In arid areas，snowmelt is the main source of water resource formation. Therefore, the formation, transformation and utilization of snow resources are important research topics on the development and utilization of water resources in Xinjiang, China. Further, hydrological model is a key to determine the formation and transformation of water resources. This study uses the field experimental area of Tianshan Snow Station, Chinese Academy of Sciences, as the experimental area. The meteorological data and snowmelt amount were adopted as the independent and dependent variables. A snowmelt model based on temperature change is studied, and a single-factor simple model is calibrated and validated. Simultaneously, the variation law of snowmelt in the experimental area for many years and the response process of snowmelt to temperature are analyzed. The results indicate that snowmelt still occurs in winter in certain low-temperature ranges. In the study area of Tianshan Mountains, the critical value of daily average temperature of snowmelt is approximately -7 ℃. When the temperature is lower than -7 ℃, snowmelt is basically suspended, reflecting the characteristics of snowmelt in arid areas. In terms of the model, a single factor simple snowmelt model based on temperature exhibits good performance in simulating snowmelt in mountainous areas. During the calibration period (2016—2020), the correlation parameters of Bias, MAE, RMSE, NSE and R² between the observed and simulated snowmelt values were -0.037, 0.367, 0.482, 0.870, and 0.876 respectively. The values of validation period were -0.210, 0.292, 0.577, 0.845, and 0.811, respectively. The simulation results and correlation coefficients during the validation period indicate that the simulated value of the model has good consistency with the measured value. The advantage is that the amount of snowmelt in the basin can be estimated through the available meteorological data. The results provide a relatively simple algorithm for snowmelt calculation in arid areas and a simple and effective snowmelt submodule for a hydrological model. This study has an important reference value for understanding the change law of snowmelt and the simulation and prediction of snowmelt runoff in subsequent studies.

Based on the runoff data and meteorological data of Laohugou watershed in the western of Qilian Mountains, northwest China, the research analyzed the relationship between runoff and meteorological variables in glacier area, and established a multivariate exponential nonlinear regression to reconstructe the runoff. In addition, the characteristics of interannual, seasonal, diurnal variations of runoff in the glacial region were analyzed. The results showed that: (1) The correlation between runoff and temperature is the highest (0.86), followed by water vapor pressure (0.81), relative humidity (0.46), and precipitation (0.27). Runoff is most affected by temperature. (2) The mean daily runoff is 2.10 m³·s^-1 in this century, which is higher than 1.65 m³·s^-1 in the late 1950s, the main reason is that the temperature increased by 0.75 ℃ in the ablation season. The interannual variation of runoff is large in the strong ablation period, and the interannual variation is small in the beginning (May-June) and end (September) of the ablation period. The proportion of runoff generation from May to September was 5.3%, 16.1%, 37.3%, 35.1% and 6.2%, respectively. (3) Multivariate exponential nonlinear regression equation can better simulate the daily runoff (the mean Nash efficiency coefficient is 0.70). After the supplement of the missing runoff, the diurnal variation of runoff is small in the beginning and end of the ablation period, but the diurnal variation of runoff is large in the strong ablation period. For the time-lag effect of runoff, monthly runoff in Laohugou watershed showed a characteristic of diurnal variation of “valley-peak” during the ablation period. The time interval between the maximum temperature and the maximum runoff was long in the beginning and end of the ablation period, while the time interval was short between the maximum temperature and the maximum runoff during the strong ablation period, and the maximum difference between the maximum temperature and the maximum runoff was 3 hours in June.

The Mongolian Plateau is a sensitive area for coping with global changes. It is also the only place for three of the nine routes of migratory birds. Lakes play the role of “indicator” and “life posthouse” in the plateau ecological environment. Relatively few research results have been presented on the changes of lakes in the Mongolian Plateau at home and abroad. Most of them focused on the analysis of typical and large lakes. Research on their causes has focused on meteorological and human factors, while that on small lakes and the relationship between the lake area and the soil environmental factors are relatively weak. Based on the Landsat remote sensing imagery, the information of the lake area above 1 km² per year on the Mongolian Plateau from 2000 to 2020 was extracted by the MNDWI water body index. The results of the temporal and spatial change characteristic analysis of the lake area showed that: (1) The area and the number of lakes have decreasing and increasing trends before and after 2009, respectively. Overall, the area and the number of lakes depicted a decreasing trend from 2000 to 2020. (2) The changes of lakes of different grades were quite different. The changes of the super large- and medium-sized lakes were relatively stable. Furthermore, the large-sized lakes showed the largest reduction. (3) The changes of the lakes in different regions also differed. These changes in the northwest were relatively stable, while those in the central and eastern regions were more dramatic. (4) Before 2009, the number of lakes in the dense areas in the central and eastern regions decreased, resulting in the weakening of the spatial distribution agglomeration of lakes in the study area. After 2009, the newly added lakes in the sparse area in the central region were scattered, weakening their spatial distribution agglomeration. (5) The correlation between the lake area and the annual average temperature, annual precipitation, annual evaporation, vegetation index, and four layers of soil moisture was relatively significant. The degree of influence exhibited in the two time periods significantly differed. Mastering the temporal and spatial changes of the lake in the Mongolian Plateau and their causes can provide a reference for the climate regulation, biodiversity protection, and climate disaster reduction research in the Mongolian Plateau and the whole world.

Groundwater is important for regulating the water cycle and ecosystem in arid areas. Understanding and managing groundwater resources is the key to preventing the reduction of river baseflow, ground subsidence and water quality degradation. Therefore, this study analyzed the groundwater chemical parameters and hydrogen-oxygen stable isotope characteristics of the Ebinur Lake Basin, Xinjiang, China, and explored the sources of groundwater recharge, dynamic changes of water chemical components in different regions by combining linear regression, two-terminal mixed model and GIS spatial analysis. The results showed that: (1) Different circulation processes of groundwater existed in different areas of the Ebinur Lake Basin, with the largest of hydrogen and oxygen isotopes (δ²H and δ¹⁸O) in the middle and lower reaches of the Bortala and Jing Rivers, followed by the area around Lake Ebinur Basin, and the smallest in the upper Bortala River area. (2) Deuterium excess parameter (d-excess) parameter and hydrochemical composition of groundwater reflected different groundwater recharge mechanisms and influencing factors. Groundwater in the upper Bortala River area was mainly recharged by glacial snow melt water. The main sources of groundwater in the middle and lower reaches of the Bortala and Jing Rivers were surface water and precipitation, which were also greatly influenced by the nature of rock formations, farmland development and irrigation measures. Groundwater around Lake Ebinur Basin mainly came from snow and ice melt and precipitation. The middle and lower reaches and groundwater in the river and lake confluence areas are the key areas for pollution prevention and control and management. (3) Different hydraulic connections existed in underground aquifers. The electrical conductance (EC) of flow system I ranged from 210.00 μS·cm^-1 to 2500.00 μS·cm^-1, and the d-excess ranged from 6.47‰ to 9.70‰. The EC of flow system II ranged from 141.60 μS·cm^-1 to 5260.00 μS·cm^-1, and the d-excess ranged from 9.61‰ to 17.45‰. In conclusion, this study investigated the driving mechanisms of hydrogen and oxygen isotopes and water chemistry in groundwater in the Lake Ebinur Basin, which provided some theoretical reference for the rational use and scientific development of groundwater resources in the basin.