Abstract:

In recent years, the speed of snow melting has accelerated due to climate change. Thus, the frequency and intensity of extreme hydrological events have also increased, and the Ili River Valley has become a high-incidence area in Xinjiang, China for spring snow-melting floods. This study attempts to analyze the dynamic process of snow melting, the characteristics of the change in water and heat in frozen soil and its response to temperature, and the amount of snow melting that occurs in a short time scale during the whole year’s snow cover period by using the observed data regarding the soil temperature, humidity, and snow melting in the Araltobe watershed near the Tianshan Station for Snow Cover and Avalanche Research of the Chinese Academy of Sciences. The results show that the snow melting in mountain areas can be divided into three stages, namely, the complete ablation stage, the incomplete melting stage, and the complete ablation stage. During the frozen soil thawing stage, the change in the soil temperature depends on the atmospheric temperature, and the soil moisture is highly correlated with the snow melting and temperature. The change in the soil moisture content is greater in the surface layer, whereas it remains relatively stable in the deep layer. The seasonal change of soil temperature and humidity from autumn to winter to spring generally follows a “descending, stabilizing, and rising” trend. In the upper layer of the frozen soil, the soil water content increases with the increase of the snow melting until it reaches the saturation value, whereas in the lower boundary (40 cm) of the frozen soil, the soil water content does not increase with the continuous increase of the accumulated snowmelt, but rather, it maintains a stable unsaturated water content, which indicates that the soil flow occurs in the shallow surface layer (0-40 cm) after the snowmelt water infiltrates into the soil. Additionally, the results show that snowfall is the main source of water resources. The amount of snowmelt is significantly correlated with temperature (the correlation coefficient is 0.785), and the rate of the contribution of the snowmelt to the formation of the water resources is about 40%. The study of the response process of the frozen soil hydrothermal to the snowmelt and temperature is of important reference value in the formation mechanism of water resources and in the transformation and utilization of flood forecasting in Xinjiang.

Key words: seasonal frozen soil, soil temperature and humidity, snow water equivalent, air temperature, freeze-thaw process