Of the 379 protected lakes and basins greater than four hectares (ten acres) within the Crow Wing Watershed, the trophic status of 111 lakes were assessed to determine if the lakes supported aquatic recreation. One hundred four of the assessed lakes supported aquatic recreation and seven lakes did not support aquatic recreation and are considered impaired. The impaired lakes are small to moderately sized lakes with large watershed catchment areas making them susceptible to high levels of external nutrient contributions. Most notably, First Crow Wing, Lower Twin and Blueberry Lakes each have catchment areas greater than 100,000 acres. In addition to external nutrient contribution, several of the impaired lakes were shallow and likely receive additional nutrients from suspended bottom sediments. Internal loading of nutrients is most likely in Margaret, Portage, Lower Twin, Blueberry and First Crow Wing Lakes. Assessment data were available on an additional nine wetlands and reservoirs; however, the basin characteristics and/or residence times did not qualify them to be assessed as lakes. Rivers and streams were assessed for aquatic life and aquatic recreation. Throughout the Crow Wing Watershed, 32 stream Assessment Unit Identification Determination (AUIDs) were fully supporting for aquatic life and 13 streams are fully supporting for aquatic recreation. Eighteen AUIDs were non-supporting of aquatic life and/or recreation. Of those AUIDs, nine were non-supporting of aquatic life and ten were non-supporting of aquatic recreation. The aquatic life impairments were due to low fish and macroinvertebrate Index of Biotic Integrity (IBI) scores and or low dissolved oxygen (DO). None of the assessed streams within the Crow Wing Watershed were impaired for turbidity. Notable impairments include the Straight River and Shell River for DO while the Upper Crow Wing River, Cat River, Farnham Creek, Partridge River and Swan Creek were impaired for aquatic recreational use due to high bacteria levels.
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Minnesota Pollution Control Agency (St. Paul, Minnesota)
Minnesota Pollution Control Agency