Changes in Glaciers and Their Runoff in the Shule River Basin of the Qilian Mountains from 1980 to 2100 Based on Remote Sensing Data and Modeling

Glaciers are vital freshwater resources in some arid regions, where glacier meltwater sustains downstream ecosystems, land-use activities and regional water security. However, systematic investigations of long-term glacier change and its hydrological implications remain limited in the Shule River Basin (SRB) of the Qilian Mountains, China. Our study quantified spatiotemporal glacier changes and their meltwater in the SRB from 1980 to 2100 by integrating Landsat imagery, digital elevation models, meteorological and hydrological data, existing glacier datasets and modeling. In 2025, 627 glaciers covering ~437.75 ± 35.46 km2 were identified in the SRB, representing a shrinkage of 213.2 km2 (mean 4.74 km2 a−1) from 1980 to 2025. The glacier surface elevation change rate reached −0.60 m a−1 during 2000–2014, with accelerated thinning after 2010. The mean glacier mass balance was −343.63 mm w.e. a−1 during 1970–2023 and glacier meltwater contributed an average of 25.1% to basin runoff during 2008–2021, peaking at 36.71% in 2011. Future projections under the SSP-119, SSP-245 and SSP-585 scenarios indicate continued glacier retreat, with peak glacier meltwater expected between 2024 and 2045. These findings highlight the declining hydrological regulatory capacity of glaciers and provide scientific support for sustainable land–water management and ecosystem resilience in glacier-fed arid basins.