Presenter/s: Andy Johnsen
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: riparian and water quality
ABSTRACT
The Kalispel Tribe of Indians and the U.S. Geological Survey are monitoring two cold-water refuge restoration sites at tributary confluences in an impounded portion of the Pend Oreille River, Washington for five years. The objective is to quantify changes in area and volume of cold water less than 18°C resulting from the placement of instream structures and modification of channel morphology at tributary confluence sites. We deployed high-resolution arrays of temperature loggers in a grid pattern at the restoration sites, conducted weekly flights with a drone equipped with a digital camera and thermal infrared imager, and mapped changes in water depth in the restoration sites. Variable flows from hydropower operations influenced the spatial and temporal dynamics of water temperature in an around the restoration sites. Thermal stratification was strongly associated with higher reservoir flows both before and after the restoration project was initiated. Cold-water patch surface area at locations greater than 50 cm deep increased compared to pre-restoration conditions but was highly variable. These preliminary findings suggest that year-to-year variability in summer reservoir flow may affect the spatial and temporal dynamics of cold-water refuges after restoration.