Applying Ecological Risk Principles to Watershed Assessment and Management

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FORUM

Applying Ecological Risk Principles to Watershed

Assessment and Management

VICTOR B. SERVEISSU.S. Environmental Protection Agency (8623-D)

1200 Pennsylvania Ave., NW

Washington, DC 20460

ABSTRACT / Considerable progr ess in addressing point

source (end of pipe) pollution problems has been made, but

it is now recognized that further substantial environmental

improvements depend on controlling nonpoint source pol-

lution. A watershed approach is being used more frequently

to address these problems because traditional regulatory

approaches do not focus on nonpoint sources. The water-

shed approach is organized around the guiding principles

of partnerships, geographic focus, and management based

on sound science and data. This helps to focus efforts on

the highest priority problems within hydrologically-defined

geographic areas. Ecological risk assessment is a process

to collect, organize, analyze, and present scientific informa-tion to improve decision making. The U.S. Environmental

Protection Agency (EPA) sponsored three watershed as-

sessments and found that integrating the watershed ap-

proach with ecological risk assessment increases the use

of environmental monitoring and assessment data in deci-

sion making. This paper describes the basics of the water-

shed approach, the ecological risk assessment process,

and how these two frameworks can be integrated. The

three major principles of watershed ecological risk assess-

ment found to be most useful for increasing the use of sci-

ence in decision making are (1) using assessment end-

points and conceptual models, (2) holding regular

interactions between scientists and managers, and (3) de-

veloping a focus for multiple stressor analysis. Examples

are provided illustrating how these principles were imple-

mented in these assessments.

Considerable progress in addressing point source

(end of pipe) pollution problems has been made but it

is now recognized that further substantial environmen-

tal improvements depend on controlling nonpoint

source pollution (US EPA 1996). Pollution and habitat

degradation problems can best be solved by using abasin-wide (watershed) approach rather than working

with an individual waterbody or discharger (US EPA

1996). The Watershed Approach Framework (US EPA

1996) is organized around the guiding principles of

partnerships, geographic focus, and management

based on sound science data. It is a framework for

coordinating environmental management that focuses

public and private sector efforts on addressing the high-

est priority problems within hydrologically-defined geo-

graphic areas, taking into consideration both ground

and surface water flow. Instead of using the more tra-

ditional pollutant-by-pollutant approach, the watershedapproach incorporates a comprehensive strategy which

enables those who must live with environmental deci-

sions to participate in making them. Federal agencies

are using the watershed scale as they place increased

emphasis on community- and placed-based approaches

for environmental protection (US EPA 1996, Maxwell

1998). In addition, many states have implemented wa-

tershed restoration action strategies in response to the

Clean Water Action Plan (US EPA 1998a). These strat-

egies focus management actions on geographic regions

rather than on specific media (e.g., air, water).

Efforts on a watershed scale rely heavily on voluntary compliance, stakeholder involvement, and an under-

standing of the cumulative impact of multiple physical,

chemical, and biological stressors over a broad range of

spatial scales. Consistently incorporating science in wa-

tershed management decisions, however, is challenging

because the data needs for watershed-scale decision

making are complex. Multiple physical, chemical, and

biological stressors may co-occur due to human activi-

ties and natural causes. These stressors, when com-

bined with a network of interrelated environmental

conditions, may cause diverse impacts on numerous

ecological resources. Even when the science is under-stood, it remains difficult to use science in watershed

management decisions because the watershed typically

overlaps multiple jurisdictional areas, is managed by

organizations with divergent goals and responsibilities,

and contains numerous stakeholders with their own

self-interests. Tradeoffs among environmental, politi-

cal, economic, and social factors based on subjective

value judgements occur as part of the decision process.

As a result, valuable data from many monitoring and

assessment efforts frequently do not play a major role in

KEY WORDS: Watershed management; Ecological risk assessment;

Watershed assessment; Water quality management; En-

vironmental assessment; Environmental decision making

DOI: 10.1007/s00267-001-0025-z

Environmental Management Vol. 29, No. 2, pp. 145–154 © 2002 Springer-Verlag New York Inc.


