Thermal Refugia Restoraion and Observation in the Klamath River

Project Objective: Conduct small scale restoration activities at selected creek mouths to enhance the physical parameters of associated thermal refugia and continue the long-term monitoring of salmonids at cold water refugia areas in the mainstem Klamath River using snorkel observations.





Project Description: Elevated water temperatures in river systems and the associated thermal stress on aquatic biota is an increasingly serious and widespread problem, especially in light of climate change. A primary line of questioning focuses on the role of thermal refugia to sustain salmonid populations. Thermal refugia can increase the carrying capacity of juveniles in thermally compromised streams and can allow the presence of salmonids in otherwise inhospitable habitats.





Within the Klamath River, thermal refugia are formed almost exclusively by cool water inflows from tributaries, with the lower reaches of these tributaries also providing thermal refuge habitat for juveniles and adults. These thermal refugia receive significant use by adult and juvenile salmonids (e.g. Chinook salmon, coho, and steelhead) during the warm summer months when the mainstem Klamath River regularly exceeds daily maxima of 24ºC; thereby exceeding the thermal tolerances of juvenile and adult salmonids. The elevated thermal regime, altered hydrograph, artificially restricted connectivity, and degraded water quality conditions of the mainstem Klamath River generally preclude uninterrupted summer rearing of juvenile salmonids in the absence of thermal refuges. For this reason, understanding, monitoring, protecting, and enhancing thermal refuges and their contributing watersheds within the mainstem Klamath River is important within the context of maintaining and restoring anadromous fish runs within the Klamath River watershed, especially in light of ongoing climate change.





During this proposed project, we will conduct small scale restoration activities at selected tributary mouths aimed at enhancing the habitat within the associated thermal refugia. The size of these enhancements depends on the size of the tributary and its existing thermal refugia, however somewhere between 400 and 2000 square feet encompasses the size of most planned improvement areas. We will use hand construction methods to improve fish passage into tributaries, and to install simple cover elements to thermal refugial areas. We will consolidate



braided flow channels into a single coherent stream channel at Pecwan, Tully, Ke’pel Creeks and other creeks, and will introduce simple cover elements at several of these sites as appropriate. The SONCC recovery plan highlights the importance of thermal refugia to juvenile and adult coho salmon in the Lower Klamath River (volume II, page 18-14).





A secondary goal of the project would be to continue the snorkel observation monitoring that has been conducted for the past 15 years, monitoring that has demonstrated the importance of thermal refuges to both holding and rearing salmonids.





In addition to juvenile salmonids, adult salmonids also make use of thermal refuges during times of elevated river temperatures. Snorkel observations will also enumerate any adult fish that may be using this habitat feature. During past years the YTFP has documented many thousands of adult salmonids using the Blue Creek thermal refuge. This area is also known to be a critical location in observed outbreaks of the fish disease Ich (Ichthyophthirius multifiliis) and our snorkel observations can act as an early warning system for potential disease outbreaks. This is one of the most important aspects of this project.

Project Benefit: This project will benefit Klamath River salmonids by enhancing critical thermal refugia habitat and allowing more salmonids to escape the elevated and lethal temperatures of the Klamath River. Additional benefits of the project include a census of salmonids using thermal refuge on the Lower Klamath River and the ability to provide real time data regarding salmonid congregations at thermal refugia to river managers.