Presenter/s: Eric Berntsen
Symposium Session: 2024 - 08 Towards Effective Enhancement and Management of Cold-Water Refuges for Threatened and Endangered Aquatic Species: Global Practices and Regional Case Studies
Topics covered: modeling and water quality
ABSTRACT
Dam operations can affect mixing of the water column, thereby influencing cold-water refuge persistence and spacing. We examined associations between streamflow and water temperature among cold-water refuges in two dam-influenced rivers in inland northwestern USA in the summer months. To describe thermal and hydrologic patterns, we used in-situ thermographs and flow data from USGS gages. To determine whether tributary confluences could potentially be used as cold-water refuges by adult salmonids, we defined thermal refuges when bottom water temperatures in the confluences were at least two degrees cooler than the mainstem. We analyzed associations between streamflow, percent number of days when thermal refuges were stratified, and distance between cold-water refuges at different flows. We then developed flow thresholds for informing thermal refuge enhancement and management. Preliminary findings suggest that this approach can help identify the extent to which surface-release flows influence the persistence, spacing, and magnitude of cold-water refuges in rivers.