Applying Reach Scale Data to Model Stream Temperature at the Watershed Scale

Stream temperature controls aquatic ecosystem function by directly influencing water quality, ecosystem productivity, and the physiological functioning of aquatic organisms.  To date, there are limited studies of the impacts of environmental disturbance on stream temperature, particularly on the eastern slopes of the Rocky Mountains. This region provides key habitat for native salmonid species such as westslope cutthroat trout (Oncorhynchus clarkii lewisi) and bull trout (Salvelinus confluentus), which are listed as ‘threatened’ and ‘species of special concern’, respectively.   Changes in stream temperature could limit habitat availability, reduce competitive advantage, and potentially increase mortality rates for these native species.  This study uses field data collected at high spatiotemporal resolution to develop a spatial stream temperature model that simulates the mass and energy balance of the stream system.  Preliminary field results demonstrate the high spatial and temporal variability in processes governing stream temperature in four study watersheds.  Groundwater/surface water interactions, topographic setting, and local meteorological conditions all contribute in determining stream thermal regimes.  This work discusses how these primary drivers of stream temperature can be incorporated into a physically based spatial model that can be applied for fisheries management at the watershed scale.