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management decisions (Ward and others 1986, Ward1996). Helpful suggestions and frameworks have beendeveloped to improve various aspects of watershedmanagement and to improve the use of ecological sci-ence in place-based decision making (Ward and others1986, Slocombe 1993, MacDonald 1994, Armitage

1995, US EPA 1996, US EPA 1998b, Rhoads and others1999, Timmerman and others 2000).

One framework that appears to be helpful to water-shed management is ecological risk assessment (Serveiss and others 2000), a process to collect, orga-nize, analyze, and present scientific information. It isdescribed in detail in EPA ’s Guidelines for Ecological Risk Assessment (US EPA 1998b). The ecological risk assess-ment process consists of three phases (Figure 1): prob-lem formulation, risk analysis, and risk characterization(US EPA 1998b). EPA ’s risk assessment guidelines have

been applied successfully and used extensively insource- and pollutant-based approaches (such as thosefocused on particular chemical contaminants), yet theirapplicability to place-based approaches (such as thoseconducted on a watershed-wide scale) is still limited(US EPA 2000). Ecological risk assessment can use

partnerships, a geographic focus, and sound science toenable States, local governments, and watershed coun-cils to prioritize problems and take appropriate actions.It is an iterative process which includes a regularly occurring dialogue between scientists and managers, asrepresented by the “arrows” in Figure 1. These interac-tions take on greater importance in a watershed assess-ment with multiple stressors, pathways, ecological re-sources, and self-interests. Applying ecological riskassessment within a watershed approach can provide

watershed management groups a logical and systematic

Figure 1. Framework for Eco-

logical Risk Assessment (US

EPA 1998b).

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method to incorporate scientific information into de-cision making (Serveiss and others 2000).

The strengths of the Watershed Approach are itsemphasis on a naturally defined geographic area, onpartnerships, and stakeholder involvement and on bas-ing decisions on sound science. The strength of eco-logical risk assessment is in providing specific advice onhow to develop, analyze, and present scientific informa-tion so that it can best inform management decisions.

The integration of the watershed approach with eco-logical risk assessment, hereafter called watershed eco-logical risk assessment, achieves the collective benefitsof both frameworks. Table 1 summarizes the valuableand complementary linkages between the watershedapproach and ecological risk assessment.

This paper describes how watershed ecological riskassessment can be used to select, analyze, integrate, andpresent environmental data so that it is most useful for

watershed assessment and management. It builds onprinciples articulated in the Watershed ApproachFramework (US EPA 1996) and Ecological Risk Assess-

ment Guidelines (US EPA 1998), and draws on experi-ence from three EPA sponsored watershed assessments.These watershed assessments demonstrate the value of using three key principles of watershed ecological riskassessment: developing assessment endpoints and con-ceptual models, holding recurring interactions be-tween scientists and managers, and developing a focusfor performing multiple stressor analysis. This paperdiscusses the value of using these watershed ecologicalrisk assessment principles and provides examples of how they were applied. While the emphasis is on using

these principles for watershed ecological assessments,many elements of this process also apply to other place-based management efforts directed at improving hu-man health and environmental quality.

Introduction to Three Watershed EcologicalRisk Assessments

Three watershed assessments, funded by EPA, are dis-cussed in this paper: Clinch and Powell Valley, Virginia;

Waquoit Bay, Massachusetts; and Big Darby Creek, Ohio. All three watersheds have valued ecological resources,multiple stressors, an existing data set, and participants

willing to perform the assessment. Table 2 lists the water-sheds, existing human activities and associated stressors,the valued ecological resources and the assessment end-points examined, the approach used for multiple stressor

analysis, and environmental management actions that arebeing implemented or considered.The free-flowing segment of the Clinch and Powell

