Asia’s glaciers are a regionally important buffer against drought

The high mountains of Asia—encompassing the Himalayas, the Hindu Kush, Karakoram, Pamir Alai, Kunlun Shan, and Tian Shan mountains—have the highest concentration of glaciers globally, and 800 million people depend in part on meltwater from them. Water stress makes this region vulnerable economically and socially to drought, but glaciers are a uniquely drought-resilient source of water. Here I show that these glaciers provide summer meltwater to rivers and aquifers that is sufficient for the basic needs of 136 million people, or most of the annual municipal and industrial needs of Pakistan, Tajikistan, Turkmenistan, Uzbekistan and Kyrgyzstan. During drought summers, meltwater dominates water inputs to the upper Indus and Aral river basins. Uncertainties in mountain precipitation are poorly known, but, given the magnitude of this water supply, predicted glacier loss would add considerably to drought-related water stress. Such additional water stress increases the risk of social instability, conflict and sudden, uncontrolled population migrations triggered by water scarcity, which is already associated with the large and rapidly growing populations and hydro-economies of these basins. Glaciers in the high mountains of Asia provide a uniquely drought-resilient source of water, supplying summer meltwater sufficient for the basic needs of 136 million people. Glacial thirst quenchers Glaciers are often considered as valuable, but not critical, contributors to water supply. But Hamish Pritchard now shows that glaciers are a key source of water for much of the high-mountain region of Asia. Estimates of relevant quantities such as mountain precipitation have uncertainties that are difficult to quantify, but the author's findings suggest that some basins, including the Aral and Indus, which have a combined population of over 360 million, are dominated by glacially sourced water contributions during drought years. Extensive glacier loss, which may occur in a warming climate, could therefore exacerbate water stresses in an already heavily taxed system.