Assessing the Vulnerability 

of Watersheds to Climate 

Change

Results of National Forest Watershed Vulnerability 

Pilot Assessments

Pacific Northwest 

Research Station

General Technical 

Report 

PNW-GTR-884

July 2013

United States Department of Agriculture

Forest Service

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Authors*

Michael J. Furniss (retired), Pacific Northwest 

 Research Station

Ken B. Roby (retired), Lassen National Forest

Dan Cenderelli, Stream Systems Technology Center

John Chatel, Sawtooth National Forest

Caty F. Clifton, Umatilla National Forest

Alan Clingenpeel (retired), Ouachita National Forest

Polly E. Hays, Rocky Mountain Regional Office

Dale Higgins, Chequamegon-Nicolet National Forest 

Ken Hodges, Chugach National Forest

Carol Howe, Grand Mesa, Uncompahgre, and 

 Gunnison National Forests

Laura Jungst, Helena National Forest

Joan Louie, Gallatin National Forest

Christine Mai, Shasta-Trinity National Forest

Ralph Martinez, Plumas National Forest

Kerry Overton, Rocky Mountain Research Station

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.

Contributors and Reviewers**

Christopher P. Carlson, Washington Office National Forest System

Jim Morrison, Northern Regional Office

Janine Rice, Rocky Mountain Research Station

Jeremy Littel, Climate Impacts Group, University of Washington

Dan Isaak, Rocky Mountain Research Station

Charlie H. Luce, Rocky Mountain Research Station

Linda Joyce, Rocky Mountain Research Station

David Cleaves, Washington Office Research and Development

Sherry Hazelhurst, Washington Office National Forest System

Sarah J. Hines, Rocky Mountain Research Station

John Potyondy, Stream Systems Technology Center

Ryan Foote, Lassen National Forest

Ann Rosecrance, Ventura River Watershed Council

Derik Olson, Council on Environmental Quality

**All are USDA Forest Service, with units specified, 

 except Jeremy Littel, Ann Rosecrance, and Derik Olson. 
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
1

Assessing the Vulnerability of Watersheds to Climate Change

Clean and abundant water is often considered the 

most valuable ecosystem service provided by the 

national forests and grasslands, and most climate 

changes affect hydrologic processes. Water from 

these lands is important for domestic, agricultural, 

and industrial uses, and for hydropower generation. 

It supports recreational uses and provides crucial 

habitat for threatened, endangered, and sensitive 

aquatic species.

The Challenge

Water and its availability and quality will be the 

main pressures on, and issues for, societies and the 

environment under climate change.

—Intergovernmental Panel on Climate Change 

Climate change poses important challenges to the U.S. 

Department of Agriculture Forest Service, the agency 

charged with management of more than 193 million acres of 

public forests and grasslands. Current and projected trends 

in global warming present risks to a wide range of ecosystem values and services, and the impacts are most closely 

associated with water resources, including changes in their 

volume, timing, and quality.

In response, initial priorities of the Forest Service 

climate change strategy are to build knowledge, skills, 

and expertise, and to develop experience and partnerships. 

These initial steps build toward planning and designing 

management actions to improve ecosystem resilience 

(Furniss et al. 2010). (In this report, “resilience” means 

both the resistance to adverse changes and the ability of a 

watershed to recover following adverse changes.)

Maintaining or improving resilience is widely accepted 

as the best means to adapt to climate change (Williams et al. 

2007). Forest Service managers have extensive experience 

in implementing practices that improve watershed health 

and resilience, such as restoring connectivity to aquatic 

habitats, restoring degraded wetlands, and using prescribed 

burning to restore fire regimes. 

Although much is known about the hydrologic impacts 

of climate change and the means to improve watershed 

resilience, linkages to integrate this knowledge into existing 

programs and priorities are needed. The capacity of national 

forests and grasslands to implement effective management 

measures is constrained by available resources (budgets 

and staffing). Priorities that integrate the impacts of climate 

change are needed to effectively allocate resources and 

focus management activities. 

Climatic changes are not expressed uniformly across 

the landscape. Not all watersheds are equally vulnerable. 

Some support more water resource values, and some are 

inherently more sensitive to change. Identifying these 

important differences is critical to setting priorities and 

identifying responses for management. 

Despite these challenges, Forest Service managers are 

being directed to act. The agency’s climate change strategy 

has been launched, and efforts to adapt to climate change 

are now a reporting requirement for forest supervisors. A 

Climate Change Scorecard measures progress made by each 

national forest and grassland in four areas, including assessment of resource vulnerabilities. 

Currently, there are few examples of assessments that 

inform managers about the vulnerability of watersheds to 

climate change. Existing assessments are limited to analyses of vulnerability of particular species or habitats (e.g., 

Gardali 2012). Likewise, existing protocols for vulnerability assessments (e.g., Glick et al. 2011) focus primarily 

on single species or specific biological communities. Not 

widely available are informative examples of place-based 

assessments that provide relative ratings of vulnerability of 

watersheds to climate change. 

In response to this information gap, the Forest Service 

Stream Systems Technology Center funded the Watershed 

Vulnerability Assessment (WVA) pilot project to determine 

if watershed-focused climate change assessments could 

be prepared by national forest staff, using existing data 

sources. The goal of the pilot project was to provide land 

managers with assessments of the relative vulnerability 

of watersheds to climate change. The project involved 

substantial collaboration between National Forest System 

(NFS) and Forest Service Research and Development staff; 

the task group included representation from two research 

stations and each of the nine Forest Service regions.
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General Technical report pnw-gt r-884

Watershed condition is the state of the physical 

and biological characteristics and processes within 

a watershed that affect the soil and hydrologic 

functions supporting aquatic ecosystems.... When 

watersheds are functioning properly, they create 

and sustain functional terrestrial, riparian, aquatic, 

and wetland habitats that are capable of supporting 

diverse populations of native aquatic- and ripariandependent species. In general, the greater the 

departure from the natural pristine state, the more 

impaired the watershed condition is likely to be... . 

Watersheds that are functioning properly have five 

important characteristics (Williams et al. 1997):

1. They provide for high biotic integrity, 

which includes habitats that support adaptive animal and plant communities that 

reflect natural processes.

2. They are resilient and recover rapidly from 

natural and human disturbances.

3. They exhibit a high degree of connectivity 

longitudinally along the stream, laterally 

across the floodplain and valley bottom, 

and vertically between surface and subsurface flows.

4. They provide important ecosystem services, such as high quality water, the 

recharge of streams and aquifers, the 

maintenance of riparian communities, and 

the moderation of climate variability and 

change.

5. They maintain long-term soil productivity.

—From the USFS Watershed Condition 

Framework (USDA FS 2011b)

This report summarizes the pilot effort. Because each 

NFS unit has different levels of staffing and data availability, the results represent a diversity of approaches on 

how to conduct a vulnerability assessment. We provide an 

overview of core assessment components, and highlight 

similarities and differences of the 11 pilot assessments. We 

also share important concepts that emerged during completion of the assessments. These “Assessment Principles” 

could be applied in assessments in other national forests and 

grasslands, and are described in boxes located throughout 

the report.

Each individual pilot assessment is locally based and 

has relevance at local scales. We do not attempt to summarize all of the findings of these assessments. The assessments represent a broad range of conditions similar to those 

found on national forests and grasslands across the country, 

and provide examples of approaches for a wide variety of 

environmental contexts. Readers are encouraged to review 

the individual pilot reports for details on methods used and 

results produced. These reports are available online at 

http:/www.fs.fed.us/pnw/pubs/pnw_gtr884_appendix.pdf.

Watershed Condition, Health, and 

Resilience...What’s the Difference?

For the purposes of this report, two frequently used 

terms—watershed condition and health—are considered 

interchangeable. Resilience is the capacity of a system 

to absorb disturbance and reorganize while undergoing 

change and still retain the same functions, structure, 

identity, and feedbacks (Walker et al. 2004). Because the 

term “resilience” is used most frequently in the climate 

change literature, we have used this term throughout this 

project and report. Watershed resilience can be described as 

a subset or synthesis of “watershed health” or “watershed 

condition” (Furniss et al. 2010).

The Forest Service has recently published a methodology to assess watershed condition (defined in box below), 

and has conducted baseline assessments across the entire 

193-million-acre NFS (USDA FS 2011a). This national 

program was initiated concurrent with the pilot WVAs.

Principles of Vulnerability Assessment

Derived from WVA Pilot Forests

1. Use resource values to focus the analysis.

2. The HUC-6 (hydrologic unit code level 6) subwatershed is currently the best scale for analysis 

and reporting. 

3. Local climate data provides context.

4. Analyze exposure before sensitivity.

5. Don’t get lost in exposure data.

6. Keep the end product in mind. 
3

Assessing the Vulnerability of Watersheds to Climate Change

The Pilot Assessment Approach

The scientist is not a person who gives the right 

answers; he’s the one who asks the right questions.

 —Claude Levi-Strauss

The WVA pilot team was composed of watershed and 

aquatic specialists from each Forest Service region, 

stationed on 11 national forests (see fig. 1). The group was 

supported by a steering committee composed of representatives from two research stations and two regional offices. 

Pilot national forests were selected to provide a range of 

water resource issues and environmental factors, and each 

national forest brought different levels of staffing, expertise, 

and existing information to the project. A few pilot forests 

had taken initial steps to consider how climate change might 

affect management priorities, though most had not. The goal 

was to conduct pilot assessments with a range of analytical 

rigor, in different geographic settings and organizational 

structures, with varying subject-matter focus.

The pilot team and steering committee met to develop 

a methodology to guide the assessments. The initial step 

was to define the purpose of the assessments, which was to 

identify (for each unit) areas with the highest priority for 

implementing actions to maintain or improve watershed 

resilience. This approach is based on two assumptions. 

The first is that there is a strong correlation between the 

condition and resilience of watersheds, with watersheds in 

better condition displaying more resilience than comparable 

watersheds in poor condition. The second assumption is 

that climate change is one of many factors, both natural 

and anthropogenic, that affect hydrology and watershed 

condition. A conceptual model illustrating these factors 

and linkages is displayed in figure 2.

The objective of the pilot assessments stemmed from 

the need to prioritize where to concentrate management 

activities to improve or maintain resilience. Comparing 

analysis options against this objective helped national 

forest staff focus their efforts.

