【目的】三峡水库可以有效应对长江中下游流域特大干旱,但其抗旱补水效果的定量评估仍存在不足。本研究旨在定量分析三峡水库补水对中下游干流水位和流量的调控作用,为科学评估其抗旱效益提供理论依据。【方法】基于2020—2022年三峡水库出入库流量及长江中下游干流逐日水位、流量数据,构建一维水动力模型,开展三峡水库对长江中下游干流的补水作用研究。【结果】①一维水动力模型验证表明,长江中下游各断面水位和流量模拟精度较高[R²>0.97,纳什效率系数(NSE)大于0.77,百分比偏差绝对值|PBIAS|小于7%],可以用于长江中下游干流抗旱补水作用研究。②补水作用分析表明,三峡水库抗旱补水对沙市至汉口段的水位提升效果最为显著,但随着距离增加呈现明显的衰减趋势。如以三峡下泄流量为5 000 m³/s为例,补水流量为3 000 m³/s时,沙市站流量与水位增幅分别为2 018 m³/s和1.03 m,至汉口站降为895 m³/s和0.40 m,九江和大通站则进一步降至645 m³/s和0.34 m、536 m³/s和0.16 m。③2022年8、9月三峡水库2次抗旱补水调度分别向中下游补水8.3亿m³和6.8亿m³。其中,沙市至汉口段受益显著,如第2次补水调度,沙市站断面累积补水6.42亿m³,延迟石首水厂断水6 d;螺山站断面累积补水5.74亿m³,延迟潘湾水厂断水5 d;而汉口站以下河段则以流量补充为主,大通站累积补水量为3~4亿m³,这对保障其10 000 m³/s的最小生态流量具有重要作用。【结论】三峡水库抗旱补水调度对中下游干旱具有显著改善作用。建议沙市—汉口河段以水位调控为主导策略,汉口以下河段实施流量控制[重点保障大通站10 000 m³/s(最小生态流量阈值)],并根据不同断面的不同时期用水需求,实施分异化补水方案,从而提升整体生态补水效益。

【Objective】While the Three Gorges Reservoir (TGR) plays a crucial role in mitigating extreme droughts in the middle and lower Yangtze River basin, quantitative assessments of its drought-relief water supplementation effects remain insufficient. This study aims to quantitatively analyze the regulatory effects of the Three Gorges Reservoir’s water supplementation on water levels and discharge in the mainstem of the middle and lower reaches, providing theoretical basis for scientific evaluation of drought mitigation benefits.【Method】Utilizing daily water level and discharge data from the TGR and the middle-lower Yangtze River between 2020 and 2022, a one-dimensional hydrodynamic model was employed to analyze the water replenishment effects of the TGR on the downstream reaches.【Result】(1)Model validation confirmed high simulation accuracy for all study sections, demonstrating its reliability for drought mitigation studies. (2) Water supplementation analysis revealed that maximum water level increases in the Shashi-Hankou reach, with progressive downstream attenuation. When the TGR maintained a discharge of 5 000 m³/s with a supplementation flow of 3 000 m³/s, the Shashi station showed increases of 2 018 m³/s in discharge and 1.03 m in water level. These effects decreased to 895 m³/s and 0.40 m at Hankou station, further declined to 645 m³/s and 0.34 m, 536 m³/s and 0.16 m at Jiujiang and Datong stations, respectively. (3) During August and September 2022, two drought-relief water supplementation operations released 830 million m³ and 680 million m³ of water, respectively. The Shashi-Hankou reach benefited substantially: in the second operation, Shashi station received a cumulative supplementation of 642 million m³, delaying water cutoff at Shishou waterworks by 6 days, while Luoshan station received 574 million m³, postponing Panwan waterworks’ cutoff by 5 days. Downstream of Hankou, flow augmentation predominated, with Datong station accumulating 300 million to 400 million m³ of supplemented water, crucial for maintaining its 10 000 m³/s minimum ecological flow threshold.【Conclusion】The drought-mitigation water supplementation operations from the TGR significantly alleviated drought conditions in the middle and lower reaches. We propose implementing differentiated regulation strategies. water-level-oriented regulation for the Shashi-Hankou reach, and discharge-focused control for downstream sections (with particular emphasis on maintaining the minimum ecological flow threshold of 10 000 m³/s at Datong station). These strategies should be complemented by section-specific water supplementation schemes tailored to the temporal water demand variations at different cross-sections, thereby optimizing the overall ecological benefits of water supplementation.