“20·8”与“81·7”长江上游暴雨洪水特征对比分析

Comparative analysis on rainstorm flood characteristics in August 2020 and July 1981 in upper reaches of Changjiang River

2020年8月,长江上游嘉陵江、岷沱江流域发生大范围暴雨过程,长江上游干支流洪水并发,遭遇严重,寸滩站出现有实测记录以来的第二高洪水位,三峡水库出现建库以来最大洪水(以下简称“20·8”洪水)。为提高对长江上游暴雨洪水规律的认识,将“20·8”洪水与历史上1981年7月(以下简称“81·7”洪水)长江上游型大洪水的暴雨洪水特征进行较全面的对比分析。结果表明:①两次长江上游暴雨洪水特征存在一定的异同点;②两次致洪暴雨过程持续时间均较长(6~7 d),暴雨强度大,范围广,主雨带位置主要出现在金沙江中下游、岷沱江至嘉陵江一线,且暴雨中心相对集中;③相应发生的长江上游大洪水主要由岷沱江、嘉陵江来水与干流底水遭遇形成;④“81·7”洪水过程尖瘦、涨水历时短、洪峰流量更大、洪峰稀遇程度高于洪量,“20·8”则呈现为复式洪峰、洪水过程肥胖、受人类活动影响较大、洪峰水位更高等特点。

In August 2020,a large-scale heavy rainfall occurred in the Jialing River,Minjiang River and Tuojiang River basins in the upper reaches of Changjiang River,and the flood occurred in the main stream and tributaries of the upper reaches of Changjiang River,and the flood control situation was severe.The second highest flood level was recorded in Cuntan station,and the largest flood occurred since the construction of the Three Gorges Reservoir(hereinafter referred to as"20·8"flood).In order to improve the understanding of the rainstorm flood,the characteristics of the“20·8”and“81·7”flood events are compared and analyzed comprehensively.The results showed that:①There were some similarities and differences in the characteristics of the two rainstorm floods.②The flood-causing rainstorm process lasted generally 6~7 days,and the rainstorm intensity was large and the range was wide.The main rain belt mainly occured in the middle and lower reaches of Jinsha River to Minjiang River,Tuojiang River and Jialingjiang River,and the rainstorm center was relatively concentrated.③The corresponding major floods in the upper reaches of Changjiang River were mainly formed by the encounter of incoming water of the Minjiang River,the Tuojiang River and the Jialing River and the baseflow of the main stream.④The"81·7"flood process curve was thin,the flood duration was short,the flood peak discharge was larger,and the rare degree of flood peak was higher than that of flood volume.The"20·8"flood was characterized by double flood peak,obesity flood process,higher flood peak water level and being greatly affected by human activities.