By using the yearly data of water - sand that is gotten by a couple of adjacent hydrologic station in yellow river lower reaches , this paper makes use of kinds of math methods looking for the nonlinear disturbance among all of the factors , and introduces the thinking of analysis , logic , conclusion , inference , and random to nonlinear hydrologic forecasting . it realizes the valid approximation of the water level process in erodible - bed channel 本文選擇黃河下游兩對相鄰水文站多年水沙資料,借助多種數(shù)學方法尋找其中的非線性擾動項,將隨機數(shù)學中分析、邏輯、歸納、演繹、隨機的思考問題方式引入到非線性水文預報中,實現(xiàn)沖淤河道相應水位過程的有效擬合。