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<p>The Yalong and Dadu River basins (Yangtze headwaters) serve as critical “water towers” for ecosystems and strategic diversions. However, climate warming may decouple atmospheric inputs from hydrological responses, exposing the limitations of traditional runoff-centric assessments that overlook terrestrial water storage dynamics. To address this gap, this study develops a probability-based diagnostic framework integrating the SWAT model with a novel Water Balance Resilience Index (WBRI) to evaluate basin health evolution (1961–2018). Annual water storage change was quantified via the hydrological water balance, standardized into a Normalized Storage Index (NSI), and transformed into the WBRI by fitting probability distributions to absolute anomaly magnitudes and mapping them to hydrological return periods on a continuous 0–1 health scale. Results reveal a significant non-linear divergence: while precipitation and evapotranspiration in the Dadu basin declined markedly, runoff remained relatively stable. This stability may be associated with cryospheric and storage-related buffering, which partly compensates for precipitation deficits through enhanced cryospheric contributions and reduced evapotranspiration under water-limited conditions. Phase-space diagnosis identified a recurring flux–state decoupling pattern, with the “High Flux–Low State” anomaly occurring at comparable frequencies in the Source Region and Sink group (both 19.8%) and varying across subbasins from 13.8% to 22.4%. This suggests that stable discharge may exert a “masking effect,” concealing potential depletion of terrestrial water storage and legacy cryospheric reserves. Furthermore, the WBRI indicates that since 2010, both basins have tended toward a more vulnerable or tighter water-balance state, with reduced resilience to hydro-climatic variability. These findings support a flux–state collaborative monitoring framework. For the West Route Diversion Project, a hierarchical “Mainstem Control + Tributary Quotas” mode is suggested, in which transferable water limits consider storage-state indicators rather than runoff abundance alone. This may help reduce long-term storage-depletion risk and support alpine ecosystem sustainability.</p>

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Flux-state decoupling reveals water-balance resilience in Tibetan headwaters

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月6日

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  • Junfei Yang,
  • Bing Yan,
  • En Li,
  • Xuenan Yang,
  • Changshuo Huang

摘要

The Yalong and Dadu River basins (Yangtze headwaters) serve as critical “water towers” for ecosystems and strategic diversions. However, climate warming may decouple atmospheric inputs from hydrological responses, exposing the limitations of traditional runoff-centric assessments that overlook terrestrial water storage dynamics. To address this gap, this study develops a probability-based diagnostic framework integrating the SWAT model with a novel Water Balance Resilience Index (WBRI) to evaluate basin health evolution (1961–2018). Annual water storage change was quantified via the hydrological water balance, standardized into a Normalized Storage Index (NSI), and transformed into the WBRI by fitting probability distributions to absolute anomaly magnitudes and mapping them to hydrological return periods on a continuous 0–1 health scale. Results reveal a significant non-linear divergence: while precipitation and evapotranspiration in the Dadu basin declined markedly, runoff remained relatively stable. This stability may be associated with cryospheric and storage-related buffering, which partly compensates for precipitation deficits through enhanced cryospheric contributions and reduced evapotranspiration under water-limited conditions. Phase-space diagnosis identified a recurring flux–state decoupling pattern, with the “High Flux–Low State” anomaly occurring at comparable frequencies in the Source Region and Sink group (both 19.8%) and varying across subbasins from 13.8% to 22.4%. This suggests that stable discharge may exert a “masking effect,” concealing potential depletion of terrestrial water storage and legacy cryospheric reserves. Furthermore, the WBRI indicates that since 2010, both basins have tended toward a more vulnerable or tighter water-balance state, with reduced resilience to hydro-climatic variability. These findings support a flux–state collaborative monitoring framework. For the West Route Diversion Project, a hierarchical “Mainstem Control + Tributary Quotas” mode is suggested, in which transferable water limits consider storage-state indicators rather than runoff abundance alone. This may help reduce long-term storage-depletion risk and support alpine ecosystem sustainability.