Watonwan River
The Watonwan River in Garden City (2007).
The Watonwan River in Garden City Township, Blue Earth County ( 1996)
The Watonwan River is a 182 km long tributary of the Blue Earth River in southern Minnesota. About this and the Minnesota River, it is part of the catchment area of the Mississippi River and drains an area of 2274 km ². The Watonwan River accounts for about a quarter of the catchment area of the Blue Earth River.
Geography
The Watonwan River rises in Amboy Township, about 5 km southwest of Jeffers in the center of Cottonwood County and flows generally eastward over over flat Moränenebenen through the north of the Watonwan County and the west of the Blue Earth County, in the town of Madelia. It flows about 13 km south-west of Mankato, or 26 km above its confluence with the Minnesota River in the Blue Earth River.
The largest tributaries of the river are South and North Fork Watonwan River. The 118 km long South Fork Watonwan River rises in the southeast of Cottonwood County and initially flows eastward to the south of Watonwan County and touches briefly the Martin County, as well as Odin. Then the South Fork runs northeastward through the eastern part of the Watonwan County to the confluence with the Watonwan River above Madelia. The 63- km-long North Fork Watonwan River rises in Cottonwood County and flows eastward to the north of Watonwan County and flows approximately two kilometers southeast of La Salle in the Watonwan River.
About 84 % of the catchment area of the Blue Earth River, which includes the Watonwan River is used for agriculture, mainly for the cultivation of corn and soybeans. Smaller lakes and wetlands provide habitat for waterfowl in Minnesota though large sections of the river and its tributaries were transformed by ditches and canals.
Runoff
The United States Geological Survey operates a level near the Garden City township, about 12 km upstream of the river mouth. The measured there 1940-2005 water level was an annual average of 11 m³ / s The highest recorded value was 394 m³ / s were on 20 June 1993, the lowest value a few dm ³ / s, which was caused by an ice barrier on 28 December 1989.