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Cold-water refuges for climate resilience in Oregon coastal stream
Citation:
Ebersole, Joe, C. Torgersen, AND D. Keenan. Cold-water refuges for climate resilience in Oregon coastal stream. Mid-Coast Technical Advisory Comjmittee, Newport, OR, April 13, 2016.
Impact/Purpose:
Many rivers and streams in the Pacific Northwest are currently listed as impaired under the Clean Water Act as a result of high summer water temperatures. Adverse effects of warm waters include impacts to salmon and steelhead populations that may already be stressed by habitat alteration, disease, predation, and fishing pressures. Much effort is being expended to improve conditions for salmon and steelhead, with increasing emphasis on enhancing watershed resiliency to prepare for future climate change. One climate change adaptation strategy that is gaining increased attention is the potential for thermal refuges to help mitigate the effects of increasing temperatures. EPA is conducting research to characterize thermal refuges for cold-water fish like salmon, and identify options and approaches to incorporating these features into watershed assessments, management plans, and restoration strategies. We define thermal refuges as areas buffered from regional climate effects by groundwater, physical habitat heterogeneity, or other watershed attributes. We found that these features can be critical to coldwater fish at certain times when rivers would otherwise be too warm for survival, but that there may be trade-offs associated with refuge use that should be considered when evaluating refuge effectiveness. We conclude with examples of types of watershed restoration actions that might help foster cold-water refuge creation and maintenance. This work contributes to an FY 16 deliverable under ACE CIVA 2.8
Description:
Many rivers and streams in the Pacific Northwest are currently listed as impaired under the Clean Water Act as a result of high summer water temperatures. Adverse effects of warm waters include impacts to salmon and steelhead populations that may already be stressed by habitat alteration, disease, predation, and fishing pressures. Thermal refuges may help mitigate the effects of increasing temperatures. In this presentation, we define cold-water refuges as areas buffered from regional climate effects by groundwater, physical habitat heterogeneity, or other watershed attributes. Processes forming these features include groundwater-surface water interactions, and hyporheic exchange at a range of spatial and temporal scales. Patterns associated with these processes may provide useful indicators for mapping and predicting the locations and extent of these features. Fish may congregate at high densities within cold-water refuges during critical periods of thermal stress, but there may be trade-offs associated with refuge use including predation, disease risk, and reduced foraging opportunities. These factors all contribute to determining refuge effectiveness. Watershed management and restoration strategies could consider these features and their potential utility to cold-water fish, and we conclude with examples of types of watershed restoration actions that might help foster cold-water refuge creation and maintenance.M