Storage Requirements for Northwestern Streams

Abstract

The method developed by the late Allen Hazen for determining storage requirements of streams for varying drafts has not been widely used by other engineers and the present paper is to call attention to some of its advantages by presenting some preliminary data on streams in Washington and Oregon. The writer desires to present these data for the further reason that Hazen's estimates concerning the streams of these two states are too conservative. His method of study, however, calls attention to certain of the characteristics peculiar to stream flow in the Northwest concerning which little definite information has as yet been published. The method referred to is described by Hazen in the Manual of the American Water Works Association on Water Works Practice, pages 51 and 63 inclusive, and in the American Civil Engineers Handbook, 5th Edition, pages 1446 to 1452 inclusive. Briefly, it is a statistical study which consists of the determination of the mean annual flow of a stream for the period of record and the computation of a coefficient of variation to indicate the variability of the stream from the mean. These are the two most important characteristics of any stream, viz., its mean annual flow and the manner in which it varies from that mean.