Rivers flow southwesterly through southwestern Vir-ginia and into Norris Lake in Tennessee. The basincovers 9,971 square km and contains one of the most diverse and unique assemblage of fish and freshwatermussel species in North America. Activities such asmining, agriculture, and urbanization are likely causesof reductions in fish and mussel species richness andthe cause of many species being listed as threatened orendangered. The Nature Conservancy has establishedthe Clinch Valley Bioreserve to conserve biological di-

versity in the watershed. Waquoit Bay is a shallow estuary on the south coast of

Cape Cod, Massachusetts. Its watershed covers about 53square km, fed by groundwater and freshwater streams,salt ponds and marshes, pine and oak forest, barrierbeaches, and open estuarine waters. The bay, along withadjoining marshes, tidal rivers, and barrier beaches, pro-

vides an ideal habitat for plant and animal life. Urbaniza-tion is changing the landscape and contributing nutrientsand contaminants to the bay. The area has been desig-nated as a National Estuarine Research Reserve and an

Area of Critical Environmental Concern.

The Big Darby Creek watershed is an example of ahigh-quality ecosystem in the agricultural Midwest. The

watershed encompasses 1443 square km (557 square mi)in central Ohio and is highly valued for its scenic beauty,its high water quality, and for recreational opportunities.Big Darby Creek and its tributaries are home to an excep-tional variety of species, especially a unique assemblage of rare and endangered freshwater mussel and fish species.The central issues facing the Big Darby watershed arefuture land use and implementation of best management practices for urban and agricultural runoff. A large por-

Table 1. Integrating the watershed approach with

ecological risk assessment

Elements of the watershed approach

Linkages to ecological riskassessment

Geographic focus The scope of the assessment isidentified in during problemformulation

Continuous improvement based on soundscience

The analysis and riskcharacterization phasesprovide and organizescientific informationrelevant to management decisions

Partnership andstakeholderinvolvement

Interactions with managersand stakeholders areemphasized during problemformulation and riskcharacterization phases,communication during the

analysis phase is alsoencouraged

Applying Ecological Risk to Watersheds 147


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tion of Big Darby Creek is an Ohio State Scenic River and

a National Wild and Scenic River. The Nature Conser- vancy has designated it one of the “Last Great Places” inthe western hemisphere.

Experiences from these three assessments demon-strate that following watershed ecological risk assess-ment principles increases the likelihood that environ-mental monitoring and assessment data are consideredin decision-making. The three major principles that proved most beneficial, are: (1) holding regular meet-ings between scientists and managers, (2) using assess-ment endpoints and conceptual models, and (3) devel-oping a focus for the multiple stressor analysis.

Principle 1: Value of Regular Interactions

Between Scientists and Managers

Many recent recommendations have emphasizedthat stakeholder and manager involvement needs to beinitiated in the planning step, and recurring rounds of deliberations and analysis are necessary throughout theprocess to make the findings most useful (NRC 1996,Foran and Ferenc 1999, US EPA 2000, Timmerman andothers 2000). As part of the planning activity for a

watershed ecological risk assessment, scientists and

managers agree upon the expected output and thetechnical and financial resources to be used for per-

forming the assessment. Managers need to describe why the risk assessment is needed, its relevance to

regulations, and their plans for using the findings. Sci-entists need to communicate to managers what they

can realistically provide, where problems are likely, and where uncertainty may arise. After the risk assessment

starts, new information obtained through literature review, field data, peer review, or managers awareness of

environmental changes may trigger iterative loops. Thisfeedback loop is intended to incorporate new scientific

information and changing risk management needs intothe developing risk assessment. This section provides

information and examples of how such initial and reg-ular interactions helped focus the three assessments

and provided more meaningful assessment findings.Managers need to agree upon clearly articulated wa-

tershed management goals. Elements of existing goal

statements from watershed councils, conservation plans,or local growth planning strategies should be incorpo-

rated where appropriate. Managers and scientists shouldelaborate on the goals by developing a set of measurable

