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EPA Region 10 Climate Change and TMDL Pilot – South Fork Nooksack River, Washington Final Report
Klein, S., H. Herron, AND J. Butcher. EPA Region 10 Climate Change and TMDL Pilot – South Fork Nooksack River, Washington Final Report. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-17/281, 2017.
Region 10 of the U.S. Environmental Protection Agency (EPA) and EPA’s Office of Water and Office of Research and Development launched a pilot research project to explore how projected climate change impacts could be considered in the implementation of a Clean Water Act (CWA) 303(d) temperature total maximum daily load and how they might influence restoration actions in an Endangered Species Act (ESA) salmonid recovery plan. The pilot research project used a temperature TMDL developed by the Washington State Department of Ecology for the South Fork Nooksack River (South Fork) as the pilot TMDL for climate change vulnerability analysis. An overarching objective of the pilot research project was to support the goals and priorities of EPA’s climate adaptation plans. A range of projected climate change impacts from the Intergovernmental Panel on Climate Change emissions scenarios was evaluated as a risk assessment to thoroughly consider plausible futures of potential impacts to salmonids. The project consists of two separate research assessments: The qualitative assessment is a comprehensive analysis of freshwater habitat for ESA salmon restoration in the South Fork under climate change (EPA 2016). The objective of the qualitative assessment was to identify and prioritize climate change adaptation strategies or recovery actions for the South Fork that explicitly include climate change as a risk. The quantitative assessment provides a comparison of QUAL2Kw-modeled stream temperatures, including riparian shading, with and without climate change for the 2020s, 2040s, and 2080s (Butcher et al. 2016). A range of projected climate change impacts from a high-, medium-, and low-impact scenario was analyzed for each time period. This assessment discusses and considers the relevant CWA water quality standards developed to protect beneficial uses, including cold-water fisheries. Together, these two assessments identify comprehensive actions to protect CWA beneficial uses (salmon habitat) and ESA recovery goals under potential climate change. This final report provides an overarching summary of the pilot research project, including the methods used in and the findings of the quantitative and qualitative assessments. Stakeholder outreach and tribal engagement was considered a critical element of the pilot research project. Workshops, webinars, and working interdisciplinary teams have been used throughout the life of this project. The result is actionable science that, with the participation of scientists, environmental practitioners, and decision makers, supports the coproduction of knowledge for climate change adaptation. This Internal report contributes to ACE CIVA-2.7
This final report provides an overarching summary of the pilot research project, including the methods used in and the findings of the quantitative and qualitative assessments. It is written to appeal to a wide audience of policy makers, managers, agency staff and the general public. The South Fork Nooksack River (South Fork) is located in northwest Washington State and is home to nine species of Pacific salmon, including Nooksack early Chinook (aka, spring Chinook salmon), an iconic species for the Nooksack Indian Tribe. The quantity of salmon in the South Fork, especially spring Chinook salmon, has dramatically declined from historic levels, due primarily to habitat degradation from the legacy impacts of various land uses such as commercial forestry, agriculture, flood control, and transportation infrastructure. The Total Maximum Daily Load (TMDL) program, established by the Clean Water Act, is used to establish limits on loading of pollutants from point and nonpoint sources necessary to achieve water quality standards. The pollutant in this case is thermal load and allocations to reduce the load often involve restoration of stream shading, which reduces the solar input. While many temperature TMDLs have been established, the supporting analyses have generally assumed a stationary climate under which historical data on flow and air temperature can serve as an adequate guide to future conditions. Projected changes in climate over the 21st century contradict this assumption. We reran the QUAL2Kw model for future climate conditions (multiple climate models for the 2020s, 2040s, and 2080s) using gridded downscaled climate data and hydrologic model runoff predictions developed by the Climate Impacts Group at the University of Washington to modify the critical conditions inputs using a change factor approach. Establishing a mature riparian forest canopy can take 100 years, so it is important to begin planting riparian buffers now to reduce the anticipated climate change impacts on water temperature. High water temperatures in the South Fork are detrimental to fish and other native species that depend on cool, clean, well-oxygenated water. Of the nine salmon species, three have been listed as threatened under the federal Endangered Species Act (ESA) and are of high priority to restoration efforts in the South Fork—spring Chinook salmon, summer steelhead trout, and bull trout. This qualitative assessment is a comprehensive analysis of climate change impacts on freshwater habitat and Pacific salmon in the South Fork. It also evaluates the effectiveness of restoration tools that address Pacific salmon recovery. The objective of the assessment is to identify and prioritize climate change adaptation strategies or recovery actions for the South Fork that explicitly include climate change as a risk. The Beechie method (Beechie et al. 2013), with some adaptation to the South Fork watershed, was used to provide a systematic, stepwise approach to analyzing climate change impacts in the South Fork, including evaluation by climate risk (focusing on temperature, hydrologic, and sediment regimes), per salmonid species (emphasizing ESA-listed species), and per restoration action. We found that the most important actions to implement to ameliorate the impacts of climate change in the South Fork watershed are riparian restoration, floodplain reconnection, wetland restoration, and placement of log jams. Most of these actions are already being implemented to varying degrees, but the pace and scale of implementation will need to be increased by explicitly addressing barriers to implementation. This will require substantial planning including a watershed conservation plan, project feasibility assessments, agency consultation, landowner cooperation, stakeholder involvement, and funding.