LUMPING PROCESS OF RUNOFF MODEL BASED ON EVALUATION OF ITS STOCHASTIC RESPONSE -DERIVATION OF HIGHER ORDER MOMENTS OF DISCHARGE-

Abstract

Using a runoff system composed of a hillslope runoff generation model and a channel network, this paper derives theoretical differential equations to calculate the first- to third-order central moments of discharge. Numerical simulation shows the results of cross-checking the validity of the derived equations. The results are as follows: σ_qi² and μ_qi3 , in a steady state are regarded as constant when the catchment area is smaller than one hundred and several tens kilometers square. The results of this study can be applicable to the evaluation method of lumping process of models based on their stochastic response characteristics.