09/25/2025
Agassiz Pool, in Agassiz National Wildlife Refuge, receives flow from the Thief River and Mud River, then discharges to the Thief River. The Thief River then flows to Thief River Falls. Both rivers carry sediment into the pool, where it is deposited. The sedimentation has led to excess cattail growth and has been detrimental to waterfowl habitat. Seasonal drawdowns of the pool, in turn, send high concentrations of sediment and nutrients downstream to the drinking water source for the City of Thief River Falls. Flooding is a concern in the area, as well, especially along the State Ditch 83 portion of the Thief River.
A Flood Damage Reduction Project Work Team approach was used to develop the Mud River Enhancement Project. The team of agency staff and landowners came to a consensus on a project that will will direct water into a meandering 6-mile channel which would bring riparian function to the original channel by restoring the natural process and improve the migratory bird habit by designing a nature-based channel to convey incoming flow from the Mud River. Instead of being directly deposited in the remnants of JD 11 channel within Agassiz Pool (from which much sediment can be flushed downstream), sediment can be deposited on a 700 acres of floodplain that is currently inaccessible due to the excavation of JD 11 that occurred in the early 1900s. The new channel will roughly follow the path of an ancient channel (currently buried under 5 feet of peat) that staff discovered using aerial photography and soil borings. The meandering channel and floodplain enhancement will improve aquatic habitat and improve waterfowl habitat. It will reduce the impacts of runoff events upon over-water nesting birds in Agassiz Pool by moderating inflows. Upstream sediment runoff from thousands of acres of agricultural lands and ditches is being reduced through best management practices that are being largely funded by Thief River Watershed-Based Implementation Funding (One Watershed One Plan implementation) from the Minnesota Board of Water and Soil Resources (BWSR).
The Mud River Project Team's discussions led to the development of a subsequent project team that is currently working on solutions to flooding along State Ditch 83 downstream of Agassiz National Wildlife Refuge. The Red Lake Watershed District has committed $500,000 towards construction and has applied for $5.1 million in funding from the Lessard-Sams Outdoor Heritage Council.
