Reduced Future Summer Water Availability in the Tien Shan Due To Glacier Wastage

Abstract Glaciers in the Tien Shan mountains of Central Asia are a crucial source of freshwater for agriculture and local communities, sustaining over 100 million people in the region. Here, we project future water availability for this region by dynamically modeling the evolution of all glaciers and merging their runoff with hydrological runoff simulations from three global hydrological models. We compare this hybrid estimate of water availability with water demand simulations to assess potential risks of water scarcity. Our findings show that Tien Shan glaciers are projected to lose around one‐third of their 2020 ice mass before 2040, and between 69% and 93% by 2100, depending on the climate scenario. Compared to a 2000–2020 baseline, the runoff from glacier areas initially increases by 15%–24%, reaching its peak before 2050, followed by a decrease of 14%–20% by 2100. This reduction is particularly pronounced in summer, when glacier areas currently supply up to 45% of total summer runoff, coinciding with peak water demand. A gradual shift in glacier‐area runoff toward spring further intensifies the risk of summer water shortages. By the late 21st century, the probability of unmet water demand in summer is projected to increase significantly, especially in heavily glaciated basins, where the increase ranges from 30% to 70% depending on the emissions scenario. These findings highlight the urgent need for adaptive water management strategies and climate mitigation efforts to preserve long‐term water security for millions of people reliant on glacier‐fed rivers for their water supply.