Glacier Coverage Dominates the Response of Runoff and Its Components to Climate Change in the Tianshan Mountains

In the context of climate warming, runoff changes in the Tianshan Mountains vary widely across basins, with both increasing and decreasing trends. However, the underlying mechanisms remain to be elucidated due to the complexity of the response of runoff components (rainfall runoff, snowmelt runoff, and glacier runoff) to climate change. Here, we quantified the effects of historical (1982–2015) precipitation and temperature changes on runoff and its components and projected future (2016–2100) runoff changes in 25 basins with diverse glacier coverage in the Tianshan Mountains. A multivariate calibration scheme was used to constrain the hydrologic model to generate reasonable runoff component partitioning. Our results indicate that historical runoff responses to changes in precipitation and temperature are highly correlated with the extent of glacier coverage at the basin scale. Future runoff trends in highly and moderately glacierized basins depend largely on the magnitude of warming: tending to decrease under the low warming scenario and increase under the high warming scenario. In contrast, runoff in low glacierized basins is expected to increase due to increased precipitation. Moreover, the contribution of R_glacier to runoff is projected to be negligible (<5%) in most moderately and low glacierized basins by the end of this century (2071–2100), posing a challenge to the stability of regional water supplies.