Space, Time, and Temperature in Streams: Towards a General Framework for Understanding and Prediction of Thermal Regimes

Thermal regimes of rivers and streams, here defined as the total amount of variation through space and time, strongly influence all aspects of lotic biology. Thermal regimes emerge from the interactions among climate forcing (e.g., temporal variation in solar inputs, atmospheric heat, and hydrology), landscape geomorphology (e.g., elevation, topographic slope, basin size), vegetative controls on shading, natural disturbance, and anthropogenic factors. Previous research has described how subsets of those elements cause temporal variation at individual sites, spatial patterns among sites, or variation attributable to space-time interactions (i.e., differential sensitivity) but attempts to address all sources of variation simultaneously are rare. Using stream temperature datasets at national, regional, and landscape scales, we describe the relative importance of spatial and temporal variance within each to provide a general framework for understanding and prediction. Within this framework, covariates can be used to represent different sources of variation and tailor applications for thermal mapping, climate change, natural disturbance or anthropogenic modifications.