the problem of snow in determining the spillway design flood

Hydrographs from rain and from snow are combined to produce the design-flood hydrograph which is essential in determining the required capacity of the spillway of a dam. The rain flood is derived from a hypothetical storm in the basin. The snow hydrograph was derived by plotting the cumulative values of degree-days against cfs days in the form of a double mass curve. A lag of 3 days between temperature and runoff produce the smoothest curve. Runoff periods beginning and ending with the same temperature were selected, and the average slope of the mass curve for each period was determined. A degree-day factor was computed from the slopes. The degree-day factor was applied to a sequence of assumed temperatures to calculate the design snow-flood. The procedure is considered preliminary.