Figure 1—Location of national forests participating in the pilot Watershed Vulnerability Assessments (WVA). Coordination was provided 

by representatives from regional staffs in Regions 2 and 6, and the Pacific Northwest and Rocky Mountain Research Stations. A parallel 

WVA was conducted on the Shoshone National Forest (Rice et al. 2012) and coordinated with the core WVA group of 11 pilot forests.
4

General Technical report pnw-gt r-884

The process was intended to produce useful results with 

differing levels of data availability and resource investment. 

Given the variety of watershed types, water resource issues, 

experience, and data availability on the pilot forests, a flexible assessment method was needed. The team developed an 

analysis method that relied heavily on previous experience 

with watershed analysis (USDA FS 1995) and the basic 

model of vulnerability (fig. 2). The assessment steps are 

summarized below.

The pilot assessments benefited from having leaders 

identified at the outset of the project. Leaders coordinated 

the assessment on their units, and at times acted as a 

one-person analysis team. A defined project leader was 

important to making key decisions on what to include in 

the assessment, identifying available data, determining how 

to analyze the information, and making adjustments when 

necessary.

Each pilot forest took a slightly different approach, 

depending on the resources selected for analysis, the type 

and amount of data available, and the staff time that could 

be devoted to analysis. After the assessments were initiated, 

the pilot team met monthly via video conference to discuss 

progress and share ideas and approaches. These discussions 

led to changes in the stepwise process and to the methods 

used in individual assessments.

For the WVA, vulnerability was defined as the interaction of climatic exposure with values at risk and watershed 

sensitivity. In the framework model, management actions 

are intended to increase the resilience or buffering capacity of watersheds by modifying the effect of stressors that 

decrease resilience. Each of the primary components of the 

assessment: values, exposure, sensitivity, vulnerability, and 

application and lessons learned from applying the conceptual model, are further described in the following section.

Figure 2—Conceptual model for assessing vulnerability, showing linkages between exposure, resource values, and system condition 

(sensitivity). We found utility in separating three components of sensitivity. “Buffers” and “stressors” are human-induced, whereas 

intrinsic sensitivity is based on inherent characteristics independent of human influence.

Management

Adaptive

capacity

Stressors

Buffers

Composite

sensitivity

Intrinsic

sensitivity

Exposure

to climatic

changes

Values Vulnerability

Values × Exposure × Sensitivity = Vulnerability 

affected by depends on controls results in

tends to decrease

depends on

depends on

tends to

decrease

tends to

increase

tends to

increase

modifies

modifies

Steps in the Watershed 

Vulnerability Assessments 

1. Identify water resource values and scales 

of analysis.

2. Assess exposure.

3. Evaluate watershed sensitivity.

4. Evaluate and categorize vulnerability.

5. Identify adaptive management responses.

6. Critique the assessment.
5

Assessing the Vulnerability of Watersheds to Climate Change

Identify Water Resource Values and 

Scales of Analysis

Ecosystem management is most successful when 

it considers and connects all spatial and temporal 

scales. For collaborative analysis, a specific scale 

and unit of land must be chosen, but this does not 

imply that only the collaborative analysis scale 

matters: they all matter.

—The authors

Water Resource Values

Identifying the water resources to be included is vital to 

the overall assessment. Water resources are the prism 

through which all the other assessment steps are viewed 

and focused. For example, factors used to characterize 

sensitivity and exposure are selected because they have 

strong linkages or they most directly affect the selected 

water resources.

Each pilot forest considered including at least three designated water resource values in their assessments. These 

were aquatic species, water uses (diversions and improvements), and infrastructure. The rationale was that climate 

change would influence these resources in different ways, 

and that including them in the pilot analysis would broaden 

the range of analytical methods and approaches.

Given this objective, each pilot forest selected water 

resource values based on their importance and perceived 

susceptibility to climate changes. All pilot forests included 

aquatic species (or habitat for selected aquatic species) and 

infrastructure in their analyses. Eight of the 11 pilot forests 

included the vulnerability of water uses in their assessments. The water resource issues addressed by each pilot 

forest, and the reporting scale, are listed in table 1.

The species (and aquatic habitats) selected for analysis 

represent the range of aquatic habitats found on the pilot 

forests. Anadromous fishes were a focus on each national 

forest where they occurred. Other salmonids included in the 

analyses were red-band trout, bull trout, brook trout, and 

three species of cutthroat trout. Brook trout are of note: they 

were a resource of concern within their historical habitat 

on the Chequamegon-Nicolet National Forest (NF), and a 

stressor (invasive species) on several of the Western pilot 

forests. Other fishes included as resource issues were warm 

Assessment Principle One

Use resource values to focus the analysis

One of the major challenges in conducting a broadscale analysis is deciding what to address. The land 

areas under consideration are large and ecosystems 

and social systems are extremely complex. Narrowing 

the focus of the pilot assessments was considered 

essential and was achieved by identifying key water 

resource issues using iterative analyses. 

One aspect of the approach instrumental in focussing 

the pilot efforts was using water resource values, 

identified at the outset, to drive the assessment. Once 

resources of concern are identified, assessment 

questions are narrowed. The question then is not what 

exposure attributes to use, but what exposure attributes have the strongest effect on the resource value. 

Likewise, the question “What elements influence 

watershed sensitivity?” narrows to “What watershed 

sensitivity elements most strongly influence the water 

resource?”

Using a specific set of resource values as the prism 

through which exposure and sensitivity were evaluated 

also provided for comparison of responses between 

resource values. Often, analysts found commonality 

among resources and were able to combine resources 

and methods to streamline the assessment. 

water species on the Ouachita and Coconino NFs. Amphibian species and habitat were included in three analyses.

The evaluation of water resources resulted in maps and 

descriptions displaying the location and relative importance 

by subwatersheds for each resource or combination of 

resources. For example, the Shasta-Trinity NF analyzed the 

density of springs and small lakes at three watershed scales 

(fig. 3). The Sawtooth NF displayed the relative importance 

of infrastructure (road crossings and near-stream recreation 

facilities) by subwatershed in the Sawtooth National Recreation Area (fig. 4). The characterization of watersheds in 

terms of the resources they support is an important step in 

any watershed planning effort and a first step in informing 

managers where limited resources might be invested. The 

assessment goal was to identify the most important places, 

categorize their relative value (high, moderate, low), and 

map the individual and composite values. 
6

General Technical report pnw-gt r-884

Figure 3—Density of springs and small lakes on the Shasta-Trinity National Forest. Results are shown at the scales of HUC-4 

(hydrologic unit code level 4) (left), HUC-5 (middle), and HUC-6 (right). The Shasta-Trinity assessment evaluated resource value, 

sensitivity, and vulnerability at the three scales, all showing that identifying priority locations for management actions was best 

done by using HUC-6. 

Table 1—Water resource issues, scope of analysis, and reporting scales included in pilot assessments

Region National forest Scale of analysis Reporting scale Water resource issues

1 Gallatin National forest HUC-6 (subwatershed) West-slope cutthroat trout, Yellowstone 

 cutthroat trout, water uses, infrastructure

1 Helena National forest HUC-6 (subwatershed) West-slope cutthroat trout, bull trout, 

recreational fisheries, infrastructure

2 Grand Mesa, Uncompahgre, National forest HUC-6 (subwatershed) Aquatic habitats and species, water uses, 

and Gunnison (GMUG) infrastructure

2 White River National forest HUC-6 (subwatershed) Boreal toad and cutthroat trout habitat, 

 water uses, infrastructure

3 Coconino Five HUC-5 HUC-6 (subwatershed) Amphibians, stream and riparian habitat, 

 watersheds water uses, infrastructure

4 Sawtooth Recreation area HUC-6 (subwatershed) Salmon, bull trout, water uses, infrastructure

5 Shasta-Trinity National forest HUC-6 (subwatershed) Springs, salmon, redband trout, water uses, 

 infrastructure

6 Umatilla National forest HUC-6 (subwatershed) Springs, salmon, bull trout, water uses, 

 infrastructure

8 Ouachita National forest HUC-6 (subwatershed) Warm-water fishes, infrastructure

9 Chequamegon-Nicolet National forest HUC-6 (subwatershed) Wetlands; cold-, cool-, and warm-water 

fishes; ground water; infrastructure

10 Chugach Eyak Lake and HUC-6 (subwatershed) Salmon, hydropower, infrastructure

 Resurrection 

 Creek watersheds 

HUC = hydrologic unit code.
7

Assessing the Vulnerability of Watersheds to Climate Change

Figure 4—Amount of infrastructure (roads and developed recreation facilities) within the 

Sawtooth National Recreation Area. Red-shaded subwatersheds have the highest density of 

infrastructure, yellow show moderate density, and green show the lowest density. Red lines 

are HUC-4 (hydrologic unit code level 4) boundaries.

Scale(s) of Analysis 

and Reporting

The pilot assessments were 

conducted over relatively large 

geographic areas, typically (8 of 

the 11 pilots) an entire national 

forest. Three forests analyzed 

smaller areas for specific reasons. 

The Chugach NF (Region 10) 

focused on subwatersheds where 

management activities would be 

most influenced by the results of 

the assessment. The Coconino 

NF (Region 3) included five 

watersheds (at the HUC-5 scale) 

that support the majority of aquatic 

resources on the forest. The Sawtooth NF limited its evaluation to 

the Sawtooth National Recreation 

Area because it supports remaining strongholds for steelhead, bull 

trout, and Chinook and sockeye 

salmon listed under the Endangered Species Act, and significant 

data were available for this area of 

the forest. 

All of the pilot forests used the 

subwatershed (HUC-6) scale for 

analysis and reporting. This arose 

from the shared conclusion that 

subwatersheds provide a logical 

unit and scale for setting priorities 

and implementing management 

activities on NFS lands.

The Shasta-Trinity NF also 

used the HUC-6 as the scale to 

apply results of the vulnerability 

assessment, and, in addition, evaluated water resource values, watershed sensitivity, and vulnerability 

at two broader scales (HUC-4 and 

Important Considerations in Assessing Water Resources

• Identify partners who can improve the assessment and engage with them.

• Identify the most important places (if possible), categorize their relative 

values (high, moderate, low), and map them. 

• Determine what relevant broad-scale evaluations, assessments, and 

plans are available.

• Consider all downstream uses (such as species and diversions).

