A review of isotope ecohydrology in the cold regions of Western China

The mountainous alpine area in western China is an Asian water tower and is an important ecological barrier area. Based on the previous research results, this study sorted out and summarized the isotopic ecohydrology of the alpine mountains in the western China and found that the local meteoric water line (LMWL) in the west of the alpine mountains is δD = 7.44δ18O + 5.23 (R2 = 0.86). The temperature effect showed an increasing trend from the south to north, while the precipitation effect showed an opposite direction. The water vapor sources in the western alpine mountains are complex. When the temperature coefficient is <0, the water vapor source is dominated by the southwest monsoon; when the temperature coefficient is 0-0.3, the water vapor source is jointly dominated by the southwest monsoon and the westerly wind; when the temperature coefficient is more significant than 0.3, the water vapor source is dominated by the westerly wind. Different water bodies are affected by water supply and evaporation differences. The altitude effect of δ18O value in precipitation in the western alpine mountains is -1.3 ‰/100 m, and the altitude effect of δ18O value in river water is -0.17 ‰/100 m. The primary source of plant water in the study area is soil water, and the utilization rate of water is closely related to plant types and the regional environment. Water vapor recycling has become an essential part of regional precipitation water vapor sources. However, with the deepening of the major national strategy of ecological civilization construction, the western alpine mountainous area are undergoing profound and drastic changes in the ecological and hydrological processes under the changing environment, which brings great challenges to regional water resources security, ecological security and sustainable development. In the future, the comprehensive innovations in observation, sampling, modeling and theory are urgently needed.