Presenter/s: Jeremy Payne
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: instream structure (culvert/bridge/dam), modeling, and water quality
ABSTRACT
The Pend Oreille River is a large, impounded river with epilimnetic releases from Albeni Falls Dam (Mejia et al. 2020), resulting in water temperatures which exceed the upper tolerances of adult Bull Trout (Salvelinus confluentus) and Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi). The US Geological Survey examined thermal heterogeneity across space and time in the Pend Oreille River and identified potential cold-water refuges for adult salmonids that were consistently below their physiological threshold (18°C) during low-flow summer conditions. Two locations along the Pend Oreille River (Indian Creek and Duncan Springs) near Usk, WA were identified as good candidates for cold-water habitat restoration due to high potential for increasing thermal habitat area, quality, and diversity.
This presentation will describe the analyses, design and construction of the two projects. Geomorphic analyses of the project sites and adjacent reaches of the Pend Oreille River were performed to identify channel planform patterns and geomorphic features that could be incorporated into the design. Existing and proposed temperature models using TELEMAC-3D were developed to better understand how the proposed design features impacted thermoregulation at the project areas. The geomorphic analysis and numerical modeling were used to develop a wood-based restoration design that mimicked natural geomorphic features and included structures intended to provide both aquatic habitat and refugia for native species, as well as retain cold water inputs to the maximum extent possible. Furthermore, the location, orientation, and depth of the proposed wood structures were designed to maximize habitat creation and functionality at all life stages of the target trout species.
The project was successfully constructed in September 2022. On-site design modifications were performed during construction to adapt the proposed habitat structures to changing field conditions and to ensure that the framework for desired habitat and geomorphic processes and functions were achieved. A companion talk will describe post-construction monitoring of the project.