The potential for restoring thermal refugia for cold-water fishes
1. What is the potential for stream and floodplain restoration for cooling water temperatures and creating thermal refugia in rivers?
The Bird Track Springs and Catherine Creek (CC-44) habitat improvement projects are two of many salmonid habitat improvement projects in the Grande Ronde River basin constructed as a result of the 2008 Federal Columbia River Power System Biological Opinion (NOAA Fisheries, 2008). The Catherine Creek restoration site was first constructed in 2013 with additional phases constructed thereafter. The Bird Track Spring site will begin construction in August, 2018. Project objectives are to improve physical and ecological processes through the project areas to benefit all stages of Chinook, steelhead, and bull trout. Restoration measures within the mainstem channel and along constructed side channels within the floodplain target specific limiting factors for salmonid viability such as temperature and rearing habitat (Justice et al., 2016). For example, the Bird Track Springs project includes construction of approximately 5,000 linear feet of new main channel, construction of approximately 9,500 linear feet of side channels, and construction of scores of riffles and wood structures within the side channels. A re-vegetation plan will provide long-term shading to the side and main channels.
Impacts to the thermal regime of the river within the project site associated with enhanced groundwater-surface water exchange through the hyporheic zone should be observed within a year as short and long hyporheic flow paths develop. Long flow paths are associated with greater cooling and require greater lateral hydrologic connectivity between the channel and floodplain aquifer (Poole et al., 2008). Long-term benefits to the thermal regime of the project site are associated with riparian and wetland plant establishment and concomitant shading.
To answer this first research question, we will analyze existing hydrologic and temperature monitoring dat
Need and Benefit
Elevated stream temperatures are a direct physical effect of river corridor alterations, land-use practices, and climate
change with explicit consequences on aquatic habitat (Battin et al., 2007, Ruesch et al., 2012). The impacts of
channel alteration and removal of riparian vegetation on stream temperatures are well understood (Poole and
Berman, 2001; Torgersen et al., 1999). Increasing stream temperatures has limited habitat for cold-water fish species,
eliminating refugia in many of our river systems. Furthermore, the increase in wildfire frequency and intensity along
with climate variability amplifies surface water temperatures, intensifying the risk to these threatened species
(Schindler 1998) and limiting the potential for species recovery. Reclamation and other federal agencies have devoted
significant resources into rehabilitating our rivers. Much of this effort has focused on salmonid species in the Pacific
Northwest (PN) and Mid-Pacific (MP) Regions; however, elevated water temperatures threaten cold water fishes
throughout the country.
The effectiveness of stream restoration efforts on rehabilitating cold water refugia are not well documented (Hester
and Gooseff, 2010). This scoping proposal will lay the groundwork for studying the potential of channel and floodplain
restoration on mitigating thermal impacts for target species. This is necessary to evaluate and advance Reclamation's
investment in restoration efforts and ensure its compliance with species recovery program mandates. Furthermore,
developing a better understanding of what restoration techniques are effective at rehabilitating cold water refugia will
ensure taxpayer dollars are spent efficiently.
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