Using instream water temperature forecasts for fisheries management: an application in the Pacific northwest

Water temperature is an important factor affecting aquatic life within the stream environment.
Cold water species, such as salmonids, are particularly susceptible to elevated water temperatures. This paper
examines the potential usefulness of short-term (7 to 10 days) water temperature forecasts for salmonid management.
Forecasts may be valuable if they allow the water resource manager to make better water allocation
decisions. This study considers two applications: water releases from Lewiston Dam for management of adult
Chinook salmon (Oncorhynchus tshawytscha) in the Klamath River and leasing water from agriculture for management
of steelhead trout (Oncorhynchus mykiss) in the John Day River. We incorporate biophysical models
and water temperature distribution data into a Bayesian framework to simulate changes in fish populations and
the corresponding opportunity cost of water under different levels of temperature forecast reliability. Simulation
results indicate that use of the forecasts results in increased fish production and that marginal costs decline as
forecast reliability increases, suggesting that provision and use of such stream temperature forecasts would have
potential value to society.