Watonwan River

The Watonwan River is a 113-mile tributary of the Blue Earth River in south-central Minnesota. It rises in Amboy Township, about 3 miles southwest of Jeffers in central Cottonwood County. From there it flows generally east across flat farmland through northern Watonwan and western Blue Earth counties, past Madelia. It joins the Blue Earth River about 8 miles southwest of Mankato, above the Rapidan dam. Its watershed covers about 878 square miles and is one of 12 major watersheds of the Minnesota River Basin. The river's largest tributaries are its North and South forks. Much of the river has been straightened and altered for farm drainage and flood reduction. At the U.S. Geological Survey gauge near Garden City, the annual mean flow from 1940 to 2005 was 391 cubic feet per second.

The Watonwan was established as a Minnesota state water trail in 1996. The Minnesota DNR describes it as usually calm but sometimes fast-flowing, with no major rapids and occasional snags. A 30-mile segment from Madelia to the Blue Earth River confluence at Garden City is a common paddling route. Blue Earth County manages the ramps at Co Rd 20, Co Rd 32 and Garden City, as well as the Blue Earth County Fair carry-in access. The City of Madelia operates a carry-in access, and the DNR Division of Parks and Trails runs the Hwy #169 carry-in. Madelia's Watona Park, on the river, has a canoe launch. Minnesota's statewide aquatic invasive species laws apply, including draining all water and removing drain plugs before leaving an access.

The river's original name, Watanwan, means "where fish bait abounds" in Dakota. Members of the Younger brothers of the James–Younger Gang were captured near Madelia in 1876.