D E E P R A U R T LT MENT OF AGRICU United States Department of Agriculture Forest Service Pacific Northwest Research Station Assessing the Vulnerability General Technical Report PNW-GTR-884 of Watersheds to Climate July 2013 Change Results of National Forest Watershed Vulnerability Pilot Assessments The Forest Service of the U.S. Department of Agriculture is dedicated to the principle of multiple use management of the Nation’s forest resources for sustained yields of wood, water, forage, wildlife, and recreation. Through forestry research, cooperation with the States and private forest owners, and management of the national forests and national grasslands, it strives—as directed by Congress—to provide increasingly greater service to a growing Nation. 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To file a complaint alleging discrimination, write USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410, or call toll free, (866) 632-9992 (Voice). TDD users can contact USDA through local relay or the Federal relay at (800) 877- 8339 (TDD) or (866) 377-8642 (relay voice users). You may use USDA Program Discrimina- tion Complaint Forms AD-3027 or AD-3027s (Spanish) which can be found at: http://www. ascr.usda.gov/complaint_filing_cust.html or upon request from a local Forest Service office. USDA is an equal opportunity provider and employer. Authors* Contributors and Reviewers** Michael J. Furniss (retired), Pacific Northwest Christopher P. Carlson, Washington Office National Forest System Research Station Jim Morrison, Northern Regional Office Ken B. Roby (retired), Lassen National Forest Janine Rice, Rocky Mountain Research Station Dan Cenderelli, Stream Systems Technology Center Jeremy Littel, Climate Impacts Group, University of Washington John Chatel, Sawtooth National Forest Dan Isaak, Rocky Mountain Research Station Caty F. Clifton, Umatilla National Forest Charlie H. Luce, Rocky Mountain Research Station Alan Clingenpeel (retired), Ouachita National Forest Linda Joyce, Rocky Mountain Research Station Polly E. Hays, Rocky Mountain Regional Office David Cleaves, Washington Office Research and Development Dale Higgins, Chequamegon-Nicolet National Forest Sherry Hazelhurst, Washington Office National Forest System Ken Hodges, Chugach National Forest Sarah J. Hines, Rocky Mountain Research Station Carol Howe, Grand Mesa, Uncompahgre, and John Potyondy, Stream Systems Technology Center Gunnison National Forests Ryan Foote, Lassen National Forest Laura Jungst, Helena National Forest Ann Rosecrance, Ventura River Watershed Council Joan Louie, Gallatin National Forest Derik Olson, Council on Environmental Quality Christine Mai, Shasta-Trinity National Forest Ralph Martinez, Plumas National Forest ** All are USDA Forest Service, with units specified, Kerry Overton, Rocky Mountain Research Station except Jeremy Littel, Ann Rosecrance, and Derik Olson. Brian P. Staab, Pacific Northwest Region Rory Steinke, Coconino National Forest Mark Weinhold, White River National Forest * All are USDA Forest Service, with units specified. Cover Photograph North Pole Basin, Sopris Ranger District, White River National Forest, by Cindy Dean. Abstract Furniss, Michael J.; Roby, Ken B.; Cenderelli, Dan; Chatel, John; Clifton, Caty F.; Clingenpeel, Alan; Hays, Polly E.; Higgins, Dale; Hodges, Ken; Howe, Carol; Jungst, Laura; Louie, Joan; Mai, Christine; Martinez, Ralph; Overton, Kerry; Staab, Brian P.; Steinke, Rory; Weinhold, Mark. 2013. Assessing the vulnerability of watersheds to climate change: results of national forest watershed vulnerability pilot assessments. Gen. Tech. Rep. PNW-GTR-884. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 32 p. plus appendix. Existing models and predictions project serious changes to worldwide hydrologic processes as a result of global climate change. Projections indicate that significant change may threaten National Forest System watersheds that are an important source of water used to support people, economies, and ecosystems. Wildland managers are expected to anticipate and respond to these threats, adjusting management priorities and actions. Because watersheds differ greatly in: (1) the values they support, (2) their exposure to climatic changes, and (3) their sensitivity to climatic changes, understanding these differences will help inform the setting of priorities and selection of management approaches. Drawing distinctions in climate change vulnerability among watersheds on a national forest or grassland allows more efficient and effective allocation of resources and better land and watershed stewardship. Eleven national forests from throughout the United States, representing each of the nine Forest Service regions, conducted assessments of potential hydrologic change resulting from ongoing and expected climate warming. A pilot assessment approach was developed and implemented. Each national forest identified water resources important in that area, assessed climate change exposure and watershed sensitivity, and evaluated the relative vulnerabilities of watersheds to climate change. The assessments provided management recommendations to anticipate and respond to projected climate-hydrologic changes. Completed assessments differed in level of detail, but all assessments identified priority areas and management actions to maintain or improve watershed resilience in response to a changing climate. The pilot efforts also identified key principles important to conducting future vulnerability assessments. Keywords: Watersheds, hydrology, climate change, vulnerability, restoration, national forests. Contents 1 The Challenge 2 Watershed Condition, Health, and Resilience…What's the Difference? 3 The Pilot Assessment Approach 5 Identify Water Resource Values and Scales of Analysis 5 Water Resource Values 7 Scale(s) of Analysis and Reporting 8 Assess Exposure 8 Using Historical Data 8 Climate Change Projections 11 Evaluating Hydrologic Changes 11 Applying Exposure Projections 16 Evaluate Watershed Sensitivity 21 Evaluate and Categorize Vulnerability 25 Identify Adaptive Management Responses 28 Critique the Assessment 28 Data Gaps and Uncertainty 29 Other Lessons Learned 30 Summary 31 References 32 Appendix: Pilot National Forest Reports Pilot reports are available online only at http:/www.fs.fed.us/pnw/pubs/pnw-gtr884_appendix.pdf Assessing the Vulnerability of Watersheds to Climate Change The Challenge Water and its availability and quality will be the Clean and abundant water is often considered the main pressures on, and issues for, societies and the most valuable ecosystem service provided by the environment under climate change. national forests and grasslands, and most climate —Intergovernmental Panel on Climate Change changes affect hydrologic processes. Water from these lands is important for domestic, agricultural, Climate change poses important challenges to the U.S. and industrial uses, and for hydropower generation. Department of Agriculture Forest Service, the agency It supports recreational uses and provides crucial charged with management of more than 193 million acres of habitat for threatened, endangered, and sensitive public forests and grasslands. Current and projected trends aquatic species. in global warming present risks to a wide range of ecosys- tem values and services, and the impacts are most closely important differences is critical to setting priorities and associated with water resources, including changes in their identifying responses for management. volume, timing, and quality. Despite these challenges, Forest Service managers are In response, initial priorities of the Forest Service being directed to act. The agency’s climate change strategy climate change strategy are to build knowledge, skills, has been launched, and efforts to adapt to climate change and expertise, and to develop experience and partnerships. are now a reporting requirement for forest supervisors. A These initial steps build toward planning and designing Climate Change Scorecard measures progress made by each management actions to improve ecosystem resilience national forest and grassland in four areas, including assess- (Furniss et al. 2010). (In this report, “resilience” means ment of resource vulnerabilities. both the resistance to adverse changes and the ability of a Currently, there are few examples of assessments that watershed to recover following adverse changes.) inform managers about the vulnerability of watersheds to Maintaining or improving resilience is widely accepted climate change. Existing assessments are limited to analy- as the best means to adapt to climate change (Williams et al. ses of vulnerability of particular species or