• Identify any ecological thresholds or risk levels (flow requirements, 

temperatures, and so on) associated with specific resource values.

• As the assessment progresses, look for similarities (and differences) 

in response of resource values and consider grouping resource values 

where appropriate.
8

General Technical report pnw-gt r-884

HUC-5). The results from the Shasta-Trinity suggest that 

general trends can be expressed at broader scales, but as 

might be expected, detail shown at the HUC-6 scale is lost 

at each higher level (fig. 3). 

Although HUC-6 was determined to be the best 

reporting unit for displaying water resource values, 

sensitivity, and vulnerability, exposure information is 

generally available and appropriately used only at broader 

scales. As a result, most pilot forests evaluated exposure 

at the HUC-5 scale.

Assess Exposure

So why worry about global warming, which is just 

one more scale of climate change? The problem is 

that global warming is essentially off the scale of 

normal in two ways: the rate at which this climate 

change is taking place, and how different the “new” 

climate is compared to what came before.

—Anthony D. Barnosky

The consideration of climate change exposure data is the 

primary difference between the WVA and evaluations that 

Forest Service professionals have previously produced. Past 

assessments have been conducted for watershed analysis, 

restoration planning, and watershed condition. Pilot team 

members built upon this experience but few team members 

had used or were familiar with climate change projections. 

Analysis of exposure included four components: (1) 

review and evaluation of pertinent local historical climatic 

data, (2) selection and use of one or two modeled projections 

of future climate conditions, (3) analyses of historical and 

projected changes to hydrologic processes that might affect 

water resources, and (4) selection of metrics to analyze and 

display differences in exposure across each analysis area.

Using Historical Data

One finding consistent to all the pilots was the value of local 

historical data in providing local context and understanding of climate change. Display of historical changes with 

strong connection to local water resource values is typically 

easier to understand and appreciate than projections of 

future conditions. Projections are uncertain because they 

are associated with future emission scenarios and modeling 

assumptions. Differences between models increase because 

they are projected multiple decades into the future and 

display high variability that may be unsettling to managers. 

Historical data help both analysts and decisionmakers by 

providing local context and trends in climatic conditions. 

Two examples from the pilot assessments are included 

here. The first shows changes to ice cover on Lake Mendota 

in southern Wisconsin (fig. 5). This historical trend was 

obtained from the Wisconsin Initiative on Climate Change 

Impacts (WICCI) by the Chequamegon-Nicolet NF during 

the assessment process. The second example shows changes 

in snow depth from the Trinity and Sacramento River 

basins in the Shasta-Trinity NF (fig. 6). 

Climate Change Projections

Evaluation of climate exposure was the most difficult 

component of the assessment for several pilot forests, owing 

primarily to lack of experience with downscaled global 

climate modeling data. There were two basic challenges: 

deciding which climate change projections to use, and 

selecting the climate metrics.

Assessment Principle Two

The HUC-6 (hydrologic unit code level 6) is 

currently the best scale for analysis and reporting

The scale for the pilot assessments was not prescribed, but all pilot forests elected to use the HUC-6 

(subwatershed) scale to characterize and map results. 

Climatic exposure data was often available, displayed, 

and assessed at scales larger than HUC-6; the work 

by the Shasta-Trinity National Forest demonstrated 

that HUC-4 and HUC-5 scales are usually too large 

to effectively manage for water values, sensitivity, 

adaptive capacity, and resilience. The HUC-6 is the 

appropriate size for planning and implementing management strategies to sustain or improve watershed 

condition. In addition, HUC-6 is also the scale used 

to assess and report conditions for the Classification 

portion of the Watershed Condition Framework.
9

Assessing the Vulnerability of Watersheds to Climate Change

Figure 5—Duration of ice cover (days) on Lake Mendota in Wisconsin, 

1855–2009. Source: J. Magnuson, University of Wisconsin-Madison.

Figure 6—Changes in average snow depths from snow courses located in the Trinity River basin (1945–2009) and 

Sacramento River basin (1930–2009). 

The availability of downscaled climate model data 

has increased substantially since the WVA pilot project 

was initiated. Of particular note are data now available 

from the Climate Impacts Group (CIG) at the University 

of Washington. The CIG has evaluated available Global 

Circulation Models (GCMs), and determined which models 

and ensembles of models produce the best fit with historical 

data, for the major river basins of the Western United States. 

Data provided by CIG were used for evaluations conducted 

in Regions 1, 2, 3, 4, and 6. The Grand Mesa, Uncompahgre, 

Snow depth (inches) 

250

200

150

100

50

0

Klamath Province

Trinity Basin

West side of forest

(22 stations)

19451955196519751985199520052015

Snow depth (inches) 

250

200

150

100

50

0

Southern Cascades

Sacramento Basin

East side of forest

(19 stations)

1920193019401950196019701980199020002010

Maximum

Mean

Minimum

Assessment Principle Three

Local climate data provides 

context

Local or regional examples of historical 

changes in climate and to valued 

resources should be incorporated as 

components of the assessment. Such 

information (e.g., historical trends in 

temperature and precipitation, changes 

in ice duration, or species phenology) 

can readily illustrate current influences 

on water resources. These data are 

local, and usually of high confidence. 

Use of local and regional climatological 

data, field observations, and local 

knowledge helps to frame the importance of climate change in terms that 

are better understood and appreciated 

than relying only on model-based 

projections of future climate. 
10

General Technical report pnw-gt r-884

and Gunnison (GMUG) NFs used projections from CIG, 

and additional projections for the Upper Gunnison River 

(Barsugli and Mearns 2010). In retrospect, providing data 

available from CIG at the outset would have expedited some 

analyses and greatly assisted the process. 

In Region 2, the White River NF used projections supplied by the Colorado Water Conservation Boards (Ray et 

al. 2008, Spears et al. 2009). The Shasta-Trinity NF (Region 

5) used the World Climate Research Programme’s Coupled 

Model Intercomparison Project phase 3 (CMIP3) multimodel dataset. This is a downscaled global temperature 

modeling output available from the University of California, 

Santa Barbara. The Ouachita NF (Region 8) relied on information from The Nature Conservancy’s Climate Change 

Wizard (table 2). The Chequamegon-Nicolet NF (Region 9) 

employed data from WICCI, and the Chugach NF (Region 

10) used projections provided by the University of Alaska, 

Fairbanks Scenarios Network for Alaska Planning Project 

(fig. 7). 

All the pilot assessments used air temperature change 

projections in their analyses and most pilots included 

projected changes to precipitation. These projections were 

obtained from the variety of publically available state 

or regional climate sources listed above. All projections 

of future climate are based on GCMs. These models are 

Table 2—Modeled exposure data from the Ouachita National Forest assessment showing monthly and 

annual changes in temperature and precipitation derived from the B1 and A1B climate scenarios

Increases in temperature (°F) Percent change in precipitation

B1 2050 B1 2080 A1B 2050 A1B 2080 B1 2050 B1 2080 A1B 2050 A1B 2080

January 2.70 4.42 4.38 6.00 (0.69) 8.85 5.98 1.68

February 3.50 4.01 4.46 5.19 (0.97) (4.50) (2.54) (1.24)

March 3.46 4.25 4.70 5.74 (0.75) (4.30) 0.63 (5.17)

April 2.99 4.46 4.49 5.93 5.42 2.45 (1.19) 0.67

May 3.68 4.48 5.02 7.16 (8.46) (1.28) (6.26) (10.68)

June 3.90 4.64 5.34 7.04 (5.87) (7.17) (8.76) (12.37)

July 4.14 4.98 5.40 7.28 (8.34) (2.70) (7.39) (12.84)

August 4.13 5.04 5.21 6.84 1.20 6.97 1.52 2.61

September 4.23 5.49 5.35 7.45 (0.49) 1.10 (3.47) 1.32

October 4.12 5.46 5.29 7.15 (13.81) (8.17) (9.75) (8.17)

November 3.52 4.36 4.93 6.15 0.91 (5.08) (7.93) (8.75)

December 3.18 4.40 4.11 5.97 5.20 (9.39) (1.69) (1.68)

Annual 3.63 4.67 4.89 6.49 (2.22) (1.93) (3.40) (4.55)

Note: Decreases in precipitation are in parentheses.

Source: The Nature Conservancy Climate Change Wizard.

mathematical representations of atmospheric and oceanic 

motion, physics, and chemistry, and employ different 

emission scenarios to yield predictions of temperature 

and precipitation change. The global-scale model outputs 

are very coarse, so data are often downscaled and used as 

inputs to macro-scale hydrologic models for use in regional 

and finer scale analysis, such as the WVA pilots. The 

accuracy of the data becomes more uncertain with each 

subsequent layer of modeling. The greatest certainty is 

associated with air temperature projections. Precipitation 

projections are highly variable, with even less certainty 

for derived attributes like snowmelt, runoff, and stream 

baseflows. Precise changes in hydrologic extremes, such as 

flood and drought frequency, cannot be credibly modeled at 

the stream-reach scale at present.

The WVA pilot experience points to the value of 

broader scale (e.g., regional) vulnerability analyses in 

providing exposure data and recommending future climate 

scenarios to national forests. Interpreting exposure data 

at a broad scale would be useful for several reasons. First, 

exposure data are not available at finer scales. Second, 

consistency among national forests in selected emissions 

scenarios and modeling assumptions would allow comparisons of expected climate changes across national forests.
11

Assessing the Vulnerability of Watersheds to Climate Change

Figure 7—An example of a downscaled, gridded projection of future climate conditions. The maps display projected precipitation (mm). 

The projections are based on the A1B model. The figure is from the Chugach National Forest watershed vulnerability assessment.

2000–2009

Resurrection Creek

2020–2029

Resurrection Creek

2050–2059

Resurrection Creek

649–958

958–1,099

1,099–1,187

1,187–1,308

1,308–1,438

Mean 985.28

683–998

998–1,099

1,099–1,187

1,187–1,308

1,308–1,438

Mean 1,017.5

775–998

958–1,099

1,099–1,187

1,187–1,308

1,308–1,438

Mean 1,115.62

Evaluating Hydrologic Changes 

Using projections of future temperatures and other climatic 

changes, most pilot forests then considered what specific 

hydrologic changes would result from projected climate 

changes, and how water resource values would be affected 

by these changes. This step was integrative. In addition 

to the obvious connection between exposure and water 

resources, the evaluation served to stimulate thinking about 

which watershed characteristics might influence (either 

moderate or exacerbate) the hydrologic response to climate 

change, providing a segue to evaluating watershed sensitivity. An example of this type of analysis, which tracks 

climate changes through hydrologic responses to potential 

impacts on water resources from the Helena NF, is provided 

in table 3.