Table 2. Descriptions of three watershed ecological risk assessments

Location andsize Human activities/stressors

Valued ecologicalresources/analyzed

assessment endpoints

Process foranalyzing multiple

stressors

Environmental management actions being implemented or

considered

Upper Clinchand PowellRiversa

Mining, forestry,agriculture,spills/sediments, andtoxic substances

Fish and mussels/reproductionandrecruitment of threatened fishand musselspecies

Multivariateanalysescomparingsources, landuses, and effects

Protect riparian corridors,more monitoring of coalmining operations, spillcontrol mechanisms, best management practices forpasture and agricultural land

Waquoit Bay b Septic tanks, atmosphericdeposition/nitrogen,toxics

Scallops and fish/abundance of eelgrass,macroalgae andphytoplankton

Nitrogen loadingand effectsmodel

Zoning controls, septic tanktreatment options, buildinga sewage treatment plant

Big Darby Creekc

Agriculture,urbanization/sediments,nutrients

Fish and mussels/speciescomposition,diversity andfunctionalorganization of the fish andbenthicmacroinvertebratecommunities

Multivariateanalysescomparingsources,stressors, andeffects

Reducing erosion, designatingareas with the best aquaticbiological conditions as aNational Wildlife Refuge,re-targeting erosion controlefforts

aSouthwestern Virginia, 9,971 km2.bCape Cod, MA, 53 km2.cCentral Ohio, 1443 km2.

148 V. B. Serveiss


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models are especially valuable in watershed assessmentssince they describe the multiple physical, biological,and chemical stressors in a system and their sources,and the pathways by which they are likely to impact

multiple ecological resources (Suter 1999). The predic-tions made by these models serve as qualitative hypoth-eses that may be helpful for decision making. Thesepredictions may be used to prioritize problems andhelp address Total Maximum Daily Load (TMDL) is-sues. TMDLs are pollution budgets to reduce loadingsof pollutants that exceed water quality criteria.

In the Clinch Valley assessment, maintaining listedthreatened and endangered fish and mussel species is amanagement objective. Their reproduction and recruit-ment is of ecological importance (and potentially affected

by the stressors of concern). Therefore, the assessment endpoints for this risk assessment are: (1) reproductionand recruitment of rare, threatened, and endangered fishspecies and (2) reproduction and recruitment of rare,

threatened, and endangered mussel species.Figure 2 shows the conceptual model for threatened

and endangered mussel species. The lines show thephysical, chemical, and biological stressors that stemfrom each human activity (source) and the many envi-ronmental changes that could result from these stres-sors. For example, urban, agricultural, livestock, andsilviculture operations all modify the riparian buffer(top right of figure). Riparian modification is one of fi ve major stressors shown that cause a series of envi-ronmental changes that indirectly affect the mussel

Figure 2. Clinch and Powell

assessment: Reproduction, re-

cruitment of threatened, en-

dangered or rare mussel spe-

cies (US EPA 2002).

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species of concern. Only those pathways considered

most ecologically important by the workgroup are

shown to keep the presentation manageable.

Conceptual models can be prepared to include

more details. For instance, the Big Darby Creek con-

ceptual model shows the appropriate biological mea-sures that are used to assess impacts from stressors

(Cormier and others 2000). Macroinvertebrate organ-

isms belonging to the orders Ephemoptera (may fl y),

Trichoptera (caddisfl y), and Plecoptera (stonefl y) species

are relatively pollution intolerant (Lenat 1984). Thus, a

lower number of these species indicates impacts from

sediments, toxic input, altered stream morphology, or

an altered hydrologic regime.

The selected assessment endpoint for this study was

the species composition, diversity, and functional orga-

nization of the fish and benthic macroinvertebrate

communities (Cormier and others 2000). Reasons forselecting this endpoint include: (1) Ohio EPA water

quality standards specifically link water quality to the

ability of a stream to support and maintain species

composition; (2) this endpoint is impacted by stressors

from the activities of concern, particularly agriculture

and urbanization; and (3) the stream community struc-

ture and function is ecologically related to broader

issues such as ecological integrity (Karr and Chu 1999).

