基于Copula函数的梯级水库设计洪水地区 组成研究

Abstract

目前工程设计中常用的同频率地区组成带有一定的人为性，统计理论基础不足。利用Copula函数推导了两种考虑空间相关性的梯级水库设计洪水地区组成，即条件期望组成和最可能组成。以清江流域为例，对三种地区组成进行比较研究，分析了上游水布垭-隔河岩梯级水库的调蓄对高坝洲断面设计洪水的影响。结果表明：同频率组成计算的设计结果系统偏小，可能会增加设计断面的防洪风险。基于Copula函数的两种组成充分考虑了各分区洪水的随机性和空间相关性，设计成果比较合理。受上游梯级水库调蓄的影响，高坝洲断面千年一遇设计洪水的削峰率为40%左右。 The equivalent frequency regional composition method is widely used in practice. However, this method is based on artificial hypothesis and lacks the statistical basis. Two statistical composition methods, i.e. the conditional expectation method and the most likely method are proposed and derived based on Copula function. The Qingjiang cascade reservoirs are selected as the case study and the impact of Shuibuya-Geheyan cascade reservoirs regulation on the design flood of Gaobazhou dam site is analyzed. It is demonstrated that the results of equivalent frequency method are systematically smaller than those of the two proposed methods, which may lead to increasing the hydrological estimation risk. The proposed methods with strong statistical basis can capture the spatial correlation of flood events for each contributing watershed area, and the estimated design flood values are more reasonable than those of the equivalent frequency method. The 1000-year design peak discharge at Gaobazhou dam site has been cut about 40% due to the regulation of upstream cascade reservoirs.