Applying Exposure Projections 

Once the hydrologic processes important to selected water 

resource values were established, exposure metrics closely 

linked to those processes were identified. The list of metrics 

used to characterize exposure was limited because of the 

commonality in water resources in the assessments (table 4). 

The selection of exposure metrics differed among national 

forests for three reasons. The first is the water resources 

themselves. The Chequamegon-Nicolet was the only pilot 

forest to include assessment of changes to ground-water 

recharge, and the only forest to use soil-water balance as 

an exposure metric. The second difference in selecting 

metrics was data availability. Both the Sawtooth and 

Umatilla assessments included finer scaled analysis of 

Assessment Principle Four

Analyze exposure before sensitivity

The first iteration of the watershed vulnerability 

assessment process used in the pilot project called 

for assessment of sensitivity before evaluating 

exposure. The result was development of rather 

generic sensitivity factors that did not have the 

strongest links to hydrologic processes most likely 

to be affected by climate. 

Exposure is considered first in order to produce a list 

of the most important hydrologic changes affecting 

each water resource. Sensitivity elements that strongly 

modify these hydrologic changes are then selected. 
12

General Technical report pnw-gt r-884

Table 4—National forests and metrics included to evaluate exposure effects in water vulnerability assessments

National forest Exposure metrics

Gallatin Combined flow, snowpack vulnerability

Helena Winter water temps, summer air temps, snow water equivalent (SWE), precipitation

Grand Mesa, Uncompahgre Seasonal temperature, aridity index 

and Gunnison (GMUG)

Ouachita Monthly precipitation and temperature

White River Snowpack vulnerability

Sawtooth Winter peak flows, summer stream temperature, summer flows

Coconino Snowpack vulnerability

Shasta-Trinity Air temperature, stream aspect, snowpack vulnerability 

Umatilla Winter and summer temperatures, SWE

Chequamegon-Nicolet Air temperature, precipitation, soil water balance, rainstorm frequency and intensity

Chugach Air temperature, precipitation, freeze and thaw days

Table 3—Projected hydrologic changes relative to identified values (Helena National Forest) 

Projected climatic changes Anticipated hydrologic response Potential consequences to watershed resources

Warmer air temperatures Warmer water temperature Decrease in coldwater aquatic habitats 

 in streams

Changes in precipitation Altered timing and volume of runoff Increases or decreases in availability of 

amounts and timing water supplies

 Altered erosion ratesComplex changes in water quality related to 

flow and sediment changes

Less snowfall, earlier Higher winter flows Changes in the amounts, quality, and distribution

snowmelt, increased of aquatic and riparian habitats and biota

snowpack density Lower summer flows

 Earlier and smaller peak

 flows in spring

Intensified storms, greater Greater likelihood of flooding Changes in aquatic and riparian habitats

extremes of precipitation 

and wind

Increased erosion rates and Increased damage to roads, campgrounds, 

 sediment yields and other facilities

Adapted from Furniss et al. 2010.

potential changes to water temperature in evaluating 

change to bull trout habitat. These analyses were possible 

because of the availability of stream temperature data and 

predictive models, and the support of the Rocky Mountain 

Research Station (RMRS). The third difference in exposure 

metrics was the level of analysis. Differences in the depth 

of analysis were partly the result of data availability, as in 

the example described above. But the amount of time team 

leads could devote to the assessment was also a factor. 

Available time and perceived need for detailed analysis 

were practical matters in the exposure analysis. Some 

pilots chose to make use of more detailed information that 

was available, and provided metrics with closer links to 

the subject water resources. Baseflow, for example, may 

be more closely linked with trout habitat than snowpack 

vulnerability, but the decision to conduct more detailed 

analysis was largely driven by the anticipated need for 

adequate detail to rate watersheds and set priorities. Some 

analysts thought that more detailed analysis would further 

discriminate areas at risk. Others thought the objective of 

rating watersheds could be met adequately with coarser 

evaluation of exposure. 
13

Assessing the Vulnerability of Watersheds to Climate Change

There are advantages and limitations to both the 

coarser and more detailed approaches to characterizing 

exposure. The common factor in cases where the most 

detailed analyses were conducted is that they evaluated 

effects on species which, because of population status and 

trend, were already the focal point of restoration strategies and management emphasis. In such cases, additional 

detail may be warranted. At the same time, exposure is the 

assessment component with the greatest level of uncertainty. Though there may be uncertainty in characterizing 

resource value, especially when ratings comprise more 

than one resource (e.g., frog plus fish species), descriptions 

of resource locations generally have little error. Likewise, 

assessments of sensitivity, as we will see in the next section, are composites of both intrinsic and anthropogenic 

factors. Schemes to combine or weigh the factors contain 

error, relative to how these factors are expressed in nature. 

Nevertheless, these assessment components are likely to be 

more accurate than projections of future temperature and 

snowpack, especially regarding what will actually occur 

decades from now. 

On the White River, Gallatin, and Coconino NFs, 

changes to snowmelt hydrology were determined to be the 

primary hydrologic change affecting selected resources. In 

both the White River and Coconino assessments, changes to 

the existing snow line resulting from projected temperature 

increases were anticipated. The watershed area within zones 

of predicted snow elevation change was used to characterize 

relative exposure of subwatersheds. The Gallatin NF assessment used projected changes in snowpack from the CIG 

(fig. 8). The Gallatin also included assessments of changes 

to summer and winter flow (from the variable infiltration 

capacity [VIC] model) in its assessment. A similar approach 

was taken on the Shasta-Trinity NF. 

The impact of climate change on stream temperatures 

and habitat for salmonids was the focus on four national 

Figure 8—Projected changes in snowpack vulnerability between historical and two future scenarios, Gallatin National Forest. Data are 

from the Climate Impacts Group (CIG) at the University of Washington, using the CIG composite model.

Historical 2040s 2080s

Snowpack vulnerability

Rainfall dominant

Transitional

Snowmelt dominant to transitional

Transitional to rainfall dominant

Gallatin National Forest

5th-level hydrologic unit code (HUC)

Snowfall dominant

Change from historical
14

General Technical report pnw-gt r-884

forests (Umatilla, Sawtooth, Helena, and Shasta-Trinity). 

These pilots employed data that looked deeper at potential 

hydrologic changes than other assessments. The Chequamegon-Nicolet NF included a salmonid (brook trout) in 

their assessment of potential impacts of stream temperature 

increases on 16 species of cold-, cool-, and warm-water 

fishes. In addition to stream temperature, the Sawtooth NF 

evaluated potential changes to frequency of flood flows 

critical to bull trout habitat condition. This evaluation was 

possible because of support from RMRS, a leader in assessing potential climate change impacts on aquatic ecosystems. 

The Ouachita NF selected aquatic communities as 

the resource of concern, and identified increased sediment 

production as the most likely adverse effect to that resource. 

Changes in precipitation and temperature from The Nature 

Conservancy’s Climate Wizard (see table 2) were captured 

by month from the composite climate change models. The 

predicted changes in climate were then used to modify 

the climate generator in the Watershed Erosion Prediction 

Project (WEPP) model (Elliot et al. 1995), which were 

then used to estimate sediment production under different 

climatic scenarios.

The Chequamegon-Nicolet NF’s assessment considered 

how climate change might affect important aquatic habitats, 

including lakes and wetlands. A soil water balance model 

was used to assess how potential ground-water recharge 

might change in the future and whether any change will 

differ by soil type. A ground water flow model will 

eventually be used to determine changes in ground water 

levels and flow rates to lakes, streams, and wetlands.

The analysis on the GMUG NFs differed from other 

assessments, in that results were displayed at a large scale. 

Six large geographic areas, stratified by climatic regime 

and elevation, were used for graphical analysis. Projected 

changes to maximum and minimum air temperatures and an 

index of aridity were factors used to rate exposure in each 

of these geographical areas. This analysis technique was at 

least partially driven by the resolution of the downscaled 

exposure data, which is typically on a grid of 6 km2 (fig. 7). 

This fairly gross resolution results in as few as two or three 

data points for an HUC-6, making discrimination at this 

scale inappropriate. As a result, pilots typically used HUC-6 

for distinguishing differences in resource densities and 

sensitivity, overlaid with a larger scale rating of exposure.

Climate models typically provide predictions of temperature and precipitation. These data are then combined 

with characterizations of watershed characteristics and vegetation in modeling of other hydrologic variables. The CIG 

has also developed predictions of hydrologic change based 

on the VIC model (Gao et al., n.d.). The CIG was extremely 

helpful in releasing data for use during the pilot study, and 

in explaining its utility and limitations. Variable Infiltration Capacity is a distributed, largely physically based 

macro-scale model that balances water and energy fluxes 

at the land surface and takes into account soil moisture, 

infiltration, runoff, and baseflow processes within vegetation classes. It has been widely used in the Western United 

States to study past and potential future changes to water 

flow regimes (e.g., Hamlet et al. 2009), snowpacks (Hamlet 

et al. 2005), and droughts (Luo and Wood 2007). Several 

pilot forests (Helena, GMUG, Coconino, and Sawtooth) 

made use of the VIC model outputs to evaluate exposure; 

VIC attributes evaluated by pilots included runoff, baseflow, and snow water equivalent.

Several pilot forests employed projections of changes 

to flow characteristics. These were selected because of their 

important influence on habitat for species of concern. Flow 

Assessment Principle Five

Don't get lost in exposure data

Pilot forests used exposure data of different 

specificity and detail (e.g., in one case, only air 

temperature change; in another, predicted stream 

temperatures). The level of detail influenced the 

analysis, but the take-home message is that all 

levels of exposure projections produced useable 

vulnerability assessments. Detailed projections at 

management-relevant scales are not necessary to 

gauge relative vulnerability of watersheds. It is more 

productive to move forward with the analysis than to 

get lost in the details of refining exposure data.
15

Assessing the Vulnerability of Watersheds to Climate Change

metrics were also useful in describing relative exposure 

of water uses. In contrast, predictions of peak- and lowflow responses to climate change are limited and consist 

primarily of generalized predictions of higher peaks and 

more severe droughts with warming climate (Casola et 

al. 2005). Only the Sawtooth NF applied a tool useful 

in describing exposure relative to increased peak flows 

and infrastructure. This analysis used the VIC-generated 

“Winter 95” metric. Winter 95 represents the number of 

days during winter that are among the highest 5 percent 

of flows for the year. Winter was defined as Dec. 1–Feb. 

