Fluid temperatures: Modeling the thermal regime of a river network

Abstract

Water temperature drives the complex food web of a river network. Aquatic organisms hatch, feed, and reproduce in thermal niches within the tributaries and mainstem that comprise the river network. Changes in water temperature can synchronize or asynchronize the timing of their life stages throughout the year. The water temperature fluctuates over time and place, creating variability in the network’s thermal regime. Because of this variability, many important details in the thermal regime of a river network cannot be simply represented by an average temperature. New research by Ashley Steel, a quantitative ecologist and statistician with the Pacific Northwest Research Station, and her colleagues documented the variability of water temperature over time and place on the Snoqualmie River network in Washington. They found clear spatial patterns in temperature metrics, and these patterns shifted over time. They demonstrated that it is possible to model key facets of the thermal landscape that are tied to the places and times in which coho and steelhead salmon are at critical life stages. Their findings provide a basis for more precisely focused habitat restoration efforts. This fundamental information can be used to develop tools that help identify where to take action to mitigate the effects of warmer air temperatures and of changes in winter precipitation on salmon and other species of concern.

Citation

Mazza, Rhonda; Steel, Ashley. 2017. Fluid temperatures: Modeling the thermal regime of a river network. Science Findings 201. U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 5 p.