Watonwan Watershed Introduction

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Overview

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 Center

Ownership:

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

Soils/Geology

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.

Hydrology

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:

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:

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.

Check out the MPCA Environmental Data Access for more information.

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