Great Rivers Partnership - River Science: Bioreactors Help Clean up Minnesota Stream

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There's an experiment going on in southeast Minnesota. One that could help protect and restore water quality in the Root River and other tributaries to the Mississippi River, while keeping agriculture economically viable.

The Root River, which is rich in mussels, insects and other aquatic life, flows through a largely agricultural landscape.

Surface and subsurface drainage systems, used to move excess water off agricultural fields, are causing soil erosion along stream banks. They also put excessive amounts of nitrogen and phosphorus in the Root and its tributary streams, which can damage water quality and aquatic habitat.

Letting Nature Do the Work

In September, The Nature Conservancy launched a project to minimize some of the negative impacts of agricultural drainage systems.

Working with two farm families near Ostrander and Grand Meadow, Minnesota, and several state and local agencies, the Conservancy installed infiltration ponds and bioreactors on marginal farmland along two tributary streams to the Root.

Runoff from nearby farm fields is directed into the infiltration ponds where native vegetation filters out pollutants before the water is slowly released. After the water leaves the ponds, it enters the bioreactors — buried trenches loaded with woodchips. Bacteria on the woodchips remove nitrates from agricultural runoff. The treated water is then directed into a ditch that leads to the South Branch of the Root River.

Sharing Lessons Learned

The Conservancy and the Mower County Soil and Water Conservation District are monitoring the quality of the water entering the infiltration basins and leaving them either through conventional drainage lines, the bioreactor drainage lines or an overflow structure (during high water periods).

The partners will present their methods and results to the Natural Resources Conservation Service for use in a technical paper that can be shared with staff and interested agricultural landowners in the region.

"We are doing this project in such a way that we can measure our results," said Rich Biske, the Conservancy's Blufflands Conservation Coordinator.

"If we're successful, then we can help our partners and others work with farmers and install more of these drainage systems and return the Root and other Mississippi River tributaries to a more natural condition."

The Monsanto Company and the Kellogg Foundation funded the project. Additional partners include the Minnesota Department of Agriculture, Mower County Soil and Water Conservation District, the South Branch of the Root River Partnership and the University of Minnesota's Southwest Research and Outreach Center in Lamberton.

Questions can be directed to Rich Biske at (507) 765-2450 or via email.