基于Copula函数的三峡库区万州段蓄水前后降雨径流关系分析

Study on the relationship of rainfall-runoff before and after impoundment of the Three Gorges Reservoir based on copula function in the Wanzhou City

基于万县水文站的降雨-径流实测资料,引入Copula函数模型,定量分析蓄水过程对降雨-径流的影响规律。研究表明:Copula联合分布模型能较好地模拟不同阶段的降雨-径流关系。蓄水前降雨和径流均满足皮尔逊Ⅲ型分布。施工期和初步蓄水阶段,降雨和径流分别为Gumbel分布和对数正态分布。试验性蓄水阶段的降雨为对数正态分布,径流恢复到皮尔逊Ⅲ型分布。施工期及初步蓄水阶段较蓄水前的降雨量和径流量均减少,变幅区间分别减少38.4%和20.6%。试验性蓄水阶段年降雨量增大,变幅区间增加24.5%,而年径流量减少,变幅区间减少57%。研究成果可对三峡库区水资源开发利用具有一定的参考价值。

According to the observed data of rainfall and runoff at Wanxian Hydrological Station,the influence of water storage process on rainfall-runoff relationship was quantitatively analyzed by Copula function model.The results show that Copula joint distribution model can simulate the rainfall-runoff relationship better at different stages.The distribution of rainfall-runoff before impoundment shows a PearsonⅢdistribution.During construction period and initial storage period,rainfall and runoff satisfy Gumbel distribution and logarithmic normal distribution,respectively.In the experimental storage stage,the rainfall is logarithmic normal distribution,and the runoff returns to PearsonⅢdistribution.Rainfall and runoff during construction and preliminary impoundment stages were reduced compared with those before impoundment.The range of variation is reduced by 38.4%and 20.6%respectively.In the experimental storage stage,the annual rainfall increased,the variation range increased by 24.5%,while the annual runoff decreased,and the variation range decreased by 57%.The model can also predict the extreme annual runoff and rainfall in the reservoir area.