Le Sueur River

Watershed at a Glance

The Minnesota River: Evaluating its health [highlight]


Located in south central Minnesota, the Le Sueur River flows 111 miles through a gently rolling landscape, most of it farmland, until it cuts down through high bluffs to the Blue Earth River. The Le Sueur, which is named for a French explorer, starts in Freeborn County, flowing north and west through parts of Waseca and Blue Earth counties. It passes through the city of St. Clair, which is near the regional hub of Mankato. Tributaries from Steele and Faribault Counties also flow into the Le Sueur. A total of 711,838 acres drain to the Le Sueur, and an extensive ditch and tile system facilitates movement of water throughout the watershed. Several streams (a total of 1,201 miles) flow to the Le Sueur, with its major tributaries being the Cobb and Maple rivers.

Hydrologic Unit Code:07020011
Intensive monitoring start year:2008
Major lakesMajor rivers and streams
Eagle, Madison, Lake Elysian, Freeborn, Minnesota, Lura, Rice, Bass, St. Olaf
Le Sueur, Big Cobb, Little Cobb, Maple, Rice Creek, Beuford Ditch


Once covered with hardwood forests and long-grass prairies, the vast majority of the watershed is now planted to crops such as corn and soybeans or used for livestock production. Lakes and wetlands currently comprise 3% of the watershed. About 89% of the wetlands have been drained since European settlement. Many of the lakes are shallow and provide wildlife habitat while others are deeper and popular for recreation. For paddlers, the Le Sueur River offers a twisting route from St. Clair through Hungry Hollow and joins the Blue Earth River near the Red Jacket Bridge, which is part of a popular bike trail. This part of the river offers many spectacular cliffs and lots of wildlife.

Water monitoring shows some modest improvements in water quality in the Le Sueur River over the past 10 years, though several sections of the river and its streams continue to suffer from many problems, including turbidity, low dissolved oxygen, and excess nutrients. The Le Sueur watershed is a major source of sediment and nutrients to the Minnesota River. Several agencies and universities have studied the watershed over the past three decades with research continuing. With so much data available for this watershed, agencies and stakeholders can begin targeting work to reduce the pollutants in the watershed, clearing up the water for local residents and improving water quality downstream all the way to the Mississippi River.

    What's being done

    The MPCA conducted intensive watershed monitoring in the Le Sueur River Watershed in 2008, with the results showing the location and severity of water quality problems.

    The MPCA sampled the fish population in 82 sites in the Le Sueur River watershed in 2008. Researchers found that species tolerant of high turbidity, such as fathead minnows and common carp, dominated the fish population, though game fish were present in 41 percent of the sites. With a reduction in sediment and other pollutants, the rivers and streams in the watershed could support more species that are sensitive to turbidity, such as smallmouth bass and darter species.

    Assessing the biology of streams in the watershed is difficult because of the extensive changes in the watershed. To use the land for farming and urban development, land owners have extensively built drainage ditches, installed drainage tile, and straightened streams to move water off the land faster. The MPCA will consider a different type of assessment for these altered streams in the future.

    In this first cycle of intensely studying the watershed:

    • Of the 11 lakes examined in the watershed, two supported aquatic recreation — St. Olaf and Reeds. Five were impaired due to high nutrient levels, and four need more data to determine their status.
    • Of the 74 stream sections examined, only one — in the Cobb River — supported aquatic life. Twenty-one were impaired and 12 need more data to determine their status. Forty have been altered significantly so the MPCA is deferring assessment.

    Under federal and state laws, impaired waters must have Total Maximum Daily Load (TMDL) studies to determine reductions of pollutants needed to again meet water quality standards. In this first WRAPS cycle, the MPCA completed TMDL studies for four lakes and six stream sections. In addition to these lakes and stream sections, the MPCA has completed a TMDL study for Lura Lake in the watershed and is working to complete a TMDL study of turbidity in the Le Sueur River as part of the greater Blue Earth River system.

    Clean Water Act Accountability Report

    Monitoring and assessment reports and data

    Strategy reports

    Local partners

    What is a watershed?

    Illustration showing contour of land directing flow of water

    Learn the basics of a watershed.

    Minnesota State University Mankato-Water Resource Center


    Blue Earth County Environmental Services


    Blue Earth County SWCD


    Faribault County SWCD


    Freeborn County SWCD


    Freeborn County Environmental Services


    Waseca County SWCD


    Waseca County Planning and Zoning


    Greater Blue Earth River Basin Alliance