Li et al. (2026) Optimization scheduling of cascade reservoirs under an ecological approach: a case study

Identification

• Journal: Scientific Reports
• Year: 2026
• Date: 2026-09-23
• Authors: Ji-Dong Li, Shuo Zhang, Gui-You Xiao, Fu Xi, Ming Lei, Wei-Bin Huang, Chu-Sheng Liang, Yang zhan
• DOI: 10.1038/s41598-026-70595-2

Research Groups

• College of Water Conservancy and Hydropower Engineering, Sichuan Agricultural University, Ya’an, Sichuan, China
• Tibet Development Investment Group Co., Ltd., Lhasa, China
• State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, China
• POWERCHINA Chengdu Engineering Corporation Limited, Chengdu, China
• Sichuan Port and Shipping Investment Group Co., Ltd., Chengdu, China

Short Summary

This study develops an ecological optimal dispatching framework for cascade reservoirs in the lower Yalong River Basin, incorporating minimum ecological flow requirements to balance hydropower generation and river ecosystem health. The proposed ecological scheme significantly reduces ecological alteration degrees by 19.84% to 58.6% across different hydrological years compared to conventional operations, while maintaining or increasing power output in normal and dry years.

Objective

• To develop an optimal dispatching model for cascade hydropower stations in the lower Yalong River that incorporates ecological flow requirements, aiming to maximize total hydropower generation while minimizing the ecological alteration degree.

Study Configuration

• Spatial Scale: Lower reaches of the Yalong River Basin, China, focusing on five cascade hydropower stations: Jinping I (JY), Jinping II (JE), Guandi (GD), Ertan (ET), and Tongzilin (TZL).
• Temporal Scale:
  • Historical runoff data: Jinping I Reservoir (1960–2016), Ertan Reservoir (1954–2017).
  • Natural baseline for ecological flow calculation: 1953–1992.
  • Scheduling period: Annual, divided into 36 ten-day intervals.
  • Hydrological year types analyzed: Wet (precipitation frequency P = 25%), Normal (P = 50%), and Dry (P = 75%).

Methodology and Data

• Models used:
  • Hydrological change detection: Mann-Kendall test, Moving T-test, Ordered Clustering method.
  • Ecological water demand calculation: Improved Ten-day Frequency Method (ITFM), validated by the Tennant method.
  • Multi-objective optimization: Non-dominated Sorting Genetic Algorithm II (NSGA-II).
  • Ecological alteration quantification: Lance distance (defined as Ecological Alteration Degree, EAD).
  • Optimal scheme selection: Knee point analysis (based on curvature calculation).
  • Parameter sensitivity analysis: Morris screening.
• Data sources:
  • Long-term historical runoff data from Jinping I and Ertan Reservoirs.
  • Characteristic parameters of the five cascade reservoirs.
  • Historical hydrological disturbance records of the Yalong River Basin.

Main Results

• The hydrological change point in the lower Yalong River Basin was identified as 1992, primarily attributed to large-scale human activities (dam construction), with the period 1953–1992 selected as the natural baseline for ecological flow calculations.
• Suitable ecological water demand for the Jinping I and Ertan reservoirs consistently increases from late May to mid-July, peaking between July and September.
• A significant inverse trade-off exists between cascade hydropower generation (CHG) and ecological alteration degree (EAD), with this trade-off being more sensitive (steeper gradient) in dry years due to intensified water scarcity.
• Compared to conventional scheduling, the proposed ecological-prioritizing scheme (S3) achieved substantial reductions in ecological alteration degrees: 37.74% in wet years, 19.84% in normal years, and 58.6% in dry years.
• The ecological-prioritizing scheme (S3) incurred a slight hydropower generation loss of 4.29% in wet years but delivered higher power output (3.57% in normal years and 6.53% in dry years) relative to the conventional scheme.
• The ecological flow compliance rate for the ecological-prioritizing scheme was consistently maintained above 65% across all hydrological scenarios.

Contributions

• Developed and validated an integrated framework for ecological scheduling of cascade reservoirs, combining hydrological alteration analysis, ecological flow calculation, and multi-objective optimal scheduling.
• Accurately identified the hydrological change point in the Yalong River Basin using a comprehensive multi-method approach, establishing a robust natural baseline for ecological flow assessment.
• Introduced and applied the Lance distance as a quantitative metric for ecological alteration degree, effectively measuring the deviation between actual discharge and suitable ecological water demand.
• Demonstrated the effectiveness and robustness of the NSGA-II algorithm for balancing conflicting objectives (hydropower generation and ecological protection) in complex, monsoon-influenced cascade reservoir systems.
• Provided a valuable and adaptable technical framework and decision-making reference for reconciling hydropower development with downstream ecological water use in similar river basins globally.

Funding

• Open Fund of the State Key Laboratory of Hydraulics and Mountain River Development and Conservation, Sichuan University (No. SKHL2321).
• Sichuan Provincial Regional Innovation Cooperation Program (No. 2025YFHZ0281).
• Science and Technology Projects of Xizang Autonomous Region, China (No. XZ202401ZR0124).

Citation

@article{Li2026Optimization,
  author = {Li, Ji-Dong and Zhang, Shuo and Xiao, Gui-You and Xi, Fu and Lei, Ming and Huang, Wei-Bin and Liang, Chu-Sheng and zhan, Yang},
  title = {Optimization scheduling of cascade reservoirs under an ecological approach: a case study},
  journal = {Scientific Reports},
  year = {2026},
  doi = {10.1038/s41598-026-70595-2},
  url = {https://doi.org/10.1038/s41598-026-70595-2}
}