|- elevation 1,653 ft (504 m)|
- average 381 cu ft/s (11 m/s)
Basin area 3,401 km²
Basin area 3,401 km²
Country United States of America
|- elevation 794 ft (242 m)|
Length 245 km
Discharge 11 m³/s
Source Rock Lake Township
Mouths Minnesota River, New Ulm
|- location Rock Lake Township, Lyon County|
- location near New Ulm, Brown County
- max 28,700 cu ft/s (813 m/s)
The Cottonwood River is a tributary of the Minnesota River, 152 miles (245 km) long, in southwestern Minnesota in the United States. Via the Minnesota River, it is part of the watershed of the Mississippi River, draining an area of 1,313 square miles (3,400 km2) in an agricultural region. The river's name is a translation of the Sioux name for the river, Waraju, for the cottonwood tree, which is common along prairie rivers. It has also been known historically as the Big Cottonwood River.
Map of Cottonwood River, Minnesota, USA
The Cottonwood River flows generally eastwardly throughout its course. It rises southwest of Balaton in Rock Lake Township in southern Lyon County, as an intermittent stream on the Coteau des Prairies, a morainic plateau dividing the Mississippi and Missouri River watersheds. The river flows off the Coteau in a wooded valley in southeastern Lyon County, dropping 200 feet (60 m) in five miles (3 km), and enters a region of till plains, flowing through southern Redwood County, the northeastern corner of Cottonwood County, and northern Brown County, past the communities of Sanborn and Springfield. It enters a wooded valley near its mouth, flowing through Flandrau State Park and entering the Minnesota River just southeast of New Ulm. The river was formerly dammed to form a lake in the state park, but the dam was not rebuilt after being washed out by floods in 1965 and 1969.
Due to the northeastward slope of the Coteau des Prairies and the presence of a terminal moraine along the northern side of the river, very few tributaries enter the Cottonwood River from the north. The largest is Sleepy Eye Creek, 51 miles (82 km) long, which flows eastwardly through Redwood and Brown Counties, past Cobden. Tributaries from the south include Plum Creek, 35 miles (56 km) long, which flows northeastwardly through Murray and Redwood Counties, past Walnut Grove; and Dutch Charley Creek, 46 miles (74 km) long, which flows northeastwardly through Murray, Cottonwood, and Redwood Counties.
Approximately 84% of land in the Cottonwood River watershed is used for agriculture; the predominant crops are corn and soybeans. Wetlands in the watershed have been extensively drained, and fewer than 4,000 acres (16 km²) remain.
At the United States Geological Survey's stream gauge near New Ulm, 3.2 miles (5.2 km) upstream from the river's mouth, the annual mean flow of the river between 1909 and 2005 was 381 cubic feet per second (11 m³/s). The highest recorded flow during the period was 28,700 ft³/s (813 m³/s) on April 10, 1969. The lowest recorded flow was 0.5 ft³/s (0 m³/s) on November 27, 1952.