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.
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Extended data figures and tables
Extended Data Figures
- Extended Data Figure 1: Water stress. (726 KB)
Baseline water stress (total annual water withdrawals (municipal, industrial, and agricultural) as a percentage of the total annual available blue water) for the major HMA river basins in 201545. The dashed line represents the Line of Control in Jammu and Kashmir agreed on by India and Pakistan. The final status of Jammu and Kashmir has not yet been agreed on by the parties. IAK refers to Indian-administered Kashmir, PAK to Pakistan-administered Kashmir.
- Extended Data Figure 2: Inter-annual precipitation variability. (209 KB)
Annual relative precipitation variability (coefficient of variation normalized by mean, 1961–199025; colour scale) for the Aral (1), Indus (2), Brahmaputra (3), Ganges (4), Tarim (5), Issyk-Kul (6) and Balkhash (7) basins in the global context.
- Extended Data Figure 3: Relative inter-annual precipitation variability by basin. (420 KB)
a–g, Precipitation is shown relative to the mean (blue); ±1 coefficient of variation is indicated by the dashed grey lines. Relative interannual variability is lowest in the Brahmaputra (d) and Ganges basins (c), intermediate in the Indus (b) and highest in the four northern basins (a, e–g).
- Extended Data Figure 4: Datasets and processing flow used in this study. (270 KB)
Processing scheme to derive NMFs for each catchment. See Methods section ‘Data available’ for references.
- Extended Data Figure 5: Average- and drought-year monthly precipitation. (321 KB)
a–g, Monthly basin precipitation for an average year (green) and the driest year on record (blue) for the Aral (a), Indus (b), Ganges (c), Brahmaputra (d), Tarim (e), Issyk-Kul (f) and Balkhash (g) basins.
- Extended Data Figure 6: Definition of zones. (539 KB)
River-basin hypsometric zones 2–4 are defined12 as covering the area above the area-weighted mean glacier terminus height for each basin, plus the upper 75%, 50% or 25%, respectively, of the remaining basin area.