In Waquoit Bay, the assessment helped stakeholders,

scientists, and managers identify collectively the most

significant ecological concern in the watershed: i.e.,

impact of nitrogen on eelgrass and ultimately fish (Va-liela and others 2000). In Waquoit Bay, the conceptual

model shows how excess nitrogen input may exert ef-

fects on a commercial fishery indirectly by causing algal

blooms that reduce light levels to the point that eelgrass

(a submerged aquatic plant important as habitat for

juvenile fish) cannot survive. In this case, habitat loss is

the stressor impacting the fish, but knowledge of the

whole chain of events is necessary to take cost-effective

corrective action. Eelgrass abundance was selected as

an assessment endpoint because of its ecological impor-

tance, susceptibility to the stressor of primary concern

(excess nitrogen input), and relevance to a manage-ment objective (restoring native fish populations).

Thus, an advantage of conceptual models is that they

consider and describe cascading effects which may not be

immediately apparent. The conceptual model is also a

powerful communication tool; the one developed for the

Waquoit Bay, for example, is on display at the National

Estuarine Research Reserve. In all three assessments,

group efforts to develop the conceptual model were par-

ticularly valuable for communicating expectations within

the technical workgroup and to stakeholders.

Principle 3: Developing a Focus for Multiple

Stressor Analysis

The analysis phase of risk assessment seeks to estimate

(1) exposure, the extent to which assessment endpoint

resources are exposed to the stressors resulting from hu-man activities; and (2) effects, the effects likely to occur as

a result of exposure. Several analyses may be performed

or considered. Cause and effect relationships need to be

established or postulated based on observed effects (e.g.,

fish kill following a pesticide application), experimental

or laboratory data, or statistical associations. In watershed

assessments, spatial and temporal distributions of both the

assessment endpoint and the stressors need to be consid-

ered. During the risk characterization phase, exposure

and effects analyses are integrated into an overall estimate

of risk and used as “lines of evidence” to reach a final

conclusion about the likelihood and the consequences of effects.

Because watershed-scale multiple-stressor risk assess-

ments are complex, not all required data for performing

the exposure and effects analyses may be available. Differ-

ent stressors may co-occur in different places; some may

occur only episodically, making them dif ficult to quantify

and interpret. Furthermore, the cumulative effect of co-

occurring stressors is often not known. Ideally, the stres-

sor-response relationship will relate the magnitude, dura-

tion, frequency, and timing of exposure in the watershed

to the biological effects. However, detailed quantitative

exposure information is often unavailable due to the rel-atively large spatial scale and the multiple stressors that

could be present. Furthermore, there may be problems

combining data from many sources, especially if collected

for another purpose. The technology is not yet available

and data requirements are too enormous to develop

quantitative associations between sources (e.g., agricul-

ture), stressors (e.g., impaired water quality, sediments,

and toxic substances), and effects in a watershed with

complex systems and pathways.

For watershed ecological risk assessments, exposure

and effects estimates may need to be aggregated or the

analyses may need to be limited to the most disruptive

stressor. Given the aformentioned limitations, it may be

most useful to first examine relationships between land

use and biological data because both of these types of

information are often relatively reliable and available.

Exposure information may then be inferred from dif-

ferent land uses based on available data in the water-

shed and information from the literature. Examining

the relative intensity or extent of certain land uses in

relation to available biological data may also help es-

tablish exposure-effects relationships.



