Wang et al. (2026) Evolution characteristics and driving mechanisms of ecological drought from a terrestrial ecosystem perspective

Identification

• Journal: Journal of Hydrology Regional Studies
• Year: 2026
• Date: 2026-02-25
• Authors: Fei Wang, Ruyi Men, Yi Zhang, Shaofeng Yan, Shikai Gao, Hexin Lai, Mengting Du, Wenhan Yu, Kai Feng, Yanbin Li, Shengzhi Huang, Qingqing Tian, Jihong Qu, Kun Ren, Haibo Yang
• DOI: 10.1016/j.ejrh.2026.103287

Research Groups

• School of Water Conservancy, North China University of Water Resources and Electric Power, Zhengzhou 450046, China
• CSG Peak and Frequency Regulation Power Generation Co., Ltd. Operation Branch, Guangzhou 511400, China
• Hubei Institute of Water Resources Survey and Design Co., LTD, Wuhan 430070, China
• School of Water Conservancy and Transportation, Zhengzhou University, Zhengzhou 450001, China

Short Summary

This study systematically investigated the spatiotemporal evolution patterns and driving mechanisms of ecological drought in the Yellow River Basin (YRB) from 1982 to 2022 using a novel Standardized Ecological Water Deficit Index (SEWDI). It found a significant basin-wide drying trend with westward migration of drought centers, primarily driven by evapotranspiration (ET) and the Atlantic Multidecadal Oscillation (AMO).

Objective

• To reveal the multi-timescale evolution characteristics of ecological drought in the YRB.
• To clarify the spatial distribution patterns of ecological drought in the YRB.
• To analyze typical drought events and return periods of ecological drought.
• To characterize the dynamic evolution trends of ecological drought at the grid level.
• To investigate the driving roles of climate factors and atmospheric circulation factors on ecological drought.

Study Configuration

• Spatial Scale: Yellow River Basin (YRB), China, covering an area of approximately 795,000 square kilometers, divided into eight sub-regions.
• Temporal Scale: 1982 to 2022 (41 years), analyzed at monthly, seasonal, decadal, and multi-time scales (1–24 months).

Methodology and Data

• Models used:
  • Standardized Ecological Water Deficit Index (SEWDI) (developed in study)
  • Surface Energy Balance System (SEBS) model and PySEBS toolkit
  • FAO-56 crop coefficient method
  • Improved run theory (three-tiered threshold system: X0=0, X1=–0.3, X2=–0.5)
  • Copula joint probability models (Gaussian, t, Clayton, Frank, Gumbel)
  • Modified Mann-Kendall (MMK) method
  • Cross Wavelet Transform (Partial Wavelet Coherence (PWC), Multiple Wavelet Coherence (MWC))
  • XGBoost-SHAP machine learning framework
• Data sources:
  • Reanalysis/Assimilation: Famine Early Warning Systems Network Land Data Assimilation System (FLDAS) dataset (Air humidity (AH), Evapotranspiration (ET), Precipitation (PC), Soil moisture (SM)) at approximately 0.1° spatial resolution.
  • Remote Sensing: Normalized Difference Vegetation Index (NDVI) (National Earth System Science Data Center) at 8 km spatial resolution; Potential evapotranspiration (ET0) (National Tibetan Plateau Data Center) at 1 km spatial resolution; Actual evapotranspiration (ETa) (Harvard University, USGS) at 8 km spatial resolution.
  • Indices: Ten atmospheric circulation indices (El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO), Arctic Oscillation (AO), Atlantic Multidecadal Oscillation (AMO), Dipole Mode Index (DMI), North Pacific Index (NPI), Pacific North America Index (PNA), Southern Oscillation Index (SOI), Sunspot Index (SSI)).

