Snow survey versus winter precipitation for forecasting runoff of the Tuolumne River, California

The relative accuracy of snow survey and winter precipitation data as applied to forecasting the spring and summer runoff of a typical Sierra Nevada western-slope river was investigated. Fifteen years of snow survey data were available, and the same period of precipitation records were used in the comparison. It was obvious on examination of the graphs that several years (4 in the case of snow survey and 3 in the case of precipitation) were much out of harmony with all other years. Justification for these discrepancies was found; they were usually caused by abnormal fall or spring precipitation. These years with abnormal precipitation were omitted in determining the position of the line on the graph showing the relationship of winter precipitation on the water equivalent of snow to stream flow. The conclusion is in favor on snow survey data.