Ning et al. (2026) Forty-year data analysis of droughts and drought-flood dynamics: impacts of cascading reservoirs

Identification

• Journal: Journal of Hydrology
• Year: 2026
• Date: 2026-01-17
• Authors: Yinan Ning, Joao Nádson Granja Nunes, Jichen Zhou, Jantiene Baartman, Franciane Mendonça dos Santos, Xuejun Liu, Lihua Ma, COEN J. RITSEMA, Wei Zhang
• DOI: 10.1016/j.jhydrol.2026.134957

Research Groups

• Soil Physics and Land Management Group, Wageningen University and Research, Wageningen, Netherlands
• Interdisciplinary Research Center for Agriculture Green Development in Yangtze River Basin, College of Resources and Environment, Southwest University, Chongqing, China
• State Key Laboratory of Nutrient Use and Management, College of Resources & Environmental Sciences, National Academy of Agriculture Green Development, China Agricultural University, Beijing, China
• IDL- Instituto Dom Luiz, Faculdade de Ciências da Universidade de Lisboa, Lisboa, Portugal

Short Summary

This study developed an inflow-driven cascading reservoir release framework within SWAT+ to assess the impacts of coordinated reservoir operations on drought propagation and drought-flood dynamics in the Yangtze River Basin from 1980-2020. It found that cascading reservoirs generally aggravated hydrological drought duration and frequency while decreasing intensity, and had mixed effects on drought-flood abrupt alternations across different river sections.

Objective

• To identify the propagation between meteorological drought and hydrological drought in the Yangtze River Basin (YRB) during 1980–2020.
• To analyze the specific variations in monthly meteorological and hydrological drought-flood abrupt alternation events during this period.
• To investigate how cascading reservoirs influence the occurrence and propagation of these events.

Study Configuration

• Spatial Scale: Yangtze River Basin (YRB), covering more than 1.8 million square kilometers, divided into 185 subbasins and 7223 Hydrologic Response Units (HRUs).
• Temporal Scale: 40-year period from 1980 to 2020. A 5-year warm-up period (1980–1984), calibration period (1985–2009), and validation period (2010–2019) were used for the model.

Methodology and Data

• Models used: Soil and Water Assessment Tool+ (SWAT+), enhanced with an inflow-driven cascading reservoir release framework that incorporates seasonally adaptive release rules.
• Data sources:
  • Digital Elevation Model (DEM): Hole-filled seamless SRTM data V4 (90 m spatial resolution, 2018).
  • Land Use and Land Cover (LUCC) (crop map): A developed crop map of the YRB (500 m spatial resolution, 2012).
  • Soil type: National Earth System Science Data Center (1000 m spatial resolution, 2018).
  • Meteorological data (precipitation, temperature, wind speed, evaporation, relative humidity, solar radiation): Resource and Environment Science and Data Center (196 stations, 1980–2020).
  • Reservoirs (catchment area, total storage): Global Reservoir and Dam (GRanD) Database (1980–2020).
  • River network: Resource and Environment Science and Data Center (2019).
  • Runoff (daily and monthly observed): Hydrology Yearbook of the People's Republic of China (7 stations, 1980–2020).
  • Drought indices: Standardized Precipitation Evapotranspiration Index (SPEI) for meteorological drought, Standardized Streamflow Index (SSI) for hydrological drought, and Long-cycle Drought-Flood Abrupt Alternation Index (LDFAI) for drought-flood dynamics.
  • Trend analysis: Non-parametric Mann-Kendall (M-K) test.
  • Environmental flow requirements (EFR): Variable Monthly Flow (VMF) method.

Main Results

• The lag between meteorological drought (MD) and hydrological drought (HD) events progressively increased from 22 days in the upstream section to 54 days in the downstream section of the YRB.
• Meteorological and hydrological droughts exhibited inconsistent spatio-temporal patterns; MDs were most prevalent in autumn (August to November), while HDs predominantly concentrated in summer (May to August).
• Cascading reservoirs increased the duration and frequency of HD events by approximately 20 % across the YRB, while decreasing their intensity by about 4 %.
• Cascading reservoirs alleviated 75 % of drought-to-flood (DTF) events in the downstream section but exacerbated 21 % of flood-to-drought (FTD) events in the upper and middle sections of the YRB.
• The long-cycle hydrological drought-flood abrupt alternation index (LDFAIh) showed a significant declining trend in the YRB, indicating an overall shift from flood to drought conditions.
• Cascading reservoirs did not alter environmental flow requirements (EFR) compliance in the upstream section. However, they resulted in an average 7-time transition from non-compliance to compliance with EFR in the midstream section (December to May) and 28 times in the downstream section (October to March), while also causing 10 times transition from compliance to non-compliance in the downstream section.

Contributions

• Developed and implemented an inflow-driven cascading reservoir release framework within the SWAT+ model, enabling dynamic simulation of coordinated reservoir operations with seasonally adaptive rules, which overcomes limitations of static or independently parameterized models.
• Provided a comprehensive basin-scale assessment of the cumulative impacts of cascading reservoirs on drought propagation and drought-flood abrupt alternations in a complex large river basin (Yangtze River Basin).
• Demonstrated the value of embedding operational realism and human-influenced operation logic into large-scale hydrological models to accurately capture the systemic influence of cascading reservoirs on hydroclimatic extremes.
• Offered a transferable and numerically tractable framework for simulating the effects of cascading reservoirs, supporting integrated and adaptive reservoir management strategies in other large basins under nonstationary hydroclimatic regimes.

Funding

• China Scholarship Council (No. 201913043)
• Hainan University
• The Key Laboratory of Low-carbon Green Agriculture (Ministry of Agriculture and Rural Affairs)
• The State Cultivation Base of Eco-agriculture for Southwest Mountainous Land (Southwest University)

Citation

@article{Ning2026Fortyyear,
  author = {Ning, Yinan and Nunes, Joao Nádson Granja and Zhou, Jichen and Baartman, Jantiene and Santos, Franciane Mendonça dos and Liu, Xuejun and Ma, Lihua and RITSEMA, COEN J. and Zhang, Wei},
  title = {Forty-year data analysis of droughts and drought-flood dynamics: impacts of cascading reservoirs},
  journal = {Journal of Hydrology},
  year = {2026},
  doi = {10.1016/j.jhydrol.2026.134957},
  url = {https://doi.org/10.1016/j.jhydrol.2026.134957}
}