采用Gumbel 逻辑模型建立基于超定量取样的两变量联合分布，利用所建立的联合分布，给出了条件频率和两种两变量重现期的计算方法。以隔 河岩水库坝址洪水研究为例，分析了当洪峰超过其某一频率的设计值时，各不同频率的设计 洪量发生的条件频率，并对同频率设计值组合的两变量重现期进行了计算。研究表明在推求 设计洪水过程线时，洪峰和洪量同频率的假定并不是过于偏保守，甚至还存在一定的风险， 作为设计方法中的假定，具有一定的合理性。

The Gumbel logistic model is used to describe the dependent structure between the flood peak and flood volume and a bivariate joint distribution of peak-volume using PDS sample approach is deve loped. Based on the derived bivariate distribution, the approaches for calculating conditional frequency and bivariate return period are presented. The Geheyan reservoir is selected as a case study. The assumption that the peak and volume adopt a same frequency in design flood hydrograph is discussed through the conditional frequency of flood volume given flood peak exceeding a flood quantity with a specified frequency. The bivariate return periods of design values for peak and volume in pairs derived from univariate distribution respectively are estimated. The results of the study show that the assumption is not considered to be very conservative but rational in a certain extent.