28. Changes in Winter 95 were determined by comparing 

the increase in the number of days with the highest 5 

percent of flows between current and predicted conditions (2040 and 2080). Subwatersheds with less than a 

0.5-day increase were considered low risk, those with 

0.5- to 2-day increases were considered moderate risk, 

and subwatersheds with increases greater than 2 days 

were considered high risk. Results of this analysis for 

2040 are depicted in figure 9. 

At first glance, the difference in metrics and the 

level of detail might suggest that pilot forests took very 

different paths in their characterization of exposure. In 

fact, all took very similar approaches. All used review 

of historical data to display the trend in local climatic 

conditions. All pilot forests also first looked at projected 

temperature and precipitation changes. Sometimes this 

information had been compiled for states, sometimes for 

river basins or larger geographical areas. The commonality is that the analysis was broad scale. Next, pilot forests 

considered what impacts the climatic changes would have 

on hydrologic processes, and then how the hydrologic 

changes would affect water resources. Differences in 

pilot outputs resulted from decisions made at this point, 

primarily influencing the level of detail used to characterize the hydrologic changes. Perhaps the most valuable 

lesson learned by pilot forests in assessing exposure was 

that you do not have to become a climate scientist to do a 

climate change vulnerability assessment.

Figure 9—Winter peak flow risk from the Sawtooth National Forest 

watershed vulnerability assessment; showing current data (top) and 

projected data for 2040 (bottom). Ratings for subwatersheds are 

highest risk (red), moderate risk (yellow), and lowest risk (green). 

Ratings were developed by assessing change to frequency of highest 

streamflows occurring during the winter. Red lines are hydrologic 

unit code level 4 (HUC-4) boundaries.
16

General Technical report pnw-gt r-884

Evaluate Watershed Sensitivity

Models are tools for thinkers, not crutches for 

the thoughtless. 

—Michael Soulé 

The goal of assessing sensitivity was to place areas (subwatersheds) into categories based on how they would 

respond to the expected climate-induced changes to 

hydrologic processes. The sensitivity of watersheds to any 

change is partially a function of parent geology, soils, typical climate, topography, and vegetation. Human influences 

also affect watershed resilience, depending on the extent 

and location of management-related activities. 

Table 5—Attributes most commonly used in 

assessing sensitivity by the pilot forests

Intrinsic Anthropogenic

Geology Road density

Soil types Road-stream proximity

Risk of mass wasting Road crossings

Ground water baseflow Range condition

Slope Water diverted

Aspect Vegetation condition

The Forest Service often evaluates watershed condition; watershed specialists routinely describe watershed 

condition in National Environmental Policy Act (NEPA) 

analyses, and many national forests have watershed or 

aquatic species restoration plans in place that weigh heavily 

on assessments of watershed condition. Several pilot forests 

were able to take advantage of existing watershed condition 

ratings and apply them to their WVA. This included use of 

the Blue Mountains Forest Plan Revision watershed condition (Umatilla NF) and “Matrix of Pathways and Indicators” 

determination of watershed condition factors in conjunction with Endangered Species Act compliance for several 

salmonid species (Helena, Gallatin, and Sawtooth NFs).

Sensitivity indicators were selected that most influenced the hydrologic process and water resource value in 

question. Some indicators tend to dampen effects (buffers) 

and others to amplify effects (stressors). For example, road 

density may amplify peak flow response and the potential 

for flood damage to vulnerable infrastructure near streams. 

In contrast, investment in road improvements such as 

disconnection of road surfaces from streams would tend to 

buffer effects.

Attributes selected by pilot forests to characterize 

sensitivity included both intrinsic factors and anthropogenic 

or management-related factors (table 5). In some cases, 

pilot forests termed the “natural” factors as sensitivity, 

and the anthropogenic factors as risks, combining the 

two types of indicators to derive a measure of sensitivity. 

Most pilots included both types of indicators (intrinsic 

and anthropogenic), although two pilots (ChequamegonNicolet and Ouachita NFs) employed only intrinsic factors, 

and the Coconino NF selected only factors that related to 

management activities. A sample output (relative erosion 

Important Considerations in

Evaluating Exposure

• Quantify trends in available, relevant, historical 

climate datasets. Local and regional data 

that display significant changes demonstrate 

the likelihood that changes will continue into 

the future. Observed changes and trends in 

ecosystem traits, such as ice duration, species 

phenology, and species composition, are of 

great value. 

• Use best available climate change projections. 

Focus on near-term timeframes.

• Identify the effects of a changing climate on 

watershed processes to inform iterations of 

exposure data acquisition and assessment.

• Identify hydrologic processes important to 

the identified resource value. 

• Determine how projected changes in hydrologic 

processes might affect each resource value.

• Quantify the relative magnitude of differences 

in effects, including spatial and temporal 

variability. 

• Include disturbance regimes in the analysis and 

quantify disturbance-related effects.

• Document critical data gaps, rationale, and 

assumptions for inferences, references for 

data sources, and confidence associated with

assessment outputs.
17

Assessing the Vulnerability of Watersheds to Climate Change

Figure 10—Erosion sensitivity rating from the Grand Mesa, Uncompahgre, and 

Gunnison National Forests watershed vulnerability assessment. This rating was 

derived from subwatershed characterizations of runoff potential, rainfall intensity, 

stream density, density of response channels, and mass wasting potential.

sensitivity of subwatersheds on the GMUG 

NFs) is shown in figure 10. Soil hydrologic 

groups used to classify watershed sensitivity 

on the Chequamegon-Nicolet NF are shown 

in figure 11. 

The Chugach NF assessment used 

many of the same sensitivity attributes as 

the other pilot forests, but the approach 

differed in that the analysis consisted of 

comparing two watersheds with significant 

management activity (primarily undeveloped watersheds or those in wilderness 

were not included). 

Ratings from National Watershed 

Condition Classification were used in the 

sensitivity evaluation by the Coconino 

and Gallatin NFs. The Coconino was 

completing the condition classification at 

the same time the WVA was underway, and 

staff realized the utility that data developed 

would have in both efforts. The Coconino 

used few intrinsic factors to characterize 

watershed sensitivity. Most were derived 

from the Watershed Condition Classification 

(fig. 12). The Gallatin NF characterization of 

sensitivity had two components: one included 

intrinsic watershed attributes, the other 

included levels of disturbance. The Watershed 

Condition Classification ratings of “functioning,” 

“functioning at risk,” and “nonfunctioning” were 

used to characterize disturbance. Because national 

forests and grasslands now have completed the 

Watershed Condition Classification, these data 

would be useful in conducting future WVAs.

Pilot forests that took advantage of existing condition ratings tended to apply them to all 

resource issues. Several pilots, however, identified different indicators for each resource value. 

Although many indicators are important influences 

on multiple water resources, some are not. For 

instance, the most important factors affecting peak 

Figure 11—Average annual difference in potential ground water recharge 

by hydrologic soil group (HSG) (2046–2065 minus 1971–1990). HSG 

was one of two sensitivity attributes applied to the ground water resource 

issue in the Chequamegon-Nicolet National Forest watershed vulnerability 

assessment. Ground water recharge difference (inches/year)

1.50

1.25

1.00

0.75

0.50

0.25

0

-0.25

Hydrologic soil group

A B C D Water

Grand Mesa

Uncompahgre

West Elk

Upper Taylor

Cochetopa

San Juans

Erosion sensitivity rankings

Low

Moderate

High

Forest boundary

Geographic areas
18

General Technical report pnw-gt r-884

flows and infrastructure may differ from those that most 

influence springs and other aquatic habitats. 

Pilot forests took several approaches to developing 

ratings of watershed sensitivity. In the simplest applications 

(Ouachita and Chequamegon-Nicolet NFs), sensitivity indicators (e.g., basin slope, peat land type) were used to place 

watersheds into different categories. Other pilot forests 

produced sensitivity ratings based on numerous indicators. When multiple indicators were used, pilots developed 

methods of weighting and rating the relative influence of 

the attributes. For example, when considering influences 

on stream habitat, the amount of water withdrawn from a 

subwatershed is likely more important than the condition of 

terrestrial vegetation, and would therefore be given greater 

weight in calculating a sensitivity score. One approach 

to weighting sensitivity indicators, from the White River 

NF assessment, is shown in table 6. In several cases, pilot 

forests distinguished intrinsic and anthropogenic factors, 

Figure 12—Watershed condition factors from the Forest Service Watershed Condition Classification. Aquatic-physical attributes are not included. Factors shown in blue are those used as sensitivity indicators in the Coconino National Forest watershed 

vulnerability assessment.

Table 6—Summary of attribute types affecting subwatershed resilience to climate change 

(White River National Forest)

Net effect relative 

Subwatershed attribute Type of attribute Relative weight to climate change

Geochemistry of parent geology Inherent to watershed 0.25 Buffer

Extent of glaciation Inherent to watershed 0.75 Buffer

Aspect Inherent to watershed 0.50 Additive

Hydroclimatic regime Inherent to watershed 1.0 Additive

Weighted precipitation Inherent to watershed 1.0 Buffer

Extent of surface water features Inherent to watershed 1.0 Buffer

Extent of large-scale pine beetle mortality Inherent to watershed 0.5 Buffer (short term)

Water uses Anthropogenic 1.0 Additive

Development (primarily roads) Anthropogenic 0.5 Additive

Extent of beetle salvage Anthropogenic 0.5 Additive (short term)

and used a categorical matrix approach to combining and 

categorizing sensitivity, into a single rating. An example 

of such an approach (from the GMUG NFs) is displayed in 

figure 13.

On the Sawtooth NF, assessment of watershed condition was aided by use of Bayesian belief networks (Lee and 

Rieman 1997). The networks were used to evaluate relative 

differences in predicted physical baseline outcomes. The 

basic structure employs a box-and-arrow diagram depicting 

hypothesized causes, effects, and ecological interactions 

(see fig. 14). The system was used to weight the relative 

importance of, and connections between, a comprehensive 

list of intrinsic and management attributes, and watershed 

and habitat elements. As with the other pilot assessments, 

results from this process were used to rate watershed condition as high, moderate, or low.

