Application of the synthetic unit‐graph in the western mountain states

Abstract

In 1938 F. F SNYDER [see 1 of “References” at end of paper] presented a method for synthesizing unit‐hydrographs for any basin from certain physical measurements of the basin. The writer has found the procedure to be a very convenient tool in the solution of many hydrologic problems for which approximate unit‐hydrographs are necessary. The equations and constants, presented by Snyder were developed from data for streams in the Appalachian Highlands. During the past year the writer, engaged in developing river‐forecasting methods for the Sacramento and Lower San Joaquin rivers in California, has had occasion to note that some changes in the procedure are necessary before it can be applied to streams of that area. This paper presents the results of an investigation to determine the necessary adjustments for Snyder's methods in order to make them most effective for use in the basins of the Sierra Nevada and Coast Range. Although this investigation was conducted with the thought that Snyder's method could be adapted to meet the different conditions, the possibility that an entirely different approach might prove more satisfactory was not neglected. It developed that an adaptation of the original method gave only slightly less reliable results than did an entirely different, more complicated, and no more logical solution. It is felt that the simplification gained by adhering to the one procedure far outweighs the minor gain in accuracy through a major change in method.