The Analysis Of Water-sediment Relationship And The Stochastic Simulation Of Water-sediment Processes Based On Copula Functions

The sediment problem is an important factor affecting the exploitation and utilization of a river water energy resource.Due to the fact that water and sediment are associated with each other,the study of sediment problems must be considered in combination with the flow rate.Copula functions are widely used in the analysis of complex multivariate hydrological phenomena with the characteristics of flexible structure and wide applicability.In this paper,Copula functions were used to study multivariate frequency analysis and the stochastic simulation of water and sediment.The joint distributions of peak discharge-sediment,volume-sediment and peak-volume-sediment were established through copulas firstly.The joint OR probability and the joint OR return period,the conditional probability and the conditional period,the joint AND probability and the joint AND return period were calculated based on the joint distributions.And then,a stochastic simulation method of sediment concentration was proposed based on the Copula functions with considering the effect of flow on sediment concentration after the stochastic simulation of daily flow.The results showed that,the trivariate joint OR return period was less than the brivariate and univariate one.And the trivariate AND return period was larger than the brivariate and univariate one.Which showed that the three-dimensional Copula function took into account the influence of more flood variables on the sediment and could better reflect the impact of the flood process on the sediment peak.In addition,compared with the stochastic simulation of sediment concentration by using the model of AR(1),the stochastic simulation of sediment concentration based on Copula function was closer to the measured sequences.Therefore,the analysis of water-sediment relationship and the stochastic simulation of water-sediment processes based on Copula functions was effective,which could provide theoretical basis and technical support for the regulation of runoff and sediment in the basin.