The accumulating effects of human development are threatening water quality and availability. In recognition of the constraints to cumulative effects assessment (CEA) under traditional environmental impact assessment (EIA), there is an emerging body of research dedicated to watershed-based cumulative effects assessment (WCEA). To advance the science of WCEA, however, a standard set of ecosystem components and indicators is required that can be used at the watershed scale, to inform effects-based understanding of cumulative change, and at the project scale, to inform regulatory-based project based impact assessment and mitigation. A major challenge, however, is that it is not clear how such ecosystem components and indicators for WCEA can or should be developed. This study examined the use of aquatic ecosystem components and indicators in EIA practice in the South Saskatchewan River watershed, Canada, to determine whether current practice at the project scale could be "scaled up" to support ecosystem component and indicator development for WCEA. The hierarchy of assessment components and indicators used in a sample of 35 environmental impact assessments was examined and the factors affecting aquatic ecosystem component selection and indicator use were identified. Results showed that public environmental impact statements are not necessarily publically accessible, thus limiting opportunities for data and information sharing from the project to the watershed scale. We also found no consistent terminology across the sample of impact statements, thus making comparison of assessment processes and results difficult. Regulatory compliance was found to be the dominant factor influencing the selection of ecosystem components and indicators for use in project assessment, rather than scientific reasoning, followed by the mandate of the responsible government agency for the assessment, public input to the assessment process, and preexisting water licensing arrangements external to the assessment process. The current approach to project-based assessment offered little support for WCEA initiatives. It did not provide a standard set of aquatic ecosystem components and indicators or allow the sharing of information across projects and from the project to the watershed scale. We suggest that determining priority assessment parameters for WCEA requires adoption of a standardized framework of component and indicator terminology, which can then be populated for the watershed of concern based on both watershed-based priorities and project-specific regulatory requirements.
Keywords: Cumulative environmental effects; Environmental assessment; Indicators; Watershed cumulative effects assessment; Watersheds.
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