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Identifying, protecting and restoring fine-scale thermal heterogeneity in Oregon coastal streams
Citation:
Ebersole, Joe. Identifying, protecting and restoring fine-scale thermal heterogeneity in Oregon coastal streams. MidCoast Watershed Council, Newport, OR, November 06, 2014.
Impact/Purpose:
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. Examples in the mid-coast of Oregon may include the lower Alsea and Yaquina rivers during summer low-flow conditions. 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, we provide considerations for a resilient and adaptive approach for management of thermal heterogeneity in streams and rivers, with special consideration of Oregon central coastal watersheds. 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.
Description:
The functional role of thermal heterogeneity to fish in warm streams has been well recognized in the scientific literature, and is increasingly invoked as an important aspect of biodiversity conservation. Water temperature standards designed to protect cold-water taxa are also beginning to incorporate concepts of thermal heterogeneity. Given this emphasis, there is a need to identify factors that create and maintain cold-water refuges in streams, and understand their functional significance to fish and other taxa. Stream structures and processes that influence hydrologic connectivity between subsurface and surface waters subsequently regulate thermal heterogeneity in streams. We will discuss implications of these processes for identification, monitoring, protection, and conservation of thermal heterogeneity with special consideration of mid-coast Oregon watersheds. Considerations for guiding a resilient and adaptive approach for management of thermal heterogeneity in streams and rivers 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.