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基于两变量分析方法推求分期设计洪水,对于给定的联合重现期水平,存在着多种洪水组合均可满足规定的防洪标准,现有方法无法评价不同组合发生的可能性和合理性.采用归一化的联合概率密度函数值作为洪水发生的相对可能性指标,提出了分期设计洪水组合的可行区间,并基于条件概率原理推导了3种具有统计意义的联合重现期水平下的计算公式,即最可能组合、条件最可能组合和条件期望组合.丹江口水库应用结果表明:以7日洪量为例,最可能组合和条件最可能组合的估计值均位于可行区间内,条件期望组合的估计值在可行区间外.建议采用条件最可能组合方法计算丹江口水库7日洪量分期洪水设计值,该法不仅具有较强的统计理论基础,而且能够较好地描述汛期洪水特征;在满足防洪标准的前提下,通过适当抬高(降低)夏(秋)汛期的洪水设计值,有利于水库汛末蓄水和提高综合利用效益.
Based on the two-variable analysis method, it is deduced that the staged design flooding, for a given combined recurrence level, there are many flood combinations that can meet the required flood control standards, and the existing methods can not evaluate the possibility and rationality of different combinations. The normalized joint probability density function is regarded as the relative possibility indicator of flood occurrence, and the feasible interval of staged design flood combination is proposed. Based on the conditional probability theory, three statistical formulas with statistical significance at the combined recurrence level are derived , That is, the most likely combination, the most likely combination of conditions and the combination of conditional expectation.The application of Danjiangkou Reservoir shows that the estimated maximum possible combination and the most likely combination of conditions are all within the feasible range based on the 7-day flood amount, and the estimation of conditional expectation combination The value is outside the feasible interval.It is suggested to calculate the design flood discharge value of Danjiangkou reservoir on the 7th by the most probable combination method.The method not only has a strong statistical theory foundation but also can well describe the flood characteristics of flood season; Under the precondition, by properly raising (reducing) the flood design value in summer (autumn) flood season, it is beneficial to the end of flood season And improve the utilization efficiency.