EPA estimates the benefits of preserving aquatic resources using the water quality index (WQI). The WQI focuses on metrics related to human use, such as recreation, but fails to fully capture aspects important to nonuse values of aquatic ecosystems, such as existence values. Stated preference surveys can quantify the nonuse values of streams and lakes but require an appropriate index of biological health to be able to measure and compare biological condition.

In a recent effort, EPA researchers identified an appropriate biological health index to be applied in a forthcoming national stated preference survey that will estimate nonuse values of streams and lakes throughout the conterminous United States (CONUS). Through a literature review and focus groups, researchers compared two aquatic indices that are regularly used to quantify biological health by EPA’s National Aquatic Resources Surveys: 1) multimetric indices (MMIs) and 2) the observed-to-expected ratio of taxonomic composition (O/E). This webinar will discuss this comparison, implications for estimating benefits of preserving aquatic resources, and forthcoming work to link O/E with water quality and habitat models, which would forecast changes in O/E resulting from future regulatory action.