South Fork Crow River Watershed Characterization Report

The South Fork Crow River watershed is an eight-digit Hydrologic Unit Code (HUC) watershed draining approximately 1,279 mi2 of predominantly agricultural land in south-central Minnesota. The following report analyzes the hydrology, connectivity, and geomorphology components of the South Fork Crow River watershed. Historical gage data on the South Fork Crow River, stream crossing data, and applied fluvial geomorphology assessments were analyzed to characterize conditions of the watershed and find relationships to help understand water quality and biological impairments throughout the watershed. Assessment of current and historical aerial photography indicated extensive channel modification and channelization throughout the watershed. According to the Minnesota Pollution Control Agency (MPCA), 90.4% of the South Fork Crow River watershed watercourses have been altered (e.g., channelized or impounded). Channelized systems have limited floodplain connectivity and are often incorrectly sized (e.g., cross sectional area to drainage area, width/depth ratios), not allowing the channel to effectively transport the sediments of its watershed. Rivers and streams in the South Fork Crow River watershed that are still able to access their floodplains and dissipate energy during high flows are showing greater signs of stream stability and habitat quality. However, altered hydrology is currently a significant driver of geomorphic change, water quality degradation, and habitat loss. Precipitation and discharge data indicated the amount of water delivered per inch of precipitation has increased over time. This increased volume of water delivery can further destabilize the rivers and streams of the watershed and is a contributing factor to the geomorphic response within the watershed.