为探究洪水不确定性对大坝防洪特征水位设计的影响,采用水库调洪演算的随机微分方程推求防洪特征水位的概率分布线型,以三峡水库为例,通过调洪演算将洪水不确定性转换为防洪特征水位的不确定性,以分析已建水库防洪特征水位的分布规律,并对三峡水库防洪特征水位进行了复核分析。研究结果表明:随着样本容量的增加,洪水的信息量增大,三峡大坝设计资料和原校核洪水位(180.4 m)的可靠度均有所提高;当样本容量为120 a时,设计洪水资料和原校核洪水位的可靠度分别为93.19%和99.17%。研究结果为提高水库大坝安全设计提供了理论依据。

In order to explore the influence of uncertainty of flood on design of characteristic flood level for dam, we derive probability distribution of characteristic flood level (CFL) for dam by using stochastic differential equation for calculation of flood regulation. Three Gorges reservoir is selected as a case study. The uncertainty of flood is transformed into that of CFL so as to analyze probability distribution of CFL through calculation of flood regulation. On this basis, we recheck the CFL of Three Gorges reservoir. The results show that, 1) reliabilities of design flood data and original exceptional flood level (180.4 m) increase with the increase of sample size; 2) under sample size of 120a, reliability of design flood data and reliability of CFL are 93.19% and 99.17%, respectively. Finally, the research results provide theoretical basis for improvement in safety design of dam reservoir.