Lake located at 5030 m above mean sea level on the southern Tibetan Plateau. It is 32 km long, 14 km wide, and covers an area of 280 sq.km. Streams of water from the snow-capped surrounding mountains feed the lake.

Puma Yum literally means The Blue Jewel which is floating in the sky. The lake freezes in winter and is crossed by shepherds with their sheep. Since the climate is warming, the ice is becoming thinner and thus creates a problem for the 120 people living off and around the lake.

The lake is considered ultraoligotrophic, meaning that nutrient concentrations in both the water column and lake sediments are extremely low. Water in such lakes tends to be blue to blue-green and to have high clarity due to low levels of photosynthesizing organisms such as phytoplankton.

During the winter, the lake develops intricate ice block patterns on the surface, ranging from ten to hundreds of metres in diameter. The ice pattern is caused by repeated cycles of freezing, fracturing, and refreezing of the ice due to variations in temperature and wind-induced ice motion.