Main Results

• Overall Trend: The Standardized Ecological Water Deficit Index (SEWDI) in the YRB showed a significant downward trend (–0.017 per decade) from 1982 to 2022, indicating increasing ecological drought. The AL region exhibited the steepest decline (–0.043 per decade).
• Spatial Evolution: Ecological drought centers showed a distinct westward migration from the 1980s to the 2010s. In the 2010s, over 91% of western areas (AL region) were affected by drought.
• Temporal Characteristics: Drought intensification was particularly pronounced in December (Zs = –1.33) and winter (Zs = –1.46), with 97.79% and 94.25% of the basin showing aggravating trends, respectively. Longer cumulative time scales correlated with lower fluctuation frequency and prolonged dry-wet periods.
• Extreme Events: The most severe ecological drought event occurred from July 2019 to April 2020, lasting 10 months with a severity of 9.14. It peaked in February 2020, affecting 98.08% of the basin, with extreme drought levels in the LS and HL regions. The return period for this event exceeded 10 years for the basin, and over 100 years for the AL and LL regions.
• Climatic Driving Factors: Evapotranspiration (ET) was identified as the dominant climatic driver (Percentage of Significant Power (POSP) = 11.78%). The synergistic combination of ET, Air Humidity (AH), and Soil Moisture (SM) exhibited the strongest explanatory power (POSP = 25.42%).
• Atmospheric Circulation Driving Factors: The Atlantic Multidecadal Oscillation (AMO) was the primary circulation factor influencing ecological drought in the YRB (contribution of 0.158), with high AMO values exacerbating drought. The Sunspot Index (SSI) and Pacific Decadal Oscillation (PDO) showed mitigating effects.

Contributions

• Developed a novel Standardized Ecological Water Deficit Index (SEWDI) that integrates vegetation dynamics and hydrological processes, providing a more comprehensive and ecosystem-specific assessment of water stress compared to traditional drought indices.
• Provided refined quantitative insights into the spatiotemporal differentiation patterns and driving mechanisms of ecological drought in the Yellow River Basin through a multidimensional and multi-method integrated analytical approach.
• Utilized advanced methodologies, including improved run theory, Copula functions, Modified Mann-Kendall (MMK), and the XGBoost-SHAP explainable machine learning framework, for robust trend detection, uncertainty modeling, and interpretable driver contribution analysis.
• Identified specific ecological drought "hot spots" (AL and LL regions with year-round intensification) and critical periods (December and winter) within the basin, offering a scientific basis for targeted and localized drought prevention and control strategies.
• Quantified the dominant roles of evapotranspiration (ET) as a climatic driver and the Atlantic Multidecadal Oscillation (AMO) as a primary atmospheric circulation factor, linking basin-scale drought variations to interdecadal ocean-atmosphere interactions.

Funding

• National Key R&D Program of China (grant number 2023YFC3006603)
• National Natural Science Foundation of China (grant number 42401022 and 42301024)
• Innovation Fund for doctoral of North China University of Water Resources and Electric Power (grant number BCJJ202404)
• Hubei Province Water Conservancy Research Project (HBSLKY202310)
• The Open Research Fund of Key Laboratory of River Basin Digital Twinning of Ministry of Water Resources (grant number Z0202042022)
• Key Research Projects of Higher Education Institutions in Henan Province (grant number 24A570005)
• Scientific and Technological Research Projects in Henan Province (grant number 242102321005)
• Key Research and Development Special Project of Henan Province (grant number 251111210700)

Citation

@article{Wang2026Evolution,
  author = {Wang, Fei and Men, Ruyi and Zhang, Yi and Yan, Shaofeng and Gao, Shikai and Lai, Hexin and Du, Mengting and Yu, Wenhan and Feng, Kai and Li, Yanbin and Huang, Shengzhi and Tian, Qingqing and Qu, Jihong and Ren, Kun and Yang, Haibo},
  title = {Evolution characteristics and driving mechanisms of ecological drought from a terrestrial ecosystem perspective},
  journal = {Journal of Hydrology Regional Studies},
  year = {2026},
  doi = {10.1016/j.ejrh.2026.103287},
  url = {https://doi.org/10.1016/j.ejrh.2026.103287}
}