Preliminary Analysis of Thresholds for Determining Aquatic Life Use Attainment Status in the Upper Mississippi River Mainstem
This project identified "potential impairment thresholds for the UMR main channel in determining the attainment of aquatic life uses," as identified in the project work plan. To that end, biological thresholds were developed for early review by the UMRBA Water Quality Task Force (WQTF) in January 2011. The initial analyses relied upon data gathered and research performed by the U.S. EPA EMAP-GRE program to assess aquatic life use attainment within the already established CWA assessment reaches established by the five UMR states for the Upper Mississippi River mainstem. Specific project tasks included:
1) examining alternate approaches to establishing thresholds using the EMAP-GRE indices beyond the three condition classes developed by GRE; 2) comparing GRE-based thresholds to those developed using alternate approaches and indices, including a reference condition-based approach; 3) further exploration of the sensitivity of the GRE suite of indices and other available indices to a set of stressor gradients; and, 4) evaluating the inclusion of a submersed vegetation index into a UMR bioassessment.
Various statistical methods were used to derive CWA thresholds for the indices examined and the appropriateness of those thresholds in light of aquatic life use attainment realities in the UMR main channel. As such this report produce a first time assessment of the UMR main channel utilizing biological data as the arbiter of CWA goal attainment.