基于Copula函数的洞庭湖流域水沙丰枯遭遇频率分析

受人类活动的影响,水沙灾害事件相继发生,对人们的生产、生活造成了威胁。以洞庭湖流域代表性水文站的年径流量和年输沙量系列数据为基础,应用P-III型曲线分别拟合并求得“松滋口、太平口、藕池口”三口入湖、“湘江、资江、沅水、澧水”四水入湖和城陵矶站出湖年径流量、年输沙量的边缘分布函数,再采用水文事件遭遇分析中广泛应用的Copula函数,建立洞庭湖流域水沙联合分布模型,分析洞庭湖流域水沙丰枯遭遇频率。研究结果表明洞庭湖三口、四水和城陵矶站的水沙丰枯遭遇频率关系与洞庭湖流域的水沙运动有密切联系,运用该水沙耦合模型可以为洞庭湖流域防洪减灾提供重要的理论依据。

Copula-based Probability Evaluation of Rich-Poor Runoff and Sediment Encounter in Dongting Lake Basin

Under the influences of human activities, the successive water and sediment disasters posed threats on people′s production and life. Based on the series data of annual runoff and sediment of representative hydrometric stations in Dongting Lake Basin, P-III distribution curve is applied to fit the marginal distribution of annual runoff and sediment of 3 inlets (Songzikou, Taipingkou, Ouchikou), four rivers (Xiangjiang River, Zijiang River, Yuanjiang River and Lishui River) (entering the lake) and Chenglingji (coming out of the lake). The application of popular Copula-constructed two-dimensional joint distribution of runoff and sediment was illustrated, and the joint distribution was used to calculate the encounter probability of rich-poor runoff and sediment in Dongting Lake Basin. Result shows that 1) Synchronous frequency of the runoff and sediment in 3 inlets is far more than asynchronous frequency, and the frequencies of rich water-rich sediment, poor water-poor sediment and normal water-normal sediment are equal basically. 2) Synchronous frequency of the runoff and sediment in four rivers and Chenglingji approximately equals asynchronous frequency, and the frequency of rich water-rich sediment is the highest in synchronous frequency, the frequency of poor water-poor sediment ranks the second, and the frequency of normal water-normal sediment is the lowest. 3) The frequency of the encounter of opposite status of runoff and sediment (the frequency of rich water-poor sediment and the frequency of poor water-rich sediment) is the lowest of the asynchronous frequencies of rich-poor runoff and sediment encounters in Chenglingji, 3 inlets and 4 rivers. The research results show that the model posses good evaluating performance and reveals a close contact with the basic characteristics of the runoff and sediment in Dongting Lake. With the analysis of the rich-poor runoff and sediment encounter probability, the frequency of water-sediment disasters can be understanding quantitatively, so the study can provide a technical guidance for the flood prevention and disaster reduction in Dongting Lake Basin.