fall and winter makes it as a dreamland.