River Temperature Dynamics and Corresponding Surface / Streambed Heat Fluxes

English Abstract:

The thermal regime of rivers plays an important role in the overall health of aquatic ecosystems. River water temperature is important for water quality parameters that are considered when conducting environmental impact assessments and developing effective fisheries management. As such, it is important to understand the thermal behaviour of rivers and related heat exchange processes. This study looks at different heat exchange processes responsible for water temperature variability on both temporal (e.g., diel, daily, seasonal) and spatial scales (small vs. large rivers). Both surface and streambed heat fluxes were quantified within the studied watercourses. Surface heat flux was quantified using data from instream microclimate stations whereas streambed heat flux was quantified using measured temperatures within the streambed. Accordingly, streambed temperatures were measured at different depths and were used as a tracer to predict the magnitude and direction of groundwater flow using an inverse solution to the advection-conduction heat transport equation. The streambed flux analysis was carried out under different conditions, namely under natural surface water temperature conditions (i.e., as measured in the field), under steady-state conditions (e.g. under stream ice cover) and for conditions where the surface water temperatures followed a sinusoidal function. Modeling examples will be presented, including the implication of using water temperature models as a tool to better understand and protect important fisheries resources under current climate as well as under future climate conditions.