Although there was no detailed comparison of the 

products developed from these varied approaches, they 

Aquatic biological

● Life form presence

● Native species

● Exotic and/or invasive species

● (Riparian) vegetation condition

Terrestrial physical

● Density

● Road maintenance 

● Proximity to water

● Mass wasting

● Soil productivity

● Soil erosion

● Soil contamination

Terrestrial biological

● Fire condition class

● Wildfire effects

● Loss of forest cover 

● (Rangeland) vegetation condition

● (Riparian) invasive condition

● (Forest) insects and disease
19

Assessing the Vulnerability of Watersheds to Climate Change

Figure 14—Bayesian belief network for determining overall physical condition, from the 

Sawtooth National Forest watershed vulnerability assessment. Contributing factors included 

habitat access, flow, channel condition, habitat elements, water quality, and watershed 

conditions.

Figure 13—Scheme used to rate watershed sensitivity on 

the Grand Mesa, Uncompahgre, and Gunnison National 

Forests. The matrix combines ratings for watershed 

stressors and sensitivity. Ratings of erosion sensitivity 

(six elements) and runoff sensitivity (seven elements) were 

combined to produce the sensitivity rating. The stressor 

rating was derived by combining ratings of past management (two elements), roads (three elements), vegetation 

treatments, private land, and mining.

had one thing in common: they all made use of available 

information to the greatest degree possible. By using 

existing condition or sensitivity ratings or developing them 

from scratch, each pilot forest produced useful ratings of 

watershed vulnerability. It is very important to determine 

what intrinsic and management-related attributes are 

important influences on watershed condition, as they 

strongly affect the selected water resources. If available 

data, analyses, or assessments include attributes that match 

those identified in the WVA process or may serve as 

surrogates, it makes sense to use them.

Stressors

Sensitivity

Low Moderate

Low Low

Moderate Low

Low Low

High

High

High High High High

Low

Sensitivity × Stressors

Risk Ranking Matrix

The sensitivity evaluation typically resulted in maps 

showing relative sensitivities of subwatersheds. Two 

examples of this type of product are displayed. Figure 15 

shows the sensitivity rating from the Umatilla NF, where 

(like the GMUG example) a matrix was used to produce a 

combined rating of intrinsic and anthropogenic factors. A 

combined sensitivity rating was applied to a composite of 

resource values. The Coconino 

NF developed different sensitivity ratings for each water 

resource issue (fig. 16). 

Recent trends and projected 

future trends in resource conditions should also be included. 

For example, increased water 

diversion could exacerbate 

effects on a resource, whereas 

anticipated road improvements 

could improve condition and 

reduce effects that might otherwise occur.

Important Considerations in

Evaluating Sensitivity

• Determine the intrinsic factors (such as geology, 

soils, and topography) affecting the hydrologic 

processes of concern—those that can most 

affect the resource values. 

• Determine the management factors (such as 

roads and reservoirs) affecting the hydrologic 

processes of concern.

• Determine if management activities will serve as 

buffers or stressors.

• Consider weighing the relative importance of the 

buffers and stressors in influencing condition and 

response.

• Evaluate trends or expected trends in stressors, 

and how management actions and restoration 

could affect them. 
20

General Technical report pnw-gt r-884

Figure 15—Composite rating 

of watershed sensitivity from 

the Umatilla National Forest. 

Factors used in the rating 

include ground-water dependence, watershed restoration 

investment category, road density, near stream road length, 

road grade, range condition, 

forest vegetation condition, 

and aquatic habitat condition. 

White areas have no National 

Forest System ownership.

Figure 16—Watershed sensitivity for 

stream habitats, Coconino National 

Forest. Attributes contributing to this 

rating were derived from the forest’s 

watershed condition classification. 

Stressors included water diversions, 

terrestrial vegetation condition, 

riparian vegetation condition and 

invasive species, road proximity 

to streams, and wildfire. Buffers 

included holding instream water 

rights and degree of implementation 

of regional ground-water policy.

High

Moderate/high

Moderate

Moderate/low

Low

Subwatersheds

Umatilla National Forest

Sensitivity

Stream Habitat Sensitivity Rating

Coconino National Forest 

Watershed Vulnerability Assessment

High

Medium

Low
21

Assessing the Vulnerability of Watersheds to Climate Change

Evaluate and Categorize Vulnerability

Climate change is a risk-multiplier... any decline 

in the ecological resilience of one resource base or 

ecosystem increases the fragility of the whole.

—Charles, Prince of Wales, addressing 

United Nations climate conference COP15 

in Copenhagen (December 2009)

A relative rating of vulnerability of water resources to 

climate change was produced by combining information 

from the evaluation of resource values, exposure, and 

sensitivity. Pilot forests used a variety of approaches to 

complete this step. Primary determinants were the number 

of water resources selected for analysis, and the way that 

values, sensitivities, and responses had been described. 

Some pilot forests classified vulnerability based on a 

threshold or ecological value (such as the amount of wetland 

area in each watershed, as shown in the ChequamegonNicolet example in fig. 17). The most common approach 

used by pilot forests was to merge the location of values 

with ratings of watershed sensitivity, and then overlay that 

summary rating with differences in exposure. The result 

Figure 17—Classification of 

climate-change risk to wetlands 

on the Chequamegon-Nicolet 

National Forest. The rating is 

based on the proportion of total 

wetland and acid wetland within 

the national forest boundary 

in each HUC-6 subwatershed. 

Total wetland area ranged from 

0 to 55.8 percent of the area 

for all HUC-6 watersheds. 

The HUC-6s with less than 10 

percent were rated “low,” those 

with 10 to 30 percent were rated 

“moderate,” and those with 

greater than 30 percent were 

rated “high.” The HUC-6s with 

less than 5 percent acid wetland 

area were rated “low,” those 

with 5 to 15 percent were rated 

“moderate,” and those with 

greater than 15 percent were 

rated “high,” and above that 

value were “very high.” These 

two risk classes were combined 

to form one vulnerability classification for each watershed.

National

forest

boundary

HUC-6

Wisconsin

counties

Low

Moderate

High

Very high

Relative vulnerability of wetlands to 

climate change for HUC-6 watersheds on 

the Chequamegon-Nicolet National Forest 

of combining these elements is a classification, typically 

by subwatershed (HUC-6), that displays the relative 

vulnerability of the identified values. All pilot forests 

provided a narrative and mapped their results. Some pilots 

combined resource values in the analysis (see fig. 18), and 

others displayed resource values separately (figs. 17 and 

19). The GMUG NFs’ summary rating of vulnerability was 

presented in tabular format (table 7). The GMUG assessed 

exposure and rated vulnerability at the watershed scale. 

The GMUG’s adjusted vulnerability ranking combines the 

ratings of values, sensitivity, and exposure. 

Based on its strong partnership with RMRS and its 

access to considerable habitat condition data (including 

stream temperature data), the Sawtooth NF conducted the 

most detailed evaluation. The Sawtooth analysis included 

assessing the effects of potential changes to stream temperature and flow on bull trout. Potential temperature effects 

were analyzed by summarizing the available stream miles 

that were within or exceeded 15 °C within each bull trout 

patch for 2008, 2040, and 2080 timeframes. Impacts on 

both low flow and winter flows were also assessed. Change 
22

General Technical report pnw-gt r-884

in mean summer flow was evaluated by looking at the percentage of change in flow from current to 2040 and 2080. 

Changes of less than 20 percent of baseflow were considered low risk, 20 to 40 percent were considered moderate, 

and greater than 40 percent were considered high risk. Winter flow analysis compared how the number of days with the 

highest 5 percent flows increased from current to 2040 and 

2080. Subwatersheds with less than a 0.5-day increase from 

current conditions were considered at low risk, 0.5- to 2-day 

Figure 18—Vulnerability ratings from the Coconino National Forest. The map 

displays the subwatersheds with the highest density of water resource values 

(native fishes, amphibians, water uses, stream habitat, riparian and spring 

habitat, and infrastructure) that also have high or moderate sensitivity and 

high or moderate exposure.

High value, sensitivity and exposure

High value and sensitivity, moderate exposure

High value, moderate sensitivity and high exposure

Composite Aquatic Resource

Coconino National Forest 

Watershed Vulnerability Assessment

increase were considered at moderate risk, and greater than 

2-day increase from current conditions were considered at 

high risk. Once the individual elements were analyzed, a 

Bayesian Belief Network was used to rate the impact of the 

change on bull trout population persistence. The vulnerability rating resulting from this process (the extinction risk for 

bull trout) is shown in figure 20.

On the Ouachita NF, predicted changes to precipitation 

were applied to WEPP:Road modeling of road sediment 

production and compared to modeled 

estimates of existing condition. Changes 

in future conditions were then compared 

to existing correlations between aquatic 

assemblages and sediment production, 

which include high, moderate, and low 

risk categories. In this case, the assessment 

illustrates the differences in risk categories 

that exist presently, and those projected to 

result from climate change.

As with some other aspects of the 

WVA, the Chugach NF took a different 

approach to assessing vulnerability, owing 

to the fact that they analyzed only the two 

subwatersheds in their analysis area that 

are subject to management activities. Their 

objective was to look at those two subwatersheds and identify specific vulnerabilities 

and possible mitigations. The Chugach 

assessment focused on potential changes to 

salmonid habitat. The creeks and tributaries in the two subwatersheds are currently 

cold enough that the projected increase 

in water temperatures would not exceed 

optimal temperatures. The key concern was 

the unknown response of other organisms 

(including aquatic invertebrates). Of specific 

interest was whether increased water temperatures would alter the life cycles of prey 

species currently synchronous with newly 

emerged salmon fry.
23

Assessing the Vulnerability of Watersheds to Climate Change

Figure 19—Climate change vulnerability rating for the water uses resource value, White River National Forest. Red shading depicts 

subwatersheds with the highest vulnerability. Points of diversion for water uses are shown as black dots.

