Base flow as a parameter in forecasting April-June runoff

A preliminary analysis using base flow of the preceding fall as a parameter in forecasting snowmelt runoff during April - June period for major tributaries to the Columbia River is presented. Three separate forecasting formulas were developed for each stream; first, using water content with April - June flow; second, using April 1 water content and November 1 base flow with April - June flow; and third, adding April precipitation. Statistical parameters for the 12 equations are tabulated and discussed. Base flow was found to be highly significant. April precipitation is not significant especially when it must be estimated for the April first forecast. In basins of low elevation headwater precipitation carried more weight. Base flow proved to be an integrating factor of difficult to measure variables, evapotranspiration, soil moisture and groundwater storage.