Insights into the streamwater age in the headwater catchments covered by glaciers and permafrost, Central Tibetan Plateau

Shaoyong Wang; Xiaobo He; Shichang Kang; Fangpin Yan; Hui Fu; Xiaofeng Hong; Yuang Xue; Zijing Feng

doi:10.1016/j.scitotenv.2022.161337

Insights into the streamwater age in the headwater catchments covered by glaciers and permafrost, Central Tibetan Plateau

Sci Total Environ. 2023 Mar 25:866:161337. doi: 10.1016/j.scitotenv.2022.161337. Epub 2023 Jan 2.

Authors

Shaoyong Wang¹, Xiaobo He², Shichang Kang¹, Fangpin Yan³, Hui Fu⁴, Xiaofeng Hong⁵, Yuang Xue¹, Zijing Feng⁶

Affiliations

¹ State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China.
² State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China. Electronic address: hxb@lzb.ac.cn.
³ State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.
⁴ State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources and Hydropower Research, Beijing 100038, China.
⁵ Water Resources Department, Changjiang River Scientific Research Institute, Wuhan 430010, China.
⁶ School of Geographical Sciences, East China Normal University, Shanghai 200000, China.

PMID: 36603633
DOI: 10.1016/j.scitotenv.2022.161337

Abstract

Improving our understanding of streamwater age knowledge is critical for revealing the complex hydrological processes in alpine cryosphere catchments. However, few studies on water age have been conducted in alpine cryosphere catchments due to the complicated and inclement environment. In this study, the Buqu catchment, a typical alpine catchment covered by glaciers and permafrost on the central Tibetan Plateau (TP), was selected as the study area. Using the sine-wave approach and a gamma model based on the seasonal cycle of stable isotopes in water, the young water fraction (F_yw) and mean transit time (MTT) of the Buqu catchment outlet and 23 sub-catchments was estimated to comprehensively reveal the potential driving mechanism of water age variability. The streamwater MTT for the entire catchment was 107 days, and 15.1 % of the streamwater was younger than 41 days on average. The estimated water age showed significant spatial heterogeneity with shorter water ages in high-elevation and glacier catchments and longer water ages in low-elevation and non-glacier catchments. Precipitation was the primary driver for spatial variations in water age, while the thickness of the permafrost active layer may function as an intermediate hub to drive water age variability. Mechanically, the thickness of the permafrost active layer controls the water ages by modifying the flow direction and length of water flow path. Spatially, this control mechanism is indirectly driven by the elevation gradient. The TDS concentration in streamwater is significantly related to water age, thus revealing a close link between water quality and hydrology. Our findings suggest that cryosphere retreats likely alter water age, thereby slowing water circulation rates and affecting water quality security under global warming. This study provides insights into the evolution of water ages, thereby deepening our understanding of the hydrological processes and guiding the protection of water resources in alpine headwater catchments.

Keywords: Alpine catchment; Hydrology; Mean transit time; Stable isotope; Water quality; Young water fraction.