Snowmelt runoff simulation using a degree-day and nonlinear multiple recession model

A snowmelt runoff model was developed using (a) the degree-day method and (b) a nonlinear multiple recession equation. The nonelinear multiple recession equation was derived using the concepts of superimposition and three nonlinear sequential recessions. The developed equation is infinite and nonlinear, and accounts for delay and attenuation of the runoff process. The derived equation simulates the total runoff hydrograph without separating the runoff into a number of runoff components. For snowmelt estimation, the degree-day factor is determined using computed and observed snow cover data. The model was applied to the Snake River basin above Heise (14,900 km2) for eleven snowmelt seasons. The average volumetric difference between computed and the observed runoff was within one percent and R square was 0.91. The model appears to be effective for operational snowmelt runoff forecastiang as the timing of low and high runoff matches the observed.