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In the Clinch Valley assessment, data on environ-mental stressors, their sources, and mussel and fish data

were entered into a graphical information system(GIS). Using the conceptual model, hypotheses con-cerning source stressor-effect relationships were devel-

oped and tested using multivariate statistics. Stepwisemultiple regression analyses of land uses with fish indexof biotic integrity (IBI) indicated that 55% of the vari-ance in fish community integrity scores could be ex-plained by certain land use categories (Diamond andServeiss 2001). Further analyses demonstrated that fishIBI was inversely related to both the number of activemining facilities in a subwatershed and to proximity tomining activities. These analyses along with other liter-ature provided lines of evidence to strongly suggest certain stressor-effect relationships. Maps and cumula-tive stressor-response curves were especially useful in

visualizing cumulative sources of stress in relation tolocations of threatened and endangered mussel species which could then be used to evaluate vulnerability andprioritize management strategies.

Pilot projects using subwatersheds may also be useful(MacDonald 1994) to explore analytical approaches. TheClinch Valley assessment studied two subwatersheds. Thefirst watershed was used to confirm that fish IBI could beused as a surrogate measure for mussel species richnessand to define the optimal size of upstream area for com-paring land use with biological effects. The second sub-

watershed was used to quantify uncertainties in this pro-cedure (see Suter 1998 for discussion of uncertainties). In

addition, the geographic focus and scope of the analysismay need to be altered to get suf ficient data or reducecosts, as was the case in the Big Darby Creek assessment.To better define the relationships between stressor andeffect, it was determined that the geographic scopeneeded to be expanded to the entire Eastern Corn Belt Ecoregion.

The Big Darby Creek assessment sought associationsbetween stressors and impacts (Norton and others2000). The analysis of risk is retrospective in that itsconclusions relied on current and past land use prac-tices and biological measurements taken at specific

sites. Researchers used the index of community integ-rity for macroinvertebrates (DeShon 1995) and theindex of biotic integrity (Karr 1981) for fish to repre-sent ecological status within stream segments in the

watershed. Multivariate analyses were used to deter-mine relationships between index results, instreamstressors, and land use patterns in the watershed. Theanalysis identified components of the community that

were associated with specific types of stress. For exam-ple, the percent of Tanytarsini midges and Glypotendipes increased at sites having low and high biological oxygen

demand, respectively. The percent of darters increased

at sites having high scores for stream corridor structureand low concentrations of inorganic nutrients.

The Waquoit Bay assessment focused on one stres-sor, nitrogen, that is the predicted cause of much of the

impact on valued ecological resources and for whichmanagement control options exist (Valiela and others

2000). Models were developed to clarify the pathways of how nitrogen reached the bay, and to predict ecologi-

cal impacts at various exposure levels.

Discussion

A major challenge when dealing with multiple non-point source stressors is to obtain useful scientific in-formation to help consider, evaluate, and select options

for environmental management. This paper has de-scribed how the watershed approach can be integrated

with ecological risk assessment to improve environmen-tal management decision making. Examples from three

watershed assessments illustrate the use of a model or

statistical investigation to identify associations betweenland use and impacts. Whether using these or other

approaches, biological monitoring data are very helpfulin identifying the biological and ecological conse-quences of human actions and provide an essential

foundation for assessing ecological risks (Karr and Chu1999). Identifying risks and areas in need of protection

may help managers obtain grants and assistance from

various water resource programs. With the informationin hand, managers may be able to petition for regula-

tion of previously unregulated activities. In addition,risk characterization may provide the reasonable assur-

ance required to show whether a TMDL will attain thestate-adopted water quality standard.

Through watershed ecological risk assessment, sci-

entists and managers interact more, helping scientistsunderstand the technical needs of the decision-makers

and managers to better understand the ecological im-plications of their actions. This dialogue offers numer-ous benefits for those faced with the challenge of struc-

turing environmental monitoring and analysis effortsand using such data for decision-making. The process

increases the likelihood that (1) the optimal suite of scientific data is collected, analyzed, and considered;(2) monitoring, analysis, and restoration decisions are

made that reflect management goals, along with theinterests and most valued ecological concerns of stake-

holders; and (3) ecological and hydrological processes which impact those resources are considered.

