2020年8月,受长江上游强降雨影响,岷江、沱江、涪江发生了大洪水或特大洪水。在长江上游水库群全力拦洪、削峰、错峰调度后,长江上游干流朱沱至寸滩江段仍出现超保证洪水,给川渝河段带来巨大的防洪压力。重点从暴雨洪水概况、金沙江水库群调度过程、还原计算等方面对“20·8”洪水展开深入研究,量化分析金沙江水库群调度对川渝河段的防洪作用。研究结果表明:金沙江水库群在长江4号、5号洪水期间共拦蓄洪量47.37亿m³,占寸滩以上水库群总拦蓄量的57.7%,成功实现与嘉岷流域的洪水错峰调度,削减了川渝河段洪峰流量9 400~11 700 m³/s,降低川渝河段洪峰水位2.6~2.8 m,避免了上游干流全线超保证水位,降低寸滩站洪峰水位约2.6 m,占其洪峰水位总削减值近9成,有效减轻了防洪压力。

In August 2020, Minjiang River, Tuojiang River and Fujiang River saw great or catastrophic floods brought about by heavy rainfalls in the upper reaches of the Yangtze River. Although the reservoir group in the upper reaches of the Yangtze River has been fully involved in the flood control, peak reduction and peak shifting, floods above safety water level still hit the Zhutuo-Cuntan segment of the mainstream in the upper reach of the Yangtze River, posing huge flood control pressure to Sichuan-Chongqing reach. We quantified the benefits of operating the Jinsha River reservoir group to the flood control of Sichuan-Chongqing reach by investigating in-depth the floods in August 2020 from aspects of the overview of storm flood, the operation process of Jinsha River reservoir group, and the restoration calculation. Our findings demonstrated that the Jinsha River reservoir group had detained and impounded 4.737 billion m³ of water during the Yangtze River No.4 and No.5 floods, accounting for 57.7% of the total water detention by reservoir groups upstream of Cuntan, together with the successful peak shifting along the Jialing River and Minjiang River basins. It had also prevented the whole upper mainstream from exceeding safety water level by reducing the peak discharge and water level in Sichuan-Chongqing reach by 9 400-11 700 m³/s and 2.6-2.8 m respectively, and furthermore effectively relieved the flood control pressure by cutting the flood peak water level at Cuntan by about 2.6 m, equivalent to nearly 90% of the total reduction of peak water level.