Watershed groups, individuals, and land management and regulatory agencies are collecting stream-temperature data in order to understand, protect and enhance cold-water fisheries. While great quantities of data are being generated, its analysis and interpretation are often not adequate to identify stream reaches that are gaining or losing temperature, or to correlate temperature changes with factors such as vegetative canopy cover or stream-flow levels. We use a case study from the Lassen and Willow creek watersheds in northeastern Modoc County to demonstrate graphical methods for displaying, analyzing and interpreting stream-temperature data.

Declines in cold-water habitat and fisheries have generated stream-?temperature monitoring efforts across Northern California and the western United States. We demonstrate a statistical analysis approach to facilitate the interpretation and application of these data sets to achieve monitoring objectives. Specifically, we used data collected from the Willow and Lassen creek watersheds in Modoc County to demonstrate a method for identifying and quantifying potential relationships between stream temperature and factors such as stream flow, canopy cover and air temperature. Our monitoring data clearly indicated that a combination of management practices to increase both in-stream flow and canopy cover can be expected to reduce stream temperature on the watersheds studied.