A primer on stream temperature processes

Stream temperature is one of the most critical factors controlling aquatic ecosystem health. Practitioners and researchers from a range of fields, including biology, ecology, hydrology, engineering, and watershed management, are concerned with how climate and environmental changes are impacting stream thermal regimes. This primer provides an introduction to the various energy and water exchange processes that underpin stream temperature patterns from small headwater streams to large river systems. An overview of the various energy exchanges is provided, including (1) advection associated with hydrologic processes, and energy exchanges at (2) the stream–atmosphere interface and (3) stream–bed interface. The interaction and spatiotemporal variability of these energy exchange processes are discussed using a water and energy balance framework. A sound physical understanding and appreciation of the complex controls governing stream thermal regimes will help inform effective management strategies to sustain healthy aquatic ecosystems in a changing world.