Table 7—Vulnerability ratings from the Grand Mesa, Uncompahgre, and Gunnison 

National Forestsa

Exposure Value risk ranking Vulnerability Adjusted 

Geographic areas ranking (weighted average) rankingbvulnerability rankingc

Uncompahgre 6 1 7/12 = 0.583

Grand Mesa 5 2 7/12 = 0.584

San Juans 4 6 10/12 = 0.836

West Elk 3 3 6/12 = 0.502

Upper Taylor 2 5 7/12 = 0.585

Cochetopa 1 4 5/12 = 0.411

a

 Exposure was ranked for the six landscape units (a composite of HUC-6 subwatersheds) on the forest (1 is the lowest), based 

on biggest change in annual average maximum temperature, annual average minimum temperature, and percentage of change in 

annual aridity index. Value risk ranking is the highest risk to values based on weighted average of acres × count of high rankings 

for each subwatershed.

b

 Exposure ranking + value risk ranking)/12.

c

 Upper Taylor adjusted > Grand Mesa and Uncompahgre (area in high risk); Grand Mesa adjusted > Uncompahgre (higher 

concentration of values).

Watershed Ranking 

Water Uses

Water diversions

● A—Active structure with no contemporary diversion records

● C—Conditional structure

● U—Active structures but diversion records are not maintained

Water uses ranking

High

Moderate

Low

Watersheds level 6

Administrative forest

0 5 10 20 Miles

o
24

General Technical report pnw-gt r-884

Figure 20—Predicted bull 

trout persistence in 2040 for 

subwatersheds in the Sawtooth 

National Recreation Area. Redshaded subwatersheds are at high 

extinction risk, yellow-shaded are 

at moderate risk, and green are at 

low risk (subwatersheds without 

bull trout are not colored). Red 

lines are HUC-4 boundaries. 

Pilot forest staff brought a variety of skills and backgrounds to their assessments. Some assessments were prepared by teams, some primarily by one person. In addition, 

there was great variation in the types and amount of available information. Despite these differences, each pilot forest 

was able to conduct an assessment and report the results in 

an effective way. There were many differences in how the 

individual steps were approached, and the results reflect 

these differences. All the vulnerability ratings were derived 

by combining values, sensitivity, and exposure. We believe 

that the performance of the pilots in completing meaningful 

assessments using the basic process should encourage other 

units desiring to conduct vulnerability assessments.

Important Considerations in

Evaluating Vulnerability

• Identify where the location of water resource 

values overlaps with highest sensitivity and 

greatest exposure. 

• Determine how changes in hydrologic processes 

affect water resource values.

• Determine the relative vulnerabilities of 

watersheds across the assessment area (e.g.: 

low, moderate, high) to inform priorities for 

adaptive response to predicted climate change. 
25

Assessing the Vulnerability of Watersheds to Climate Change

Identify Adaptive Management Responses

Nobody made a greater mistake than he who did 

nothing because he could only do a little. 

—Edmund Burke 

Each pilot forest produced an assessment that effectively 

displays the location of water resources of concern, key 

climate change metrics, and watershed sensitivities of the 

resources to the projected changes. The combination of 

these elements yielded relative ratings of watershed vulnerability to climate change. As such, the assessments met the 

objective of providing managers with information necessary 

to identify priority areas to undertake management actions. 

Management priorities should focus on maintaining or 

improving watershed resilience. Resilience is the capacity of 

an ecosystem to respond to a perturbation or disturbance by 

resisting damage and recovering quickly (Holling 1973). By 

definition, resilient watersheds are better able to continue 

delivery of ecosystem services when subjected to ecological 

change, including changes that might result from a warming 

climate. A related assumption is that watershed resilience 

is closely tied to watershed sensitivity. Watershed resilience 

is a product of both inherent sensitivity and anthropogenic 

influences on watershed condition.

The results of the WVAs will be useful in development of management options and strategies. This includes 

discussion of which vulnerability classes should be highest 

priority for management actions. If, for instance, a highly 

valued water resource has a very limited distribution, 

management options are limited. If the value is more widely 

dispersed, managers must decide if the most vulnerable 

areas should be highest priority, or if they should focus 

their efforts on sustaining the values in areas with lower 

vulnerability. Scale must be considered in this discussion. 

Naturally, for resources (especially species) whose range 

is greater than the analysis area, discussion of results with 

other land managers will be necessary.

The greatest value of WVA results is in identifying 

geographical areas that are priorities for actions designed 

to maintain or improve watershed resilience. Several pilot 

forests are already using the results to this end. The recently 

completed Watershed Condition Classification (fig. 21) led 

to the designation of priority subwatersheds for improvement actions. The connection of the WVA to setting these 

priorities is clear. One pilot forest (Coconino NF) applied 

WVA findings during this priority-setting process. On 

many national forests and grasslands, strategic plans have 

been developed to guide restoration and management 

efforts. In these cases, the vulnerability assessment process 

will be used to reassess existing priorities and to determine 

if changes are warranted. None of the pilot forests was 

engaged in land management planning during the WVA, 

but results have clear application to that effort in helping to 

identify priority areas for management. 

One pilot forest (Ouachita NF) incorporated potential 

management actions in its sensitivity ratings. A tabular 

result from the Ouachita (table 8) displays the number of 

subwatersheds in different watershed risk classes. These 

ratings were derived from estimates of current and future 

sediment production. In this assessment, future changes to 

Assessment Principle Six

Keep the end product in mind

A plethora of climate change exposure data are 

now available. Models are continually refined. The 

number, types, and detail of climate projections 

can be confusing and overwhelming. Managers 

and analysts should realize that projections have 

substantial uncertainty and that uncertainty grows 

with down-scaling and time. 

Most pilot forests structured their analyses such 

that actual values for temperature changes, runoff 

changes, etc., were not critical. The focus was, 

instead, on the ranges and direction of projected 

changes. 

This approach was appropriate, because the 

objective was to produce a relative vulnerability 

rating to inform decisions about priority areas for 

management. 

Periodically reflecting on the goal—what decisions 

need to be informed—helps put the need for data 

and precision in perspective. The necessary depth 

of analysis is that which will produce these relative 

ratings.
26

General Technical report pnw-gt r-884

Figure 21—U.S. Department of Agriculture Forest Service Watershed Condition Framework. 

Watershed vulnerability assessments contribute directly to steps 1, 2, and 3.

Table 8—Vulnerability ratings (by risk class) of subwatersheds on the Ouachita National 

Forest, as influenced by climate change scenarios and application of road management 

actions (maintenance to standard and closure of user-created trails)

Climate change scenarios

2010 2050 B1 2080 B1 

2010 with road with road with road 

Risk current management 2050 B1 management 2080 B1 management

High 88 82 93 85 93 85

Moderate 46 40 42 43 42 43

Low 56 68 55 62 55 62

2050 A1B 2080 A1B 

with road with road

2050 A1B management 2080 A1B management

High 105 96 105 96

Moderate 44 43 45 43

Low 41 51 40 51

STEP 1

Classify Watershed

Condition

STEP 2

Prioritize Watersheds

for Restoration

STEP 3

Develop Watershed

Action Plans

STEP 4

Implement Integrated

Projects

STEP 5

Track Restoration

Accomplishments

STEP 6

Monitor and

Verification
27

Assessing the Vulnerability of Watersheds to Climate Change

precipitation were predicted to increase sediment production, with subsequent impacts on aquatic communities. 

Shown are the projected change in watershed condition 

class caused by climate changes from conditions in 2010 to 

those projected for 2050 and 2080, and potential modifications to the response from road management activities. 

The analysis demonstrates that implementation of road 

management activities could reduce the number of subwatersheds with high risk ratings. In terms of setting priorities 

for management, subwatersheds where implementation of 

road improvements would reduce vulnerability should be 

considered for high priority.

Road improvements were identified as a key action to 

improve condition and resilience of watersheds on all the 

pilot forests. In addition to treatments that reduce erosion, 

road improvements can reduce the delivery of runoff from 

road segments to channels, prevent diversion of flow during 

large events, and restore aquatic habitat connectivity by 

providing for passage of aquatic organisms.

As stated previously, watershed sensitivity is determined by both inherent and management-related factors. 

Managers have no control over the inherent factors, so to 

improve resilience, efforts must be directed at anthropogenic influences such as instream flows, roads, rangeland, 

and vegetation management.

In subwatersheds with the highest vulnerability, any 

activity that maintains or increases water quantity or quality 

would ultimately be beneficial. In addition to roadwork, 

management actions to maintain or improve resilience could 

include contesting new water rights proposals, exploring 

ways to convert existing water rights into instream flows, 

improving conditions in grazing allotments, restoring 

natural function in meadows, and implementing silvicultural treatments aimed at moving toward more natural fire 

regimes. 

Results from WVA can also help guide implementation of travel management planning by informing priority 

setting for decommissioning roads and road reconstruction/

maintenance. As with the Ouachita NF example, disconnecting roads from the stream network is a key objective 

of such work. Similarly, WVA analysis could also help 

prioritize aquatic organism passage projects at road-stream 

crossings to allow migration by aquatic residents to suitable 

habitat as streamflow and temperatures change. 

Pilot forests in the Rocky Mountains recognized the 

utility of WVA results in selecting the subset of highvulnerability watersheds in areas with high pine beetle 

mortality. These areas are of high priority for upgrades 

of road-stream crossings to protect them from floods and 

debris flows. The same watersheds are also priorities for 

vegetation management to enhance natural reproduction, 

hydrologic recovery, stream shading, and future large 

woody debris recruitment. Both sets of actions would 

improve watershed condition and resilience. 

Not all the findings in the vulnerability assessments are 

good news. In some cases, projected changes may indicate 

that maintaining certain water resources (especially aquatic 

species) may be extremely difficult, even with restoration 

or improved management. In such cases, results from the 

vulnerability assessment may be used to rethink local or 

broad-scale improvement or protection strategies to prioritize limited management resources. 

The rating of vulnerability is based almost entirely on 

ecological considerations. Management activities are a key 

component in assessing watershed sensitivity, but only in 

terms of how they influence water resource values through 

hydrologic processes. Although such characteristics are 

significant, social, economic, and administrative factors 

may be more important in determining where management activities can be effectively undertaken. Such factors 

include availability of expertise, land ownership, the 

presence of willing partners, land and resource management planning guidance, and opportunities for internal 

or external funding. These factors need to be considered 

when determining where management activities should be 

focused.

