The HKH region extends 3,500 km over all or part of eight countries from Afghanistan in the west to Myanmar in the east. It is the source of ten large Asian river systems – the Amu Darya, Indus, Ganges, Brahmaputra (Yarlungtsanpo), Irrawaddy, Salween (Nu), Mekong (Lancang), Yangtse (Jinsha), Yellow River (Huanghe), and Tarim (Dayan) – and provides water, ecosystem services, and the basis for livelihoods to a population of around 240 million people in the region. The basins of these rivers provide water to 1.9 billion people, a fourth of the world’s population.
A considerable volume of water resources is stored as snow and glacier ice in the HKH. Cryosphere components including permafrost and glacial lakes provide various ecosystem services for mountain and downstream communities. The snow cover area during winter varies between 951,000 sq km and 1,390,000 sq km. During summer, it ranges between 388,000 and 481,000 sq km The total glacier area can extend up to 87,340 sq km.