Fang et al. (2026) Hydrological impact of near-surface soil warming in China’s Three Rivers Source Region during the seasonally heterogeneous precipitation period from 1998-2017

Identification

• Journal: Theoretical and Applied Climatology
• Year: 2026
• Date: 2026-01-10
• Authors: Xuewei Fang, Xing Chen, Chen Cheng, Yige Xu, Shihua Lyu
• DOI: 10.1007/s00704-025-05989-9

Research Groups

• Climate Change and Resource Utilization in Complex Terrain Regions Key Laboratory of Sichuan Province, Chengdu Plain Urban Meteorology and Environment Observation and Research Station of Sichuan Province, Sichuan Provincial Engineering Research Center for Meteorological Disaster Prediction and Early Warning, School of Atmospheric Sciences, Chengdu University of Information Technology, Chengdu, China
• Heavy Rain and Drought-Flood Disasters in Plateau and Basin Key Laboratory of Sichuan Province, Institute of Tibetan Plateau Meteorology, China Meteorological Administration, Chengdu, China
• Southwest Institute of Technical Physics, Chengdu, China
• Max Planck Institute for Meteorology, Hamburg, Germany

Short Summary

This study quantifies the differential hydrological impacts of permafrost versus seasonally frozen ground (SFG) degradation in China's Three Rivers Source Region (TRSR) from 1998-2017, revealing that permafrost degradation, particularly in areas with low thermal stability, is becoming the dominant control on long-term hydrological cycles.

Objective

• To quantify the contrasting thermal regimes of frozen soils and their basin-scale hydrological impacts across the Three Rivers Source Region (TRSR) during the pronounced wetting period from 1998 to 2017, specifically comparing the differential hydrological consequences of permafrost versus seasonally frozen ground (SFG) degradation.

Study Configuration

• Spatial Scale: Three Rivers Source Region (TRSR) on the Tibetan Plateau, China, encompassing the Yellow River Source Region (YeSR), Yangtze River Source Region (YaSR), and Lancang River Source Region (LcSR). The region spans 73.45–104.70°E and 26.85–39.96°N, with a mean elevation of 4587 meters.
• Temporal Scale: 1998–2017 (20 years), focusing on seasonally heterogeneous precipitation periods.

Methodology and Data

• Models used: No specific hydrological models (e.g., ISBA, mHM) were used for simulation. The study primarily relies on observational data analysis, statistical correlations, and moving averages.
• Data sources:
  • Observed soil temperatures at 5, 10, 20, and 40 cm depths from 21 meteorological stations (1998–2017).
  • Daily rainfall and snow depth records from the 21 meteorological stations (Qinghai Meteorological Bureau, China).
  • China Natural Runoff Dataset (CNRD) v1.0, a 0.25° × 0.25° gauge-based gridded product (1961–2018, National Tibetan Plateau Data Center).
  • Tibetan Plateau permafrost map (Zou et al., 2017) for classifying permafrost and seasonally frozen ground (SFG) areas.
  • Ground Freezing Index (GFI) derived from 5 cm soil temperatures.
  • Recession coefficient (RC) calculated from mean daily discharge in November and February.

Main Results

• The observed precipitation pattern, characterized by increased warm season rainfall and decreased cold season snow depth, accelerates near-surface soil warming in SFG catchments and amplifies subsurface thermal sensitivity in permafrost-dominated basins.
• Thermal degradation in permafrost-dominated catchments exerts a more immediate influence on streamflow than in SFG basins.
• Hydrological responses in permafrost catchments are contingent upon thermal stability: basins with low thermal stability (rapid Ground Freezing Index (GFI) decline) exhibit strong runoff sensitivity to permafrost dynamics, whereas basins with high thermal stability (moderate GFI decline) display significant streamflow effects only over longer timescales (e.g., 7-year moving average).
• Warm season rainfall significantly increased in the YeSR (27.88 mm per decade) and YaSR (36.37 mm per decade), but declined in the LcSR (−25.18 mm per decade). Cold season snow depth increased in the YeSR (0.40 cm per decade) but decreased in the YaSR (−0.34 cm per decade) and LcSR (−0.64 cm per decade).
• In the SFG-dominated YeSR, soil temperatures rose consistently throughout the profile, with the largest warming at 40 cm (0.93 °C per decade, p < 0.05). The shallow gradient (ΔT 40-20) increased significantly by 0.24 °C per decade (p < 0.05).
• In the permafrost-dominated YaSR, significant warming occurred only at 20 cm (0.20 °C per decade, p < 0.05) and 40 cm (0.91 °C per decade, p < 0.05), while near-surface soils cooled significantly.
• Regionally, permafrost basins exhibited a significant runoff increase from 1998–2017, with larger monthly increments in the cold season, leading to attenuated seasonal runoff amplitude. SFG basins showed rising trends in the cold season and declining trends in the warm season.
• The GFI decline and recession coefficient (RC) are significantly negatively correlated in permafrost regions, especially at longer timescales (3- to 7-year moving averages), indicating that permafrost thermal impacts on base flow become detectable over longer periods.
• Thermal degradation in the LcSR (GFI decline: 105.48 °C·d per decade, p < 0.10) proceeds roughly twice as rapidly as in the YaSR (56.17 °C·d per decade), coinciding with a markedly stronger runoff sensitivity to permafrost change.
• The YeSR exhibits a more rapid streamflow response to permafrost retreat (GFI decline: 162.80 °C·d per decade, p < 0.05) than to SFG warming (55.95 °C·d per decade, p < 0.05).

Contributions

• Provides a novel perspective on hydrological sensitivity to frozen ground degradation by explicitly resolving and comparing permafrost and seasonally frozen ground (SFG) regimes across the Three Rivers Source Region (TRSR).
• Quantifies the contrasting thermal dynamics and basin-scale hydrological impacts of permafrost versus SFG degradation during a period of pronounced wetting.
• Demonstrates that the streamflow response to permafrost degradation is contingent upon permafrost thermal stability, which is itself strongly modulated by precipitation changes.
• Highlights that permafrost degradation is becoming the dominant control on long-term hydrological cycles across the TRSR, emphasizing the need for further quantification of these hydrological feedbacks for the "Asian Water Tower."

Funding

• National Natural Science Foundation of China (42475091, 42275080)
• Natural Science Foundation of Sichuan Province (2025ZNSFSC1133)
• Youth Innovation Team of China Meteorological Administration “Climate change and its impacts in the Tibetan Plateau” (NO. CMA2023QN16)

Citation

@article{Fang2026Hydrological,
  author = {Fang, Xuewei and Chen, Xing and Jiang, Xingwen and Cheng, Chen and Xu, Yige and Fraedrich, Klaus and Lyu, Shihua},
  title = {Hydrological impact of near-surface soil warming in China’s Three Rivers Source Region during the seasonally heterogeneous precipitation period from 1998-2017},
  journal = {Theoretical and Applied Climatology},
  year = {2026},
  doi = {10.1007/s00704-025-05989-9},
  url = {https://doi.org/10.1007/s00704-025-05989-9}
}