The hydrology of four streams in western Washington as related to several Pacific salmon species

Abstract

Enhancement-or possibly even preservation-of the Pacific salmon hinges on the careful planning and proper management of the streamflow upon which they depend for spawning. Most spawning activity occurs on reaches of streams where specific hydraulic conditions exist and where stream-channel characteristics and water-quality criteria are met. The present report is the first of a series and is used to present the method of determining preferred spawning conditions and results of the investigation of 129 measurements on 14 study reaches of the Dewatto, Cedar, Kalama, and North 'Fork Nooksack Rivers. Subsequent reports, using the same method will present analyses and preferred spawning and rearing discharges for other streams used by salmon. The method consists of measuring water depth and velocities to designate, from area-(spawnable) discharge curves, peak, preferred spawning discharges for fall chinook, spring chinook, sockeye, and coho salmon at each reach on each river. Also, streambed gravels, water temperature, suspended sediment, dissolved oxygen, and specific conductance are used to help evaluate river conditions during spawning. In examining the repeatability of the method, tested by analyzing independently each of selected pairs of adjacent reaches on the Cedar River, it was found that the preferred peak discharges from the comparisons varied 4.6 percent for the average of four species and two pairs of reaches. Peak spawning discharges ranged, for the four salmon species on each of the three study reaches of each river, from 50 to 140 cfs (cubic feet per second) on Dewatto River, from 230 to 510 cfs on Cedar River, from 245 to 800 cfs on Kalama River, and from 195 to 710 cfs on North Fork Nooksack River. The results indicate that the methods used and the probable discharge values determined are reasonable and, if economically justified, may be used to select discharges, for salmon spawning and rearing.