Biological Component

Water Resources of Idaho

Biological Component

Environmental variables, with a focus on stream temperature, and benthic invertebrate and fish assemblages were evaluated for 34 least-disturbed, wadeable, second-through fifth-order streams in the Salmon River Basin, Idaho, during July through September 2001. Data were collected to document the thermal regime of least-disturbed streams, characterize the distribution of aquatic biota in streams representing a gradient of temperature, and describe the relations between the environmental variables and the benthic invertebrate and fish assemblages. Comparison of nine stream temperature metrics with the U.S. Environmental Protection Agency's stream temperature criterion showed that temperature at 33 sites where stream temperature data were collected exceeded the 10 degree Celsius maximum weekly-maximum temperature criterion for bull trout (Salvelinus confluentus) spawning and juvenile rearing. Temperatures at 91% (30 of 33) of the sites exceeded the Idaho Department of Environmental Quality's 13 degree Celsius maximum daily-maximum temperature criterion for the protection of salmonid spawning; temperature at 33 sites exceeded the 9 degree Celsius maximum daily-average temperature criterion. The thermal regime at most sites did not exceed the IDEQ criteria for the protection of coldwater biota. Nine environmental variables (water-surface gradient, discharge, wetted channel width, width:depth ratio, aspect, total seasonal thermal input, open canopy, riparian canopy density, and elevation) were selected for comparison with the nine stream temperature metrics. Elevation showed the strongest inverse correlation with the stream temperature metrics.

Two hundred-one benthic invertebrate taxa from the 34 sampling sites were identified. The most abundant taxa were Baetis tricaudatus, Oligochaeta, Tvetenia bavarica group, Acari, Rhithrogena, Cinygmula, Heterlimnius, Micropsectra, Eukiefferiella devonica group, Drunella doddsi, and Cricotopus. Among the invertebrate taxa collected, 32 were identified as coldwater taxa.

Ten species of fish in the families Salmonidae, Cottidae, and Cyprinidae were collected. Two species (bull trout and chinook salmon) listed as threatened under the U.S. Fish and Wildlife Service Endangered Species Act were collected. Among all species, correlation between relative fish abundance and stream temperature metrics indicated that bull trout had the strongest inverse correlation with stream temperature. Bull trout and juvenile bull trout (less than 150 millimeters in length) densities were inversely correlated with stream temperature. On the basis of a logistic regression model developed during this study, juvenile bull trout occurrence and maximum daily-maximum temperature were significantly correlated. However, results from this model differed from results of a similar model developed by the U.S. Forest Service on the basis of regional data collected in the Pacific Northwest. The regression model based on data collected during this study showed higher probabilities of occurrence of bull trout at colder stream temperatures (10-15 degrees Celsius) and lower probablitites of occurrence at warmer stream temperatures (16-21 degrees Celsius). The model comparisons suggest that regional or local differences need to be considered when deriving stream temperature criteria.

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Project Data

Interactive map of the study area
Select one of the three options for the Stream Temperature Study on this page. This will open the interactive map in a separate window. The map shows monitoring sites in the study. Tools on the top of the map can be used to do such things as Identify, Query and Print. To download a site's information on fish data or invertebrate data use the hyperlink tool after making that layer active.
Download delimited text files containing 2001 temperature data
Download delimited text files containing invertebrate data

For further information on this study please contact Doug Ott - (208)387-1335 - or email dott@usgs.gov.

Stream Temperature Information

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