US EPA

Watersheds are frequently used to study and manage environmental resources because hydrologic boundaries define the flow of contaminants and other stressors. Ecological assessments of watersheds are complex because watersheds typically overlap multiple jurisdictional boundaries, are subjected to multiple environmental stressors, and have multiple stakeholders with diverse environmental and socioeconomic interests. Ecological risk assessment (ERA) is an approach that has successfully been used to increase the use of ecological science in decision making, by evaluating the likelihood that adverse ecological effects may result from exposure to one or more stressors, yet its application to watershed assessment is limited. This report supplements the Guidelines for Ecological Risk Assessmentby addressing issues commonly encountered when conducting watershed ecological assessments. Suggestions and examples to follow are provided based upon lessons learned from prior watershed ERAs. This report is of potential use to ecologists, hydrologists, watershed managers, risk assessors, landscape ecologists, and other scientists and managers seeking to increase the use of environmental assessment data in decision making. Each activity and phase of the watershed ERA process is explained sequentially in this report. Guidance on how to involve stakeholders to generate environmental management goals and objectives is provided. The processes for selecting assessment endpoints, developing conceptual models, and selecting the exposure and effects pathways to be analyzed are described. Suggestions for predicting how multiple sources and stressors affect assessment endpoints are also provided; these include using multivariate analyses to compare land use with biotic measurements. In addition, the report suggests how to estimate, describe, and communicate risk and how to evaluate management alternatives.

A watershed approach is frequently used to study and manage environmental resources. Ecological risk assessment (ERA) is a process for analyzing environmental problems and is intended to increase the use of ecological science in decision making in order to evaluate the likelihood that adverse ecological effects may occur or are occurring as a result of exposure to one or more stressors. Applying ERA principles at the watershed scale makes scientific information more relevant to the needs of environmental managers. Watershed ERAs are complex because addressing impacts from multiple sources and stressors on multiple endpoints presents a scientific challenge and because multiple stakeholders have diverse interests. The needs of managers and stakeholders may change, and the need to take action may require using the best available information at the time, sometimes before an ERA is completed. Therefore, at the watershed scale, flexibility on how to implement the ERA process is necessary. It is also important that risk assessors and managers interact regularly and repeatedly.

Each activity and phase of the watershed ERA process is explained sequentially in this report. Guidance on how to involve stakeholders to generate environmental management goals and objectives is provided. The processes for selecting assessment endpoints, developing conceptual models, and selecting the exposure and effects pathways to be analyzed are described. Suggestions for predicting how multiple sources and stressors affect assessment endpoints are also provided; these include using multivariate analyses to compare land use with biotic measurements. In addition, the report suggests how to estimate, describe, and communicate risk and how to evaluate management alternatives.

The purpose of this EPA report is to provide suggestions and examples for making scientific information more relevant to the needs of watershed managers by using ERA principles to help structure ecological assessments of watersheds.

This is the final report. The National Center for Environmental Assessment is currently determining the cause of biological impairments in watersheds through the Causal Analysis/Diagnosis Decision Information System (CADDIS) - http://cfpub.epa.gov/caddis/

U.S. EPA. Application of Watershed Ecological Risk Assessment Methods To Watershed Management. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-06/037F (NTIS PB2008-104486), 2008.