中文摘要：

对于传统的多变量分析方法,给定某一联合重现期,满足防洪标准的峰量组合形式有无数多种,但不同联合设计值得到的洪水过程线及水库最高调洪水位均存在较大的差异,如何在联合重现期水平下选取合理的设计值尤为关键。本文利用Copula函数建立洪峰与不同时段洪量的多变量联合分布,采用OR重现期作为防洪标准,联合概率密度函数值作为洪水发生相对可能性的度量指标;以满足防洪标准为约束条件,构建峰量最可能组合的通用模型,并通过拉格朗日乘数法进行求解。采用最可能组合方法分别计算了汉江流域丹江口水库的3维和4维最可能联合设计值,并与单变量同频率法、多变量同频率法设计值对比。结果表明：单变量同频率设计值达不到防洪标准,其假设洪峰与洪量完全相关,各个洪水特征量均采用单变量概率分布来描述,未能充分考虑各个特征量的内在相关性,并不符合汛期洪水发生的内在规律;最可能组合法与多变量同频率法相比,洪峰偏小,长历时洪量偏大,丹江口水库具有多年调节能力,洪量起主要作用,所以最可能组合法推求的设计洪水结果偏安全。峰量最可能设计值更符合丹江口水库的应用要求,因此,本文所提方法具有较强的统计基础,更加符合水文现象的内在规律,可用于水库设计洪水计算。

英文摘要：

For conventional multivariate frequency analysis methods,there are an infinite number of combinations of flood peaks and volumes satisfying the flood prevention standard under the given joint return period（ JRP）; however,different joint design values would lead to differences of flood hydrograph and maximal water level which occurs in reservoir routing. Hence,how to select reasonable design values under given JRP is very important. In this paper,the Copula functions were used to construct the multivariate joint distributions of flood peaks and volumes,and the OR JRP was adopted as flood prevention standard. The normalized joint probability density function value was adopted to measure the relative occurrence likelihood of flood events,and the general model of Most Likely Composition（ MLC） of flood peaks and volumes were established subject to the flood prevention standard. The Lagrange multiplier method was adopted to solve the model. The trivariate and four-dimension MLC design floods of Danjiangkou reservoir in Hanjiang basin were estimated using the proposed method,and the quantiles estimated by univariate identical frequency（ UIF） and multivariate identical frequency（ MIF） methods were compared with those calculated by MLC. The results indicated that the UIF estimations could not satisfy the flood prevention standard; the UIF method assumed that the flood peak is fully dependent upon the flood volume and all the variables are characterized based on univariate distributions. The UIF method cannot take the correlations of hydrologic variables into consideration,and it does not satisfy the inherent rule of flood events. It is also indicated that the MLC method had a smaller flood peak and larger long-duration volume than those by the MIF method. The Danjiangkou reservoir has the capacity of multi-year regulation and the flood volumes are mainly responsible for flood prevention safety,and thus the MLC estimation values are safer. The joint design values of MLC method are more rational according to