Ecological risk assessment as a watershed management tool -- Case study of middle Snake River, Idaho

Ecological risk assessment is a scientific tool designed to evaluate the ecological effects of human activities. Historically, risk assessments have been used as a tool to assess risks to human health from environmental exposures to toxic pollutants, or to assess the ecological effects of toxic releases. The middle Snake River has been used as one of five EPA case studies to demonstrate the applicability of risk assessment at the watershed level for assessing the relative effects of multiple stressors on key ecological components of the aquatic ecosystem. The state and federal resource managers and the public identified restoration and protection of native cold water salmonid species and rare and endangered invertebrate species as a management goal. The risk assessment sought to characterize the significance of reduced water flow, sedimentation, and increased nutrients on these ecological components through a process of problem formulation, stressor-effects analysis, and risk characterization. The desired outcome of the assessment is to identify conditions that must be attained to support the management goal as one step in evaluating management options for ecological protection in the watershed.