The benefits of applying the integrated watershedrisk assessment approach are described in a review

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funded by the Water Environment Research Federation(Butcher and others 1997) and include:

● The risk assessment framework can add significant value to watershed-scale management programsparticularly when addressing problems caused by

multiple and non-chemical stressors.● Formal and scientifically-defensible methods of risk

assessment help prioritize and evaluate risk.● While best professional judgement may arrive at the

same conclusions as an ecological risk assessment,the process helps people to carefully examine what led them to their conclusions and document their

findings.

Well-structured assessments already contain many ele-ments of watershed ecological risk assessment, without a

specific reference or cognizance that risk assessment prin-ciples are being used. For instance, a retrospective analysisof work done by the Chesapeake Bay Program shows that

the ecological risk assessment paradigm has been effec-tively applied to the Chesapeake Bay ’s clean-up effort (deFur 1997). Although many watershed communities donot have the financial resources, technical expertise, nor

necessary data to conduct a comprehensive risk assess-ment, these groups can still derive benefits from using

watershed ecological risk principles.The usefulness of a risk assessment is enhanced

when scientists and managers communicate regularly

throughout the process. Bringing scientists and manag-ers together to develop management objectives andagree upon the scope, purpose, and complexity of anassessment enables them to develop a common vision,

share information, and understand socioeconomic andecological concerns. Scientists and managers shouldmeet periodically to discuss interim findings and mod-ify the thrust of analysis efforts based on the intermit-

tent deliberations These communications will ulti-mately increase the likelihood that the data collectedand the manner by which they are analyzed and pre-sented will increase their use in decision-making.

A conceptual model improves the understanding of how valued ecological resources are affected by physi-cal, chemical, and biological stressors caused by humanactivities. Selecting assessment endpoints provides alink between choosing what to analyze and achieving

management objectives. An analysis plan provides sci-entific justification for deciding which data to collect,and how to analyze and present results. Completing thisportion of the ecological risk process can yield valuable

qualitative information to help participants better un-derstand the sources and pathways through which stres-

sors impact valued ecological resources. This also helps

to compare, rank, and prioritize risks.

Based on the few watershed ecological risk assess-

ments done to date, the most challenging aspect is

analyzing the impacts of multiple human activities and

stressors that may vary over time and space. Some re-cent research on deciphering effects of multiple stres-

sors provides useful tools (Landis and Wiegers 1997,

Wiegers and others 1998, Foran and Ferenc 1999, Dyer

and others 2000, Norton and others 2000). These pa-

pers indicate it is useful to simplify the analytical ap-

proach in a watershed setting by using a categorical

ranking system, or focusing on the impacts of selected

stressors, or by using multivariate analysis to describe

associations between sources or stressors and effects.

Developing conclusions based on integrating multiple

lines of evidence and discussing the degree of certainty

in the findings makes the results more meaningful.Using ecological risk principles, such as the ones dis-

cussed in this paper, provides managers with the ability to

incorporate more scientific information into their water-

shed management plans, thereby enabling them to better

understand the system and make more informed deci-

sions. Documenting the impacts to valued ecological re-

sources and the importance of protecting them helps

justify taking actions and assists with selecting the most

cost-effective restoration or control action. Even without

direct regulatory authority, environmental improvements

can be attained because increased awareness resulting

from documenting the consequences of human activitieson the environment encourages positive behavioral

changes and management actions.

Acknowledgments

Jerry Diamond, William van der Schalie, Susan Norton,

Barry Tonning, James Andreasen, Doug Norton, Patricia

Cirone, Randy Bruins, Robert Coats and anonymous re-

viewers provided helpful input or comments. The author

also thanks the many participants of the three watershed

assessments, in particular, Don Gowan, Roberta Hylton,

David Dow, Ivan Valiela, Jennifer Bowen, and Susan Nor-ton. The views expressed in this paper are those of the

author and do not necessarily reflect the views or policies

of the U.S. Environmental Protection Agency.

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