Wu et al. (2026) Revegetation-induced drought propagation shifts prolong hydrological drought recovery on the Loess Plateau, China

Identification

• Journal: Agricultural Water Management
• Year: 2026
• Date: 2026-06-25
• Authors: Jiefeng Wu, Ya Peng, Wenxue Wang, Huaxia Yao, Guoqing Wang, Yi Cui, Jianzhu Li, Shifeng Xu, X J Li
• DOI: 10.1016/j.agwat.2026.110563

Research Groups

• College of Civil Engineering, Hefei University of Technology, Hefei, China
• School of Hydrology and Water Resources, Nanjing University of Information Science and Technology, Nanjing, China
• Inland Waters Unit, Environmental Monitoring and Reporting Branch, Ontario Ministry of Environment, Conservation and Parks, Dorset, Ontario, Canada
• Nanjing Hydraulic Research Institute, Nanjing, China
• State Key Laboratory of Hydraulic Engineering Intelligent Construction and Operation, Tianjin University, Tianjin, China
• Hydrology Bureau, Yellow River Conservancy Commission, Zhengzhou, China

Short Summary

This study investigates how large-scale revegetation on China's Loess Plateau, driven by the "Grain for Green Program" (GPP) since 1999, alters meteorological-hydrological drought propagation and hydrological drought recovery. It reveals that revegetation weakens the coupling between meteorological and hydrological droughts, prolongs hydrological drought recovery, and intensifies water shortage, with varying impacts depending on specific vegetation types.

Objective

• To disentangle the impacts and possible mechanisms of vegetation restoration on the meteorological-hydrological drought cascade and hydrological drought evolution (e.g., recovery duration and water shortage intensity during hydrological droughts) in water-constrained basins on the Loess Plateau.
• To reveal the response patterns of meteorological-to-hydrological drought propagation before and after large-scale vegetation restoration.
• To explore how hydrological drought characteristics (e.g., duration, severity, recovery time) and associated water shortage intensity respond to vegetation restoration and varied vegetation types.
• Hypotheses: (i) Large-scale revegetation under the GPP weakens the coupling between meteorological drought and hydrological drought, and prolongs the recovery period of hydrological drought; (ii) Different vegetation types impose disparate influences on drought propagation efficiency, hydrological drought features, and water deficit intensity.

Study Configuration

• Spatial Scale: Three representative watersheds (Dali, Xinshui, and Yan rivers) in the central-southern Loess Plateau, China, with areas of 3900 km², 3974 km², and 5891 km² respectively.
• Temporal Scale: 1961–2021, divided into pre-GPP (1961–1998) and post-GPP (2000–2021) periods.

Methodology and Data

• Models used:
  • Standardized Precipitation Evapotranspiration Index (SPEI) for meteorological drought assessment.
  • Streamflow Standardized Index (SSI) for hydrological drought assessment.
  • Run theory for identifying drought characteristics (duration, severity, intensity, recovery time).
  • Pearson correlation coefficient (PCC) for analyzing response relationships and time lags between SPEI and SSI.
  • Sankey diagram for visualizing meteorological-hydrological drought propagation patterns.
  • Cumulative difference curve – rank test for detecting inconsistencies in hydro-meteorological time series.
• Data sources:
  • Monthly flow data (1961–2021) from downstream hydrological stations (Suide, Daning, Ganguyi) sourced from the Yellow River Hydrological Yearbook.
  • Monthly observed precipitation data from meteorological stations (Suide, Daning, Ganguyi) from the China Meteorological Administration.
  • ERA5-Land reanalysis precipitation data (primary meteorological input).
  • Daily potential evapotranspiration (PET) data from China Meteorological Forcing Dataset version 2.0 (CMFD 2.0), calculated using the FAO−56 Penman-Monteith equation.
  • 30 m China Land Cover Dataset (CLCD) (Yang and Huang, 2022) based on Landsat satellite imagery, reclassified into six consolidated categories (cropland, forestland, grassland, water, construction, unused land).

Main Results

• After 1999, the correlation between the hydrological drought index (SSI−1) and the meteorological drought index (SPEI) significantly weakened, with maximum divergence observed at the 9-month time scale across all three basins.
• The propagation of meteorological drought (MD) to hydrological drought (HD) shifted from a temporally concentrated and simple cascading process before 1999 to a spatiotemporally dispersed, multi-path, and cross-level cascading process after 1999. For instance, the proportion of HD at or above mild drought (L1) when MD was at no-drought level increased to 32.19% post-1999.
• Hydrological droughts consistently exacerbated across all basins after 1999, characterized by:
  • Increased mean drought duration (e.g., Xinshui river: from 7.64 months to 11.67 months).
  • Increased mean drought severity (e.g., Dali river: from 4.40 to 5.82).
  • Prolonged mean recovery time (e.g., Xinshui river: from 3.36 months to 4.33 months).
  • Increased absolute value of mean average shortage flow (ASF) (e.g., Yan river: from −2.81 m³/s to −4.00 m³/s).
• Annual streamflow in all three basins showed a significant decreasing trend (0.04 to 0.08 m³/s per year, p < 0.01), while potential evapotranspiration (PET) exhibited a significant increasing trend (0.33 to 1.18 mm per year, p < 0.01) in Dali and Xinshui basins.
• Grassland area showed a positive correlation with hydrological drought frequency in the Dali and Yan river basins (significant in Yan river), suggesting it may intensify water resource consumption and drought frequency.
• Forestland exhibited weak correlations with all drought characteristics, likely due to a balance between its water conservation capacity and evapotranspiration.
• Cropland's impacts on drought characteristics displayed significant regional variations, possibly linked to differences in agricultural practices.

Contributions

• Clarifies the regulatory mechanism of vegetation restoration on drought propagation, highlighting ecological benefits alongside increased hydrological drought risks.
• Enriches the understanding of how different vegetation types influence drought propagation and hydrological drought evolution, moving beyond aggregated vegetation metrics.
• Provides novel insights into vegetation-drought interactions in semi-arid, ecologically restored landscapes.
• Offers scientific support for integrated eco-restoration and water resource management strategies in regions like the Loess Plateau, aiming for a coordinated trade-off between ecological benefits and hydrological risks.

Funding

• National Key Research and Development Program of China (Grant No. 2024YFC3211302)
• National Natural Science Foundation of China (Grant No. 52379013)
• Anhui Provincial Natural Science Foundation (2308085US13)
• Natural Science Foundation of Fujian Province, China (Grant No. 2024J01993)
• State Key Laboratory of Hydraulic Engineering Intelligent Construction and Operation, Tianjin University (HESS−2412)

Citation

@article{Wu2026Revegetationinduced,
  author = {Wu, Jiefeng and Peng, Ya and Wang, Wenxue and Yao, Huaxia and Wang, Guoqing and Zhou, Yuliang and Cui, Yi and Li, Jianzhu and Xu, Shifeng and Li, X J},
  title = {Revegetation-induced drought propagation shifts prolong hydrological drought recovery on the Loess Plateau, China},
  journal = {Agricultural Water Management},
  year = {2026},
  doi = {10.1016/j.agwat.2026.110563},
  url = {https://doi.org/10.1016/j.agwat.2026.110563}
}