Future snow changes and their impact on the upstream runoff in Salween

Abstract

Abstract. Understanding the hydrological processes related to snow in global mountainous regions under climate change is necessary for achieving regional water and food security (e.g., the United Nation's Sustainable Development Goals 2 and 6). However, the impacts of future snow changes on the hydrological processes in the high mountains of the “Third Pole” are still largely unclear. In this study, we aimed to project future snow changes and their impacts on hydrology in the upstream region of the Salween River (USR) under two shared socioeconomic pathway (SSP) scenarios (SSP126 and SSP585) using a physically based cryosphere–hydrology model. We found that the climate would become warmer (0.2 ∘C per decade under SSP126 and 0.7 ∘C per decade under SSP585) and wetter (5 mm per decade under SPP126 and 27.8 mm per decade under SSP585) in the USR in the future under these two SSPs. In this context, the snowfall, snow cover, snow water equivalent, and snowmelt runoff are projected to exhibit significant decreasing trends during 1995–2100, and the decreases are projected to be most prominent in summer and autumn. The future (2021–2100) snowmelt runoff is projected to significantly increase in spring compared with the reference period (1995–2014), which would benefit the availability of water resources in the growing season. The annual total runoff would significantly increase in all of the future periods due to increased rainfall, which would increase the availability of water resources within the basin, but the high peak flow that occurs in summer may cause rain flooding with short duration and high intensity. Compared with the reference period (the contribution of snowmelt runoff to the total runoff was determined to be 17.5 %), the rain- and snow-dominated pattern of runoff would shift to a rain-dominated pattern after the near term (2021–2040) under SSP585, whereas it would remain largely unchanged under SSP126. Climate change would mainly change the pattern of the snowmelt runoff, but it would not change the annual hydrograph pattern (dominated by increased rainfall). These findings improve our understanding of the responses of cryosphere–hydrological processes under climate change, providing valuable information for integrated water resource management, natural disaster prevention, and ecological environmental protection at the Third Pole.

Hydrological Projections in the Third Pole Using Artificial Intelligence and an Observation‐Constrained Cryosphere‐Hydrology Model

“…Over its extensive development history, the WEB‐DHM has consistently demonstrated its reliability in describing cryosphere‐hydrological processes in alpine glacier regions. It has generated dependable, high‐precision runoff and ET data for the seven major rivers in the TP, forming crucial inputs for this study (Chai et al., 2022; H. Liu et al., 2023; J. Qi et al., 2019; W. Qi et al., 2022; L. Song et al., 2020; J. Zhou et al., 2022).…”

Tibetan Plateau Runoff and Evapotranspiration Dataset by an observation-constrained cryosphere-hydrology model

“…A suite of metrics was utilized to assess the performance of the model and reliability of various products; these included the Nash coefficient 70 , Bias, Root Mean Square Error ( RMSE ), and Correlation Coefficient ( CC ) 71 . These metrics are computed as follows: here, represents the reference value at the i moment, such as observed flow or ET calculated using the water balance method; X is the target variable being evaluated, and n is the number of samples; and represent the mean values of the reference sequence and target sequence , respectively.…”

Large-scale circulation dominated precipitation variation and its effect on potential water availability across the Tibetan Plateau

“…Based on the significantly positive correlation between precipitation and runoff, we examine the influence of ISM characteristics on potential water availability, mirrored in the runoff (Wang et al 2021b). With the help of simulations from the hydrological models around the southeastern TP (Qi et al 2019, Wang et al 2021c, Chai et al 2022, the surface runoff from ERA5-Land is firstly evaluated. A comparable and similar distribution of surface runoff is found between ERA-Land and simulations (figure A4), with maximum in the downstream of Brahmaputra River and Ganges river and smaller values in the upper Yellow river and upper Yangtze river basins.…”