Watonwan River

Watershed at a Glance

The Minnesota River: Evaluating its health [highlight]


The Watonwan River watershed area is approximately 878 square miles (561,620 acres). The Watonwan watershed is one of the 12 major watersheds of the Minnesota River Basin. It is located in south-central Minnesota within Blue Earth, Brown, Cottonwood, Jackson, Martin, and Watonwan counties. There are 12 municipalities in the watershed of which the city of St. James is the largest.

The Watonwan River rises in central Cottonwood County and flows 113 miles through flat farmland in northern Watonwan and western Blue Earth counties, past the city of Madelia, until it flows into the Blue Earth River about 8 miles southwest of Mankato. Much of the river has been straightened and altered to provide for drainage of farmland and for flood reduction.

The Watonwan River offers a peaceful and scenic float for paddlers until the rapids generally increase as the river nears its confluence with the Blue Earth River above the Rapidan dam. In Madelia, Watona Park is nestled along the banks of the Watonwan River and features many amenities, including a campground.

Hydrologic Unit Code:07020010
Intensive monitoring start year:2013
Major lakesMajor rivers and streams
Hanska, Wood, Mountain
Watonwan, St. James Creek, Perch Creek


Much of the river has been straightened and altered to provide for drainage of farmland and for flood reduction. Though the vast majority of the Watonwan watershed is used for farming, mainly corn and soybeans, small lakes and wetlands provide significant habitat for waterfowl.

Like most areas of the Minnesota River Basin, the soils in the Watonwan River watershed are highly erodible. Changes in climate and changes in the landscape have resulted in higher flows in the river system. The combination of erodible soils and higher flows has led to greater levels of erosion and a dramatic increase in sediment levels in the river system since European settlement in the late 1800s. Sediment makes the water cloudy and hurts aquatic life such as fish.

The Watonwan River, along with the LeSueur River, are the Blue Earth River's largest tributaries. Together, these watersheds make up the Greater Blue Earth River Basin, which drains 5,540 square miles (2.3 million acres) in 11 counties in Minnesota and three in Iowa.

By volume, the Blue Earth is the Minnesota River's largest tributary, accounting for 46 percent of the Minnesota's flow at the rivers' confluence. It also a major contributor of sediment to the Minnesota River. In the Greater Blue Earth River Basin, 39 sections of streams and rivers fail to meet the state water quality standard for turbidity, meaning the water is too cloudy and affects aquatic life such as fish.

Under state standards, the level of Total Suspended Solids for rivers in the basin should be 90 parts per million. However, levels average between 175 to 675 parts per million, far above the levels needed for clear water, according to water monitoring from 2000-2008.

Several stretches of streams in the Greater Blue Earth River also have bacteria levels high enough to violate the state water quality standard, indicating they are not suitable for swimming and other body-contact recreation. Restoring these streams will require reducing bacteria levels by 80 to 90 percent.

    What's being done

    The MPCA has finished intensive water monitoring of the Watonwan watershed and plans to publish a report on this effort in 2016. As part of this project, the agency has also started work to identify stressors hurting water quality and conditions fostering healthy waters. In addition, the MPCA, Greater Blue Earth River Basin Alliance, and Water Resources Center-Mankato are gathering input from citizens in the watershed through interviews and events.

    The MPCA is working with local partners, focusing on feedlots and failing septic systems, to reduce bacteria levels and make streams suitable for swimming and other body-contact recreation. As part of the Minnesota River Basin, the Blue Earth and its tributaries have been the subject of several scientific studies, including research by the MPCA, WRC-Minnesota State University-Mankato, University of Minnesota, National Center for Earth Surface Dynamics, Minnesota Department of Agriculture, and others.

    The MPCA and several other agencies monitor the water quality of the rivers and streams in the watershed, an effort that spans more than 20 years.

    The MPCA and Water Resources Center of Minnesota State University-Minnesota are finalizing a Total Maximum Daily Load report for the Greater Blue Earth River Basin. In this report, the MPCA recommends a 0% reduction in sediment levels during low flow conditions and a 92.7% reduction during high flow conditions such as spring thaw. After the report goes on public notice and receives approval from the U.S. Environmental Protection Agency, the MPCA and Water Resources Center will work with stakeholders and scientists to develop an implementation plan to guide restoration.

    Monitoring and assessment reports and data

    PDF icon Watonwan Watershed Monitoring and Assessment Report (wq-ws3-07020010b)

    PDF icon Watonwan River Watershed Hydrology, Connectivity, and Geomorphology Assessment Report (wq-ws3-07020010d)

    HSPF model documentation

    PDF icon Model resegmentation and extension for Minnesota River watershed model applications

    PDF icon Hydrology and water-quality calibration and validation of Minnesota River watershed model

    PDF icon Watonwan River HSPF Summary (wq-ws3-07020010c)

    What is a watershed?

    Illustration showing contour of land directing flow of water

    Learn the basics of a watershed.

    Water Resources Center

    184 Trafton Science Center S.
    Minnesota State University - Mankato
    Mankato, MN 56001

    Dustin Anderson
    GBERBA technician for Watonwan County
    339 9th St.
    Windom, MN 56101
    507-831-1153, ext. 3