Draft Little Fork River Watershed Sediment Reduction Project (Total Maximum Daily Load)

This report addresses four stream segments in the Little Fork River Watershed that are impaired due to excess sedimentation (turbidity). Excess sedimentation affects waterbodies' ability to sustain a healthy aquatic eco-system. The federal Clean Water Act (CWA) requires a process to identify, analyze, and correct water problems. This is called a Total Maximum Daily Load (TMDL) study. The TMDL identifies the pollutant that is causing the problem and establishes the maximum amount of the pollutant an impaired waterbody can receive on a daily basis and still meet water quality standards. The TMDL also identifies the sources of the pollutant and methods and practices that can be undertaken to alleviate the problem. A holistic approach was taken to monitor and assess the surface water bodies (i.e., streams, lakes) in the Little Fork RiverWatershed to determine if they meet water quality standards for aquatic life use, recreation use, and consumption use. Fifty-four locations were sampled for biology at the outlets of subwatersheds of varying sizes in the Little Fork RiverWatershed. Forty-three stream segments in the watershed (Assessment Unit Identifier (AUIDs)) were assessed for aquatic life use. Thirty-seven of the forty-three stream segments fully support aquatic life use. The remaining six segments did not support aquatic life use and were determined to be impaired. In five of these impaired segments, the cause was determined to be excess turbidity (or sediment) in the water. In the sixth segment, the impairment was determined due to a poor fish community. Of the six impaired segments, two are being deferred at this time and will be addressed during Cycle 2 of the Watershed Restoration and Protection Strategies (WRAPS) process in the Little Fork RiverWatershed, starting in 2018. One of the deferred segments (AUID 09030005-502, the Little Fork River from Lost Lake to Rice River) is impaired for aquatic life use by turbidity (or sediment). There was conflicting data from the four biological monitoring stations along this stretch of river and it was determined, by the local partners, that this segment should be studied further. The other deferred segment (AUID 09030005-517, the Rice River from Johnson Creek to the Little Fork River) is impaired for aquatic life use due to a poor fish community. Of the three biological stations in this segment, one of the stations (station number 05RN010) had conflicting information. Local partners decided to develop a comprehensive monitoring plan for further investigation. In this report, the following sediment sources are evaluated for each impaired stream: watershed runoff, loading from upstream waterbodies and tributaries, channel erosion, near bank erosion, streambed erosion, and point sources. An inventory of pollutant sources was used to develop a load duration curve (LDC) model for each impaired stream. This model was then used to determine the sediment reductions needed for the impaired streams to meet water quality standards. Sediment reduction Best Management Practices (BMPs) can be deployed in many places throughout the watershed to begin to make reductions in the overall numbers. These reduction projects must achieve large percentages of reductions in order to meet the total suspended solids (TSS) standard for rivers in the Northern Lakes and Forest eco-region, 15 mg/L. Due to the geology and soils of the watershed, it is understood that these reductions will be very difficult. The findings from this TMDL study were used to aid the selection of implementation activities as part of the Little Fork RiverWRAPS process. The purpose of the WRAPS report is to support local working groups and jointly develop scientifically supported restoration and protection strategies to be used for subsequent local implementation planning. The WRAPS report is publically available on the MPCA Little Fork RiverWatershed website: https://www.pca.state.mn.us/water/watersheds/little-fork-river
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Minnesota Pollution Control Agency (St. Paul, Minnesota)
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Minnesota Water Research Digital Library
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Creative Commons