三峡大坝建设前后对长江上游径流联合分布影响的分析

Influence of Three Gorges Dam construction on runoff distribution in the upper reaches of the Yangtze River

以三峡工程蓄水运行的2003年为分界点,利用长江上游流域寸滩、武隆、宜昌3站1951-2016年的月径流资料,利用Copula函数,定量分析了三峡水库蓄水前后对长江上游多站径流的联合分布的影响.研究结果表明:1)三峡水库建设前后,无论2个还是3个站的径流联合分布均发生了变化.其中,寸滩–宜昌2站联合分布没有变化,但分布函数的参数略有减小;武隆–宜昌的联合分布从Gaussian Copula转变为Gumble Copula型;寸滩–武隆–宜昌的3站联合分布由Gumble Copula变成Gaussian Copula型. 2)三峡建库后,在相同的概率水平下,3站对应的径流量均比建库前明显减少;在相同重现期下,3站对应的径流量同样比建库前明显减少,其中,宜昌站径流减小率最大,寸滩次之,武隆最小.这表明三峡建库后,对坝下宜昌站径流的影响高于三峡大坝上游的寸滩、武隆2站.

Monthly runoff data at Cuntan,Wulong and Yichang stations in the upper reaches of the Yangtze River from 1951-2016,and Copula function were used to analyze quantitatively impact of Three Gorges Reservoir on joint distribution of runoff from multiple stations in the upper reaches of the Yangtze River before and after impoundments.It was found that after construction of the Three Gorges Reservoir,joint distribution of runoff changed at some stations.Joint distribution at Cuntan and Yichang stations did not change,but the parameters of distribution function decreased slightly.Joint distribution at Wulong and Yichang changed from Gaussian Copula to Gumble Copula type.Joint distribution at Cuntan,Wulong and Yichang changed from Gumble Copula to Gaussian Copula type.After construction of the reservoir,runoff at these three stations was significantly reduced at similar probability level.Corresponding runoff at these three stations also decreased significantly in the same return period.Yichang station showed the largest runoff reduction rate,with Cuntan following,with Wulong the smallest.Three Gorges Reservoir therefore impacts runoff at downstream Yichang station higher than upstream Cuntan and Wulong stations.