Cooperative Fish and Wildlife Research Units Program: all
Education, Research and Technical Assistance for Managing Our Natural Resources

A comprehensive understanding of the prevalent impairments in reservoirs is necessary nationally to analyze patterns and allocate national resources effectively. Many of these impairments are associated with sedimentation, nutrient contamination, and other pollution factors. The costs involved in performing on-site surveys of multiple locations are a potential obstacle in obtaining empirical data on impairment at a large spatial extent. In this case, input from specialists may be required to tackle the absence of empirical data that is required to determine the impairment status of thousands of geographically dispersed reservoirs. Our aim was to assess if expert opinion could offer a comprehensive view of the impairment status of reservoirs in the conterminous United States. We designed and executed an internet-based survey of reservoir specialists to get their rating of visually evident elements of reservoir impairment. To evaluate the ratings, we searched for correlations with factors known to have an impact on reservoir impairment. Canonical correlation analyses indicated that nine metrics, which were used by experts to rate impairment levels in an ordinal scale, were correlated with metrics descriptive of physical qualities of the reservoirs, land use in catchments, and the prevailing local climate. We conclude that expert opinion may facilitate assessment of impairment levels over large geographic areas. Lastly, we define the circumstances under which it is permissible to rely on expert opinion and propose criteria that may improve the quality of the data collected.