Arid and semiarid regions account for ~ 40% of the world’s land area. Rivers and lakes in these regions provide sparse, but valuable, water resources for the fragile environments; and play a vital role in the development and sustainability of local societies. During the late 1980s, the climate of arid and semiarid northwest China dramatically changed from “warm-dry” to “warm-wet”. Understanding how these environmental changes and anthropogenic activities affect water quantity and quality is critically important for protecting the aquatic ecosystem and determining the best use of freshwater resources. Lake Bosten is the largest inland freshwater lake in NW China and has experienced inter-conversion processes between freshwater and brackish status. Herein, we explored the long-term water level and salinity trends in Lake Bosten from 1958 to 2019. During the past 62 years, Lake Bosten’s water level and salinity exhibited “W” and “M” patterns. Partial least squares path modeling (PLS-PM) suggested that the decreasing water level and salinization during 1958–1986 were mainly caused by anthropogenic activities, while the variations in water level and salinity during 1987–2019 were mainly affected by climate change. The transformation of anthropogenic activities and climate change is beneficial for sustainable freshwater management in Lake Bosten Catchment. Our findings highlight the benefit of monitoring aquatic environmental changes in arid and semi-arid regions over the long-term for the purpose of fostering a balance between socioeconomic development and ecological protection of the lake environment.

The analysis of stable isotope composition is an important tool in research on plant physiological ecology. However, large-scale patterns of leaf stable isotopes for aquatic macrophytes have received considerably less attention. In this study, we examined the spatial pattern of the leaf δ13C and δ15N of macrophytes collected across the arid zone of northwestern China and tried to illustrate how they were affected by different environmental factors. Our results showed that the mean values of leaf δ13C and δ15N in the macrophytes sampled from the arid zone were -24.49‰ and 6.82‰, respectively, which were drastically higher than the values of terrestrial plants. In addition, leaf δ13C varied significantly among different life forms, possibly reflecting the complex photosynthetic fixation and adaptations of macrophytes. In addition to, our studies indicated that the foliar δ13C values of all the aquatic macrophytes were only negatively associated with precipitation, but the foliar δ15N values were mainly associated with temperature, precipitation and potential evapotranspiration. Therefore, we speculated that the determinant of the leaf δ13C of macrophytes in the arid zone of northwestern China is water factors and the leaf δ15N values is the complex combination of water and energy factors.