You are here:
Identifying, protecting, and restoring thermal heterogeneity in streams.
Citation:
Ebersole, Joe L. Identifying, protecting, and restoring thermal heterogeneity in streams. Invited Oral Presentation to Salish-Kootenai College, Virtual, OR, October 21, 2020.
Impact/Purpose:
Warming streams and rivers are creating challenges for cold water fish like salmon and trout, resulting in reduced health and fitness of fish populations and losses to valuable commercial and recreational fisheries. Despite warming water temperatures, salmon and trout are able to persist in some rivers and streams because they are able find, access, and utilize cold-water patches created by groundwater, cold tributaries, or other sources of colder water. These features were common in some rivers and streams but have been lost due to a variety of human impacts. Protecting and restoring colder waters that can provide important resilience to fish populations is now an important part of climate change adaptation and management. Options and approaches for doing so will be discussed in this presentation.
Description:
An important cornerstone of managing for stream and river water temperatures protective of salmonids is the understanding that the region’s streams and rivers were naturally thermally diverse. While waters historically may have exceeded the thermal requirements of coldwater fishes in some cases, these waters often supported robust populations of salmon and trout. This was possible due to waters that were thermally diverse, with rivers and streams providing sufficient cold water pockets, either spatially or temporally, such that salmon could survive and flourish in what were otherwise ‘warm’ waters. Loss of thermal complexity has likely contributed to the decline of salmonid populations, particularly in warmer streams and rivers. EPA Region 10 recognized the importance of cold water refuges and natural thermal diversity in its Guidance on Temperature Water Quality Criteria. States and Tribes are subsequently adopting the Temperature Guidance and beginning to implement it. In this presentation, I provide considerations for a resilient and adaptive approach for management of thermal heterogeneity in streams and rivers. This will likely include: integration of multiple perspectives including hydrology, geomorphology, and ecology; recognition of hierarchical structure and context for thermal patterns and ecological responses; and anticipation and responsiveness to climate change.