应用Copula函数的潘家口水库设计洪水线推求

Flood Hydrograph Conculation by the Copula Function in Panjiakou Reservoir

传统单变量同频率洪水过程性设计将洪峰、洪量等特征参数进行单纯控制,忽视了洪水过程非线性联动机制。以潘家口水库历史洪水资料为依据,应用Copula函数构造洪水峰、量两变量联合分布,进而推求其边缘分布和最高水位线。结果表明,Copula能很好地考虑洪水过程的洪峰、洪量、历时、水位等参数间相关性进而实现联合分布模拟;且其面向整个设计洪水过程线而言的,其推求过程符合水文事件的多元非线性、随机性规律。另外,单变量同频率方法能够基本满足防洪标准,然而出于防洪安全和极端天气背景考虑,以两变量同频率组合设计洪水过程线更具合理性。

The traditional single-variable and same fi＇equeney flood process design simply controls the characteristic parameters such as Hong Feng and flood volume and neglects the nonlinear linkage mechanism of flood process. Based on the historical flood data of Panjiakou Reservoir, the Copula funetion is used to construct the flood peak and the joint distribution of two variables, and then the marginal distribution and the maximum water level are derived. The results show that Copula can well consider the correlation among Hong Feng, flood volume, duration, water level and other parameters of flood process, and then realize the joint distribution simulation, which is oriented to the whole design flood process line. The extrapolation process accords with the multivariate nonlinear and stochastic law of hydrological events. In addition, the single variable and frequeney method can basically meet the flood control standard. However, considering the background of flood control safety and extreme weather, it is more practical to design flood process line with the combination of two variables with the same frequeney.