Lac Courte Oreilles, Couderay River Watershed (UC20)
Lac Courte Oreilles, Couderay River Watershed (UC20)
Lac Courte Oreilles (2390800)
5139.54 Acres
Natural Community
Natural communities (stream and lake natural communities) represent model results that use predicted flow and temperature based on landscape features and related assumptions. Ranges of flow and temperature associated with specific aquatic life communities (fish, macroinvertebrates) help biologists identify appropriate resource management goals. Wisconsin Natural Communities.
Year Last Monitored
This is the most recent date of monitoring data stored in SWIMS. Additional surveys for fish and habitat may be available subsequent to this date.
This lake is impaired
Low DO
Unknown Pollutant
Trout Water 
Trout Waters are represented by Class I, Class II or Class III waters. These classes have specific ecological characteristics and management actions associated with them. For more information regarding Trout Classifications, see the Fisheries Trout Class Webpages.
Outstanding or Exceptional 
Wisconsin has designated many of the state's highest quality waters as Outstanding Resource Waters (ORWs) or Exceptional Resource Waters (ERWs). Waters designated as ORW or ERW are surface waters which provide outstanding recreational opportunities, support valuable fisheries and wildlife habitat, have good water quality, and are not significantly impacted by human activities. ORW and ERW status identifies waters that the State of Wisconsin has determined warrant additional protection from the effects of pollution. These designations are intended to meet federal Clean Water Act obligations requiring Wisconsin to adopt an 'antidegradation' policy that is designed to prevent any lowering of water quality - especially in those waters having significant ecological or cultural value.
Impaired Water 
A water is polluted or 'impaired' if it does not support full use by humans, wildlife, fish and other aquatic life and it is shown that one or more of the pollutant criteria are not met.

Fish and Aquatic Life

Current Use
The use the water currently supports. This is not a designation or classification; it is based on the current condition of the water. Information in this column is not designed for, and should not be used for, regulatory purposes.
Shallow headwater lake describes the depth and location of the lake in a watershed. These variables affect the lakes response to watershed variables.
Attainable Use
The use that the investigator believes the water could achieve through managing "controllable" sources. Beaver dams, hydroelectric dams, low gradient streams, and naturally occurring low flows are generally not considered controllable. The attainable use may be the same as the current use or it may be higher.
Supported Aquatic Life
Waters that support fish and aquatic life communities (healthy biological communities).
Designated Use
This is the water classification legally recognized by NR102 and NR104, Wis. Adm. Code. The classification determines water quality criteria and effluent limits. Waters obtain designated uses through classification procedures.
Default FAL
Fish and Aquatic Life - Default Waters do not have a specific use designation subcategory but are considered fishable, swimmable waters.

Historical Description

Source: 1969, Surface Water Resources of Sawyer County Lac Court Oreilles, T39, 40N, R8, 9W,

A soft water, drainage lake having a normal estimated outlet Of 25.0 cfs flowing into Little Court Oreilles Lake on the Couderay River. It is of the largest natural lakes in the state. It has a varied fish population of northern pike, walleye, muskellunge, largemouth bass, smallmouth bass, bluegill, perch, black crappie, rock bass, pumpkinseed, and brown and yellow bullheads. Cisco are also abundant and lake trout have been recently stocked. Other fish species present include longnose gar, white suckers, and minnow species