New method for measuring water seepage through salmon spawning gravel.

A new method, with heat as a tracer, was developed for measuring rate and direction of intragravel waterflow through salmon spawning gravel. A commercial flowmeter was calibrated in the laboratory under controlled environmental conditions. Flow measurements comparing the flowmeter with a dye-tracer method were made in an artificial stream channel at Young Bay and in two low-gradient streams at Trap Bay in southeast Alaska. The method requires a standpipe. Once the standpipe is in place, a flow reading can be taken in 3 to 5 minutes. The flowmeter response is linear for flow rates up to 150 centimeters per hour and then becomes curvilinear. A correction factor applied to the instrument response can extend the range to about 500 centimeters per hour. The flowmeter demonstrated excellent reproducibility in the laboratory. The equipment is self-contained, and all necessary supplies are available on the open market.