Almost all the pilot forests encountered data gaps, and 

all encountered uncertainties during their analyses. Such 

data gaps (e.g., distribution of key species and uncertainty 

on road condition in key watersheds) can be used to identify 

inventory or monitoring priorities. Results from these 

efforts can, in turn, improve the utility of management and 

restoration plans. 
28

General Technical report pnw-gt r-884

It is noteworthy that the specific management activities 

discussed above, including road improvements, improving 

aquatic organism passage, thinning forests to improve stand 

resilience, and improving range condition, are not new 

treatments designed to address climate change. Rather, they 

are activities for which wildland resource managers have 

a long record of accomplishment. In land management and 

statutory jargon, they are established Best Management 

Practices (USDA FS 2012). Climate change increases the 

need for application of these practices nearly everywhere. 

Important Considerations in

Applying the Assessment Results

• Consider whether additional information, analysis, 

or consultation is needed before setting priorities.

• Identify approaches that can enhance resilience 

sufficiently to protect resource values.

• Consider which effects of climate change might 

be irreversible, and how that can inform priority 

setting. 

• In places where vulnerabilities are high, can 

resource values be sustained?

• Determine how management actions from 

watershed vulnerability assessment can be 

integrated into existing programs and priorities.

• Identify management practices that would enhance 

resilience in both the short and long term, and 

assess the magnitude of treatment that would be 

required to meet improvement objectives.

• Determine if land ownership patterns and 

administrative status of National Forest System 

lands are conducive to planning and implementing 

treatments.

• Identify areas where partnerships would improve 

the likelihood of success.

• Determine if sufficient technical and financial 

capacity is available to implement treatments.

Critique the Assessment

Test fast, fail fast, adjust fast.

—Tom Peters 

The purpose of the WVA pilot was to determine if worthwhile assessments could be conducted with available 

information and expertise. Within a relatively short period 

of time and despite limited funding and other pressing business, watershed and aquatic specialists from the pilot forests 

were able to develop a watershed-vulnerability approach 

and complete useful assessments. Four pilot forests were 

able to complete the process within 8 months, and an 

additional five were completed within a year. 

With an eye toward sharing approaches and experiences, each pilot forest was asked to critique its assessment. 

These reviews are key in applying the principles of adaptive 

management to the vulnerability assessments. In this final 

section, we discuss how access to information affected the 

assessments and share additional lessons learned by the 

pilots.

Data Gaps and Uncertainty

Assessing the sensitivity and vulnerability of watersheds to 

climate change is complex. At each step of the assessment 

process, pilot forests encountered data gaps and uncertainty. 

Uncertainty was prevalent in estimates of exposure, but 

each analytical step contained some uncertainty (e.g., 

the expected response of hydrologic processes to climate 

change, and the response of aquatic resources to the hydrologic change). 

Lack of information also contributes to uncertainty; at 

the least, it limits the detail of the assessment. Every pilot 

forest identified data needs, and each made assumptions 

about system responses and interactions. These were captured in the pilot reports as monitoring needs and included 

validating assumptions made in the assessment, tracking 

trends in key resource values, and providing data to inform 

key adaptive responses.

Acquiring and applying data to improve the analysis 

would produce assessments with a higher level of confidence, but lack of data should not be used as a reason for not 

conducting an assessment. Some pilot forests were data-
29

Assessing the Vulnerability of Watersheds to Climate Change

rich, in terms of water resource, watershed sensitivity, and 

exposure information, and some were data-poor. Despite 

these differences, all were able to apply the available information and complete a vulnerability assessment. Again, 

the objective of producing a relative rating of vulnerability 

(rather than a more rigorous, quantitative description of 

vulnerability) explains the favorable outcome. 

Other Lessons Learned

The pilot assessment effort was successful in that it demonstrated that vulnerability assessments could be completed 

by national forest staff using existing information and tools. 

Some of the primary reasons for this success have already 

been discussed; a few others are worth noting. 

Although we have discussed how availability of data 

influenced the results, we have not articulated the importance of the data format. National forests with digital data 

progressed much faster than those that had to convert paper 

summaries to digital formats. In some cases, lack of useable 

data caused elements of the assessment (e.g., sensitivity 

factors) to be deferred. Ideally, necessary data would be 

gathered and prepared in anticipation of assessments. A 

credible expectation that watershed vulnerability assessments will occur could help make this happen. 

Connection of the pilot forests with ongoing climate 

change research and experienced scientists resulted in 

a more detailed analysis. The partnership between the 

Sawtooth NF and RMRS yielded the most detailed pilot 

assessment. Collaborative work in downscaling climate 

change projections to assess potential changes in stream 

temperature was underway, and was well utilized by the 

Sawtooth. Connection to sources of exposure data (especially CIG) also aided pilot forests. 

As with most endeavors, the resulting products were 

strongly influenced by the experience and expertise of those 

participating. Participants with the greatest localized knowledge of forest resources and interactions tended to have the 

easiest time with the process. Use of the pilot participants as 

trainers or facilitators for future assessments would streamline and focus those efforts.

At the outset of the pilot project, several national forests 

declined to participate, owing to other priorities. The reality 

is that all participating national forests managed to work on 

the WVA despite heavy workloads. Agreeing to participate 

in the WVA process reflected recognition of the potential 

value of conducting WVAs. Pilot forests where line and 

staff were more engaged with the assessments made 

resources (interdisciplinary team members and geographic 

information system expertise) available to project leads, 

generally completed assessments sooner, and produced 

assessments of greater depth and detail.

Recently available electronic communication tools that 

facilitate information exchange proved extremely useful to 

the pilot effort. The pilot project applied both a collaborative Web space (a wiki bulletin board and a file repository) 

and videoconferencing to great advantage. Pilot leads were 

located across the country; monthly videoconferencing 

facilitated sharing of information and approaches, and 

helped cultivate a community of practice. The collaborative 

Web space proved a very effective means of sharing written 

information, publications, announcements, and Web links. 

The exchange of information enabled team members to 

learn from each other about processes and approaches that 

were working, and those that were posing difficulties. As 

a result, individual pilot efforts were strongly influenced 

The Forest Service 

Climate Change Resource Center

The Climate Change Resource Center (CCRC) 

(http://www.fs.fed.us/ccrc) provides land managers 

with an online portal to science-based information 

and tools concerning climate change and ecosystem 

management options. The CCRC’s objectives are to

• Synthesize scientific literature on ecosystem 

response, adaptation, and mitigation; 

• Highlight recent scientific research that has 

practical applications for practitioners on public 

and private lands; 

• Support communication of information through 

a user-friendly interface and appropriate use of 

multimedia; and 

• Work with scientists to develop educational 

resources.
30

General Technical report pnw-gt r-884

by each other. Readers who anticipate conducting an 

assessment are encouraged to contact members of the pilot 

assessment team, who can provide advice and counsel.

Finally, it is clear that establishing an analytical methodology was of great value. As the WVA pilots evolved, 

participants made modifications to meet their needs, but the 

basic approach provided a consistent framework for pilot 

forests to apply. The success of the pilots, which encompass 

a wide range of geographies, uses, and sensitivities, demonstrates that the conceptual basis of the approach is sound 

and likely applicable across the entire NFS. It will probably 

be applicable for all types of climate vulnerability assessments, not just water resources. Also of note is that we 

defined the component vulnerability terms at the outset, as 

this can be a source of confusion and unproductive debate; 

consistently sticking to and applying the terminology 

throughout the process assisted in moving the assessments 

forward. 

Summary

Observations clearly demonstrate that the Earth’s climate is 

warming and ecosystems are changing in response. Climate 

models predict substantial additional changes to worldwide 

temperatures and hydrologic processes throughout the 21st

century. These changes will have complex and variable 

effects on the Nation’s watersheds and affect their ability to 

sustain the ecosystem services upon which people depend. 

These effects pose significant challenges to the Forest 

Service and other land management agencies. To date, 

limited resources have been directed specifically towards 

planning for or responding to these changes on national 

forests and grasslands. This is largely because managers 

have limited experience applying global- or regional-scale 

climate change information at the local scale. This has 

led to uncertainties about likely impacts and appropriate 

responses for individual national forests or grasslands. 

To address this need, we implemented a Pilot Watershed Vulnerability Assessment Project that developed 

and tested a process that national forest personnel can use 

to complete useful, locally based assessments of water 

resource vulnerability to climate change. These evaluations 

followed a process patterned after watershed analysis on 

federal lands in the Pacific Northwest (USDA FS 1995). 

The assessments covered relatively large areas (e.g., entire 

national forests) with modest investments of time and effort. 

Regional climate projections, local historical data, and the 

Watershed Condition Classification recently completed by 

all national forests in the United States (http://www.fs.fed.

us/publications/watershed) provided a solid base of information to support the assessments.

In conducting the vulnerability assessments, forest 

staff became familiar with available historical climate data 

and climate projections for their geographic areas. Sorting 

through this information and learning how to use it was 

an important step in the process. Many forests found that 

partners had already compiled climate data and projections 

that could be used for the forest-level assessments. Knowing future climates precisely or accurately is not possible, 

but this was not a barrier to producing effective, efficient, 

informative assessments. 

In addition to climate data, the pilot assessments used 

existing information on watershed sensitivity and water 

resource values, data with which land managers are familiar 

and rely upon in many resource decisionmaking processes. 

The resulting assessments provided place-based identification of priority areas, with discernment of the watersheds 

most vulnerable and most resilient to climate change.

Assessing vulnerability is the essential first step in 

adapting to climate change, and this information provides a 

basis for managers to target investment of limited resources 

to sustain or improve watershed resilience. The good news 

is that the knowledge and tools to maintain and improve 

watershed resilience are already in place, while the National 

Watershed Condition Framework (USDA 2011a) serves as 

a foundation for setting priorities and restoring watersheds 

and watershed services. Other Forest Service programs to 

improve watersheds, meadows, and streams include diverse 

partners and programs across the country (Furniss et al. 

2010). Implementation of this wide array of management 

activities is supported by decades of technical experience in 

planning, analysis, and collaboration. These existing core 

strengths can be effectively applied to address the growing 

challenge to public natural resources posed by our changing 

climate.
31

Assessing the Vulnerability of Watersheds to Climate Change

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Appendix: Pilot National Forest Reports

The 11 pilot reports discussed in this report are available online only at 

http:/www.fs.fed.us/pnw/pubs/pnw_gtr884_appendix.pdf.
Pacific Northwest Research Station

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