16 Mar 2022
16 Mar 2022
Status: this preprint is currently under review for the journal HESS.

Frozen-soil hydrological modeling for a mountainous catchment at northeast of the Tibetan Plateau

Hongkai Gao1,2, Chuntan Han3, Rensheng Chen3, Zijing Feng2, Kang Wang1,2, Fabrizio Fenicia4, and Hubert Savenije5 Hongkai Gao et al.
  • 1Key Laboratory of Geographic Information Science (Ministry of Education of China), East China Normal University, Shanghai, China
  • 2School of Geographical Sciences, East China Normal University, Shanghai, China
  • 3Qilian Alpine Ecology and Hydrology Research Station, Key Lab. of Ecohydrology of Inland River Basin, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
  • 4Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dubendorf, Switzerland
  • 5Delft University of Technology, Delft, the Netherlands

Abstract. Increased attention directed at frozen-soil hydrology has been prompted by climate change. In spite of an increasing number of field measurements and modeling studies, the impact of frozen-soil on hydrological processes at the catchment scale is still unclear. However, frozen-soil hydrology models have mostly been developed based on a “bottom-up” approach, i.e. by aggregating prior knowledge at pixel scale, which is an approach notoriously suffering from equifinality and data scarcity. Therefore, in this study, we explore the impact of frozen-soil at catchment-scale, following a “top-down” approach, implying: expert-driven data analysis qualitative perceptual model quantitative conceptual model testing of model realism. The complex mountainous Hulu catchment, northeast of the Tibetan Plateau, was selected as the study site. Firstly, we diagnosed the impact of frozen-soil on catchment hydrology, based on multi-source field observations, model discrepancy, and our expert knowledge. Two new typical hydrograph properties were identified: the low runoff in the early thawing season (LRET) and the discontinuous baseflow recession (DBR). Secondly, we developed a perceptual frozen-soil hydrological model, to explain the LRET and DBR properties. Thirdly, based on the perceptual model and a landscape-based modeling framework (FLEX-Topo), a semi-distributed conceptual frozen-soil hydrological model (FLEX-Topo-FS) was developed. The results demonstrate that the FLEX-Topo-FS model can represent the effect of soil freeze/thaw processes on hydrologic connectivity and groundwater discharge and significantly improve hydrograph simulation, including the LRET and DBR events. Furthermore, its realism was confirmed by alternative multi-source and multi-scale observations, particularly the freezing and thawing front in the soil, the lower limit of permafrost, and the trends in groundwater level variation. To the best of our knowledge, this study is the first report of LRET and DBR processes in a mountainous frozen-soil catchment. The FLEX-Topo-FS model is a novel conceptual frozen-soil hydrological model, which represents these complex processes and has potential for wider use in the vast Tibetan Plateau and other cold mountainous regions.

Hongkai Gao et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2022-98', Anonymous Referee #1, 10 Apr 2022
  • RC2: 'Comment on hess-2022-98', Anonymous Referee #2, 24 May 2022

Hongkai Gao et al.

Hongkai Gao et al.


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Short summary
Frozen-soil hydrology is one of the 23 major unsolved problems in hydrology. In this study, we developed a novel conceptual frozen-soil hydrological model, FLEX-Topo-FS. The model successfully reproduced the soil freeze/thaw process, and its impacts on hydrologic connectivity, runoff generation and groundwater. We believe this study is a breakthrough, giving us new insights on frozen-soil hydrology, with board implications to predict cold region hydrology in future.