Study On The Stochastic Concentration Model And Determination Of The Parameters Of Nash Model Based On Stochastic Theory

All stochastic factors in the flow concentration system are discussed. The flow concentration process is thought as a stochastic process influenced by both deterministic factors and stochastic factors.Nash flow concentration model with Gaussian white noise process is built by stochastic differential equations, and their analytic and numerical solution are given. To the stochastic characters of model parameters, the stochastic flow concentration model with deterministic input and stochastic parameters is built. Two solving methods are given for it. One is getting the PDF of discharge processes using Liouville law;the other is getting the stochastic S curve under the condition of unit input and model parameters obeying normal distribution and gamma distribution. The computing cases show that both the mean discharge process and variance process can be given for the stochastic flow concentration model.As for the linear stochastic flow concentration system, there are some theory relations among all moments of input, output and instantaneous unit hydrograph. According to this, the relationship between auto-correlation function of discharge process with white noise input and Markov noise input and Nash model parameters can be obtained, and Nash model parameters can be gotten only based on discharge data. The examination in Yanduhe basin and Xiangyang-Huangzhuang reach show that Nash model parameters of channel concentration are more reasonable when input process is Markov noise and Nash model parameters of basin concentration are more reasonable when input process is white noise. This conclusion is coincident with the stochastic structure characters of reach inflow processes and storm processes.