The Clearwater River Watershed covers 886,600 acres (1,384 square miles) of northwestern Minnesota. About one third of the watershed lies within the Lake Agassiz Plain Ecoregion – a flat area with fertile soils formed by Glacial Lake Agassiz. As a result, a substantial amount of land (33%) within the watershed is utilized for intensive row crop farming. Another 21% of the land is used for pasture and hay (rangeland). The remainder of the watershed lies within the Northern Minnesota Wetlands Ecoregion (NMW), North Central Hardwood and Forests Ecoregion (NCHF), and Northern Lakes and Forests Ecoregion (NLF). Forests and wetlands are interspersed with cropland throughout the watershed but are more prevalent within the eastern portion. The most expansive wetland area is located in the northeast corner of the watershed; this area is located within the Red Lake Indian Reservation. Major rivers within the Clearwater River Watershed include the Clearwater River, Lost River, Hill River, and Poplar River. Other smaller tributaries within the watershed include Lower Badger Creek, Ruffy Brook, Silver Creek, and Beau Gerlot Creek. Extensive ditching and other hydrologic alterations have occurred within the Clearwater River Watershed. Numerous ditches and drain tiles convey water from agricultural land to rivers and streams. These hydrologic alterations, combined with the loss of historic wetlands and conversion of native prairie to farmland, contribute to frequent flooding in the watershed. Major lakes within the watershed include Clearwater Lake, Pine Lake, Maple Lake, and Kiwosay Pool. In 2014, the Minnesota Pollution Control Agency (MPCA) began an intensive watershed monitoring (IWM) effort of lakes and streams within the Clearwater River Watershed. Thirty-nine stream sites were sampled for biology at the outlet of variable sized subwatersheds. As part of this effort, MPCA staff joined with local partners to complete stream water chemistry sampling on 15 stream reaches. In 2016, lakes and streams with sufficient data to make an assessment were assessed for aquatic life, aquatic recreation, and aquatic consumption use support. During this process, 32 stream segments were assessed for aquatic life and 28 segments were assessed for aquatic recreation. Thirty-two lakes were assessed for aquatic recreation and nine lakes were assessed for aquatic life. Twelve stream segments fully supported aquatic life. The remaining 20 segments did not support aquatic life and were determined to be impaired. Fifteen of the segments assessed for aquatic recreation were found to be impaired. Eight aquatic life impairments were the result of poor fish and/or macroinvertebrate communities. Most biological impairments were attributed to poor habitat caused by unstable stream channels and widely varying flow regimes. The unstable stream channels had poor channel development and contained excess fine sediment that covered coarse substrate. Some impairments appear to be the result of excess dissolved oxygen (DO) flux and/or low DO. Hydrologic alterations within the watershed have resulted in a loss of base flow in some systems. The loss of base flow allows for greater DO flux which is a stressor to aquatic life. Barriers to fish passage, such as improperly installed/sized culverts and beaver dams, were also a cause of biological impairments within the Clearwater River Watershed.
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Minnesota Pollution Control Agency (St. Paul, Minnesota)
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Minnesota Pollution Control Agency