Qiu et al. (2025) Spatiotemporal pattern of terrestrial ecological drought based on ecological water deficit in the Yellow River Basin

Identification

• Journal: Hydrology research
• Year: 2025
• Date: 2025-10-17
• Authors: Mengting Qiu, S. S. Jiang, Jianying Guo, Yongwei Zhu, Yating Liu, Liliang Ren
• DOI: 10.2166/nh.2025.054

Research Groups

• College of Hydrology and Water Resources, Hohai University, Nanjing, China
• Yinshanbeilu Grassland Eco-hydrology National Observation and Research Station, China Institute of Water Resources and Hydropower Research, Beijing, China
• The National Key Laboratory of Water Disaster Prevention, Hohai University, Nanjing, China
• Hubei Institute of Water Resources Survey and Design Co., Ltd, Hubei, China

Short Summary

This study developed a novel ‘Vegetation-Evapotranspiration-Water Balance’ framework to comprehensively assess the spatiotemporal patterns of terrestrial ecological drought (ED) in the Yellow River Basin (YRB) from 1982 to 2020, revealing a predominantly alleviating drought trend despite increasing ecological water requirements and consumption.

Objective

• To develop a ‘Vegetation-Evapotranspiration-Water Balance’ framework that integrates vegetation conditions, evapotranspiration, and water deficit for a comprehensive assessment of terrestrial ecological drought.
• To quantify the spatiotemporal patterns and evolutionary trends of terrestrial ecological drought in the Yellow River Basin from 1982 to 2020.
• To analyze the spatial distribution and evolutionary trends of Normalized Difference Vegetation Index (NDVI) and crop coefficients (kc) in the YRB.
• To investigate the driving mechanisms influencing NDVI variations and ecological drought indicators.

Study Configuration

• Spatial Scale: Yellow River Basin (YRB), spanning 795,000 km², divided into eight subregions based on secondary water resource zoning.
• Temporal Scale: 1982–2020 (39 years), with a change-point analysis identifying two sub-periods: 1982–2002 and 2003–2020. Monthly data were used.

Methodology and Data

• Models used:
  • Pettitt test (for identifying mutation points in time series)
  • Sen-MK method (Theil–Sen slope estimation and Mann–Kendall trend analysis for temporal trends)
  • Penman–Monteith formula (FAO-56) for calculating reference crop evapotranspiration (ET₀)
  • ‘Vegetation-Evapotranspiration-Water Balance’ framework (integrating NDVI, crop coefficients, Ecological Water Requirement (EWR), Ecological Water Consumption (EWC), and Ecological Water Deficit (EWD))
  • Pearson correlation analysis (for optimizing Vegetation Health Index (VHI) weighting parameters)
• Data sources:
  • Satellite: Normalized Difference Vegetation Index (NDVI) (0.05° resolution, NOAA), Vegetation Health Index (VHI) (4 km resolution, Figshare).
  • Reanalysis: Meteorological data (Surface Solar Radiation, Temperature, Relative Humidity, Wind speed at 10 m, Surface Thermal Radiation Downward, Precipitation) from ERA5-Land (0.1° resolution, Copernicus Climate Change Service).
  • Observation/Derived: Land Use/Cover Datasets (LUCC) (0.1° resolution, China's Land-Use/Cover Datasets - CNLUCC).

Main Results

• The Normalized Difference Vegetation Index (NDVI) in the YRB ranged from 0.05 to 0.8, showing an abrupt increase around 2003, with 95.3% of the basin area exhibiting increasing trends.
• Crop coefficients (kc) ranged from 0.1 to 0.8, peaking during the mid-growth stage (0.12–0.79). They displayed increasing trends predominantly in northern subregions (especially Subregions 3–5, covering >63.8% of their area) and decreasing patterns in southern regions.
• Ecological Water Requirement (EWR) ranged from 151–890 mm, exhibiting a pronounced southward-declining gradient, with peak values concentrated in Subregions 3–5.
• Ecological Water Consumption (EWC) ranged from 17–460 mm, demonstrating an opposite increasing trend from north to south, with maxima in Subregions 6–8.
• Ecological Water Deficit (EWD) ranged from 0–804 mm, mirroring the spatial distribution of EWR, with severe deficits concentrated in Subregions 3–5, coinciding with the "Ordos-Yulin Critical Water Deficit Zone."
• Despite overall increasing trends in EWR (69.3% of the basin area) and EWC (98.5% of the basin area), EWD showed a downward trend in 54.6% of the YRB, indicating a predominantly alleviating drought trend.
• Terrestrial ED was slightly alleviated in the upper reaches (Loop Irrigation Area, Subregion 1), remained stable in the middle reaches (Loess Plateau core, Subregions 2–4), and was significantly alleviated across the downstream alluvial plain (Subregions 6–8).
• Cross-validation with VHI showed high consistency in the mid-lower reaches but discrepancies in Subregions 2–4, attributed to acute water scarcity, delayed vegetation response, and subsurface heterogeneity.

Contributions

• Developed a novel ‘Vegetation-Evapotranspiration-Water Balance’ framework that provides a comprehensive and quantitative assessment of ecological drought by integrating vegetation conditions, evapotranspiration dynamics, and water supply-demand balance, moving beyond descriptive remote sensing indices.
• Provided a long-term (1982–2020) and basin-wide analysis of ecological drought evolution in the Yellow River Basin, addressing a critical gap in trend analysis at this scale.
• Elucidated the physio-ecological mechanisms of ecological drought by analyzing the complete process of ‘vegetation growth status – vegetation evapotranspiration – water supply and demand balance’, reflecting combined effects of meteorological conditions, soil moisture, and vegetation physiological status.
• Identified a significant change-point in NDVI around 2003, linking it to synergistic effects of ecological restoration policies and favorable climatic shifts, providing insights into regional vegetation dynamics.

Funding

• Yinshanbeilu Grassland Eco-hydrology National Observation and Research Station, China Institute of Water Resources and Hydropower Research (YSS202301)
• National Natural Science Foundation of China (52479009)

Citation

@article{Qiu2025Spatiotemporal,
  author = {Qiu, Mengting and Jiang, S. S. and Guo, Jianying and Zhu, Yongwei and Liu, Yating and Ren, Liliang},
  title = {Spatiotemporal pattern of terrestrial ecological drought based on ecological water deficit in the Yellow River Basin},
  journal = {Hydrology research},
  year = {2025},
  doi = {10.2166/nh.2025.054},
  url = {https://doi.org/10.2166/nh.2025.054}
}