Watonwan Watershed Introduction

INTRO  |  Management Plan


HUC: 07020010

The Watonwan River Watershed is one of twelve major watersheds of the Minnesota River Basin. It is located within Blue Earth, Brown, Cottonwood, Jackson, Martin, and Watonwan counties in south central Minnesota. There are twelve municipalities in the watershed with St. James being the largest.

The Watonwan major watershed is approximately 561,620 acres (878 square miles), subdivided into 59 minor watersheds. The Watonwan River flows west from central Cottonwood County 113 miles to its confluence with the Blue Earth River 8 miles southwest of Mankato. Much of the river and its tributaries have been straightened and altered to provide for drainage of farmland and flood reduction. Wetlands and depressional areas have been altered and drained throughout much of the watershed for agricultural purposes. Higher flows in the area due to extensive drainage activities has led to increased erosion and higher sediment loads into surface water bodies



GIS data provided by the MN DNR and LCC-GIS Office

Main resource concerns in the watershed are wind and water soil erosion, nutrient management, and water quality.

Land Use

Agriculture is the predominant land use within the watershed, accounting for approximately 86% of the land use, followed by grass/pasture/hay (6%), and forest (2.75%). In general, two-year corn/soybean rotations comprise nearly 93% of the cropped lands within the watershed. Native vegetation in the area prior to settling was tall grass prairie.


GIS data provided by the MN DNR and MN Land Management CenterLanduselegend


97% Private Landowners
2.08% State
0.21% Private Major
0.09% Federal


Soils in the Watonwan watershed are primarily loamy glacial till with scattered lacustrine areas, potholes, outwash, and flood plains. It was formed during the Wisconsin glaciation in Minnesota with glacial till deposited from the Des Moines lobe. The landscape is nearly level to gently undulating with relatively short slopes.

The western half of the watershed lies primarily within the Blue Earth Till Plain. This portion of the landscape can be described as complex mixture of gently sloping (2-6%) well drained loamy soils and nearly level (0-2%) poorly drained loamy soils. Extensive use of artificial drainage to remove ponded water from flat and depressional areas can be found in this region of the watershed. Water erosion potential is moderate throughout much of the western half of the watershed.

The eastern half is a mixture of glacial lake plains, till plains, and moraines. This portion of the landscape can be described as nearly level with poorly drained or very poorly drained clayey or silty clay soils. Subsurface and surface tiling is extensive in this region of the watershed.


Picture provided by the USGS

The majority of the land in this area are not bordered by streams, lakes or drainage ditches, which means the water erosion potential is considered low throughout much of the eastern half of the watershed.

The western, southern, and eastern boundaries consist of end moraines formed by the last glaciation period. Soils are predominantly loamy in texture, ranging from steep and well-drained to nearly level and poorly drained. Much of the landscape can be described as undulating to hilly (2-12%) and approximately a quarter of these lands are adjacent to streams and ditches. Fifty percent of the cropped lands within this region have a high potential for water erosion.


The drainage network is defined by the Watonwan River and its major tributaries: North Fork of the Watonwan River, South Fork of the Watonwan River, St. James Creek, and Perch Creek; other smaller streams, public and private drainage systems, lakes, and wetlands complete the whole drainage network. Total length of the streams is 1,074 miles of which 685 miles are intermittent and 389 miles are perennial. Due to extensive artificial drainage through out the watershed, it is estimated that 86% of the wetlands were lost throughout the state.

Major Rivers and Streams
Watonwan River
North Fork of the Watonwan River
South Fork of the Watonwan River
Perch Creek
St. James Creek

Major Lakes
Mountain Lake
Wood Lake
Lake Hanska
Fish Lake

*More extensive lists of all rivers, streams, and lakes in the Watonwan watershed can be found at the MRBDC website*

Water quality information:
Monitoring stations have been established on the Watonwan River and some of the larger tributaries. Water quality data comes from a variety of sources, such as volunteers with the Citizen Stream Monitoring Program, USGS personnel, or MPCA personnel. You can find more information on water quality data from the MPCA interactive map. In general, of the three watersheds that make up the Greater Blue Earth River Basin, the Watonwan watershed generates the highest yield of total phosphorus (TP) and the highest yield of nitrate-nitrogen (N-NO3).

According to the MPCA website, the Watonwan River watershed had the following water quality estimations:

2007-2009 Watonwan – Average Loads, Concentrations and Yields
Results TSS Nitrate-Nitrogen TP PO4
Flow Weighted Concentration (mg/L) 70.6 7.96 0.23 0.133
Load (tons/yr) 21,653 2,361 64.77 38.46
Yield (lbs/acre) 87.65 9.56 0.26 0.16

For further information check out the MPCA website here to see more water quality data.

Water quality standards have been developed for many pollutants, and often they arise due to human health concerns. They are developed by state and federal governments to indicate the extent of the pollution in a water body. This gives us threshold to determine when waters are impaired or not.  The following are several of the key water quality standards for rivers:



Fecal Coliform Turbidity Nitrate-Nitrogen Dissolved Oxygen Total Phosphorus* TSS
Water Quality Standard 200 CFU/100 mL 25 NTU 10 mg/L 5 mg/L none ~60 mg/L
*There is no federal or state standard for phosphorus, often it is dependent upon and specific to the water body; The Minnesota River is estimated that a threshold of 0.26 mg/L is needed to reduce undesirable algal growth; EPA desired goal to prevent nuisance plant growth is 0.1 mg/L


Resource Concerns

Many of the waters in the Watonwan watershed are on the MPCA impaired waters list. The major concerns are aquatic recreation, aquatic consumption, and aquatic life caused by high levels of turbidity, nutrients, and bacteria.


Listed Stream/Reach


Affected Use

Watonwan River, North Fork: Headwaters to Watonwan River Turbidity Aquatic Life
Watonwan River, South Fork: Butterfield Creek to S Fk Watonwan Fish IBI, Fecal Coliform, Turbidity Aquatic Life, Aquatic Recreation
Watonwan River, South Fork: Willow Creek to Watonwan R Fecal Coliform*, Turbidity Aquatic Life, Aquatic Recreation
Watonwan River: Headwaters to N Fk Watonwan R Fish IBI, Fecal Coliform, Turbidity Aquatic Life, Aquatic Recreation
Watonwan River: N Fk Watonwan R to Butterfield Creek Fecal Coliform*, Turbidity, Aquatic Life, Aquatic Recreation
Watonwan River: Perch Creek to Blue Earth R Fecal Coliform*, Turbidity, Mercury Aquatic Life, Aquatic Consumption, Aquatic Recreation
Watonwan River: S Fk Watonwan R to Perch Creek Turbidity Aquatic Life
Watonwan River: Butterfield Creek to S Fk Watonwan R Fish IBI, Fecal Coliform*, Turbidity Aquatic Life, Aquatic Recreation
Perch Creek: Headwaters to Spring Creek Turbidity Aquatic Life
St James Creek: Headwaters to Kansas Lk Turbidity Aquatic Life
Butterfield Creek: Headwaters to St James Creek Turbidity Aquatic Life
Listed Lake Impairment Affected Use
Mountain Mercury* Aquatic Consumption
Fish Mercury* Aquatic Consumption

*Approved TMDL

Check out the MPCA Environmental Data Access for more information.

Soil Quality

Sheet and Rill erosion cause sediment delivery to water bodies and remove productive topsoil from agricultural areas. It also increases the potential for gully formation.

Wind erosion physically removes lighter, less dense soil constituents such as organic matter, clays, and silts. This removes the fertile part of the soil and can lower productivity.

Surface Water Quality

Excess nutrients, sediment, and bacteria in surface water bodies degrades water quality and affects aquatic life and recreation.

Groundwater Quality

Nutrients, organics, and animal and human waste pose potential water quality and health issues for groundwater from aging septic systems, feedlot runoff, agricultural runoff, and abandoned wells.


Links for more Information about the Watonwan Watershed

MPCA Watonwan Watershed
MRBDC Watonwan Watershed

EPA Surf Your Watershed

MN DNR Watershed Assessment Tool

Reports and Publications concerning the watershed and/or basin

Watonwan One Watershed, One Plan
Watonwan-One-Watershed-One Plan Appendix

Watonwan River Major Watershed Diagnostic Report
Watonwan Watershed Summary

Watonwan Rapid Watershed Assessment

Watonwan River Watershed Phase IIB Project Implementation – Final Report 2000-2008

Watonwan Impaired Waters Map

Minnesota River Basin: Watonwan, Blue Earth, and Le Sueur River Watersheds