Hydrological responses to climate warming for mountainous regions in the northeastern Tibetan Plateau

The Tibetan Plateau (TP), often referred to as the “Asian Water Tower,” hosts extensive cryospheric resources that are highly sensitive to climate warming. The Qilian Mountains (QL), located in the northeastern TP, constitute a key ecological security barrier in western China and a strategic corridor of the Silk Road Economic Belt. Based on multi-source datasets and the runoff coefficient method, we estimate the mean annual runoff of the Qilian Mountains to be approximately 15.671 billion m³. River basins originating in the eastern Qilian Mountains exhibit a clear declining trend in annual runoff, whereas most basins in the central and western regions show increasing trends, suggesting that sustainable water resource development in the eastern Qilian Mountains faces greater challenges under continued warming.

Thus, we chose the Beichuan River Basin which is located in the eastern Qilian Mountains as the study area. A snowmelt pathway-tracking algorithm and a reservoir operation scheme were integrated into a high-resolution, physically based distributed hydrological model (DHSVM) to investigate the mechanisms of runoff generation. The results indicate that both the annual snow contribution to soil moisture (SC-SM) and the snow contribution to streamflow (SC-S) declined significantly from 1965 to 2019. At the monthly scale, SC-SM exhibited the largest amplitudes in the upper soil layer, while peak contributions in deeper layers lagged behind those of the shallow layer. In addition, mean monthly SC-S across all stations displayed a distinct bimodal pattern associated with the seasonal snowfall regime. Reservoir regulation measures only exerted minimal impacts (≤2.0 %) on SC-S. Furthermore, based on long-term meteorological observations, we analyzed the spatiotemporal variability of the temperature lapse rate and its associated hydrological responses.