Assessment of streamwater age using water stable isotopes in a headwater catchment of the central Tibetan Plateau

作者：Wang, Shaoyong; He, Xiaobo^*; Kang, Shichang; Hong, Xiaofeng; Fu, Hui; Xue, Yuang; Feng, Zijing; Guo, Haonan

来源：Journal of Hydrology, 2023, 618: 129175.

DOI：10.1016/j.jhydrol.2023.129175

• Tibetan Plateau
• Permafrost
• Glacier
• Stable isotope
• Water age
• Hydrology

Global warming has significantly impacted the hydrological processes in alpine cryosphere region. Water age is an essential descriptor of the hydrological function within a catchment. However, the mechanism of streamwater age variability remains unclear due to limited observational data and high altitudes of alpine catchment. In this study, long-term stable isotopic data on streamwater in a catchment in the central Tibetan Plateau (TP) were collected to assess the water age using the sine-wave approach and gamma distribution. Results showed that the mean streamwater age was 77 days, and that 30 % of streamwater was less than 41 days old on average. The streamwater age in this study was relatively younger than that in low-elevation natural catchments, indicating that the rapid drainage process occurs within the glacier and permafrost catchment. The fraction of young water (Fyw) of the streamwater decreased from 39 % at an upstream site to 28 % at the outlet, revealing the impact of permafrost (low Fyw: 25 %) on streamwater age. These variabilities were related to glacier and permafrost coverage, specifically in catchments with higher glacier coverage that are prone to have a lower water age. Temporally, the streamwater age was significantly influenced by precipitation, relative humidity, and glacier change and, to a lesser extent, permafrost change. Mechanically, glacier and permafrost changes influenced the water age by increasing the vertical flowpath length. This study provides new insights into the change in hy-drological processes in alpine headwater catchments under global warming.

• 单位
  中国科学院研究生院