4.1 Impact of stable snow on hydrological processes
In this study, we investigated the process of stable snow formation and its distribution pattern in two major watersheds of the eastern Tibetan Plateau-Kawasaki Plateau by means of the daily MODIS snowpack dataset, showing that the distribution pattern of stable snow was different between the Mamukau River Basin in the hilly plateau region and the Hanliu River Basin in the alpine valley region; in the Mamukau River Basin, the area of stable snow cover was larger in the spring, and the area of stable snow cover was smaller in the winter. The long retention time of the spring snowpack, its ablation rate is much smaller than that in winter, and the large area of stable snowpack provides an adequate water supply for the downstream rivers, similar to the role of glaciers in recharging water resources in summer. It shows that the spring snowmelt can effectively regulate the downstream river runoff, and the water volume is more uniform; while the winter snow melt is fast, the downstream river may rise significantly in a short period of time, but the water volume fluctuates greatly, and the winter snowfall is small, which may lead to some of the rivers in winter with small water volume or ”cut-off”(López-Moreno et al. 2020); in the alpine valley area of the Hanliu River Basin, the stable snowpack is mainly distributed in the high altitude area, which is the main source of water supply. In the Hanliu River basin in the alpine valley area, the stable snowpack is mainly distributed in the high altitude areas. Due to the large vertical difference, there are differences in the water and heat conditions in different areas, and the melting of snow shows a situation of ”low first and then high”, with the snow at low altitude melting faster and the snow at middle and high altitudes melting later, which can play a role in regulating river runoff to a certain extent. In winter, due to less precipitation and faster ablation, this regulation may be less effective than in spring, and in the later stages there may be a significant reduction in the volume of water in the downstream rivers(Harpold et al. 2017).
Stable snowpack, as a stable material, is important for biochemical cycling at regional and hemispheric scales. In the snowy season, the stable snowpack can cache a large amount of snow, which makes the snow and ice gradually melt and infiltrate into the soil, providing a stable runoff supply for the snow melting season. Compared with the unstable snowpack, the snowmelt runoff in the stable snowpack area in the spring and summer snow melting seasons is more stable, which can effectively prevent the spring and summer ice and snow flood disasters, and is of great significance for the residents’ production and life and the water supply of the city, and other water resources management. In addition, stabilizing snowpack plays an important role in temperature regulation. Due to its high albedo, snow can effectively reflect solar radiation and reduce the ability of the ground to receive solar radiation. In this study, the snowpack on the Western Sichuan Plateau was studied and analyzed, and although the focus of this study was mainly on the Western Sichuan Plateau, it is representative and exemplary as part of the Tibetan Plateau. At the same time, snowpack, as one of the important elements on a global scale, has a significant impact on climate change and water allocation(Sturm et al. 2005). In-depth study of the formation process and pattern of stable snowpack on the western Sichuan Plateau can provide reference value for the study of stable snowpack in other highland mountain areas and contribute to the understanding of global stable snowpack. In addition, the study of the formation process and stabilization pattern of the stable snowpack in the Western Sichuan Plateau can provide insights into ecological environmental protection, water resource management and disaster prevention on a global scale, which is of great significance in promoting scientific research and practice in this field.