Lake Superior South Watershed Stressor Identification Report

This report summarizes the principal causes, or "stressors," contributing to impaired fish and aquatic macroinvertebrate communities in three streams within the Lake Superior South 8-digit HUC watershed (Beaver River, West Branch Beaver River, and Talmadge River). Ultimately, the results of this report will be used to guide several processes, including; total maximum daily load (TMDL) development; defining the need for research and development of new water quality standards; and prioritizing additional monitoring, restoration, and protection strategies in these watersheds. A wide-range of potential stressors were evaluated in order to increase confidence in the stressor diagnosis. Ultimately, five stressors were identified within the Lake Superior South HUC with high confidence; elevated total suspended solids (TSS), low dissolved oxygen (DO), elevated water temperatures, poor physical habitat conditions, and altered hydrology (lack of baseflow). An additional three stressors remain potential candidate causes of impairment; loss of connectivity (e.g. perched culverts), elevated ionic strength, and elevated pH. These were either unable to be eliminated based on inconclusive results, or were localized impacts in need of attention but not a prominent cause of the impaired condition. The stressor identification results for the three impaired streams are summarized below.