Ranwu Lake is the main supply of Palong Tsangpo, a branch of The Yalu Tsangpo River. The lake has an area of 22,000 square kilometers, at an altitude of 3,850 meters, with length 26 km and width 1 to 5 km. In the north, it is the famous Lagu glacier, extending to the lake. Every time the ice melts, the water flows into the river, keeping the lake water abundant. Southeast is the Gangri Garpo, Ahzhagongla glacier in the south and Boshula Mountains in the northeast. Thawed snow is the cause of the Palong Tsangpo river (a branch of The Yalu Tsangpo River) with rocks and small islands in the river. By the lake are the verdant grassland and plants in harmony with the blue lake and snowy mountains. The narrow Arm-tso Lake winds its way about ten thousand miles westward into a valley. The lake water appears different colors in different seasons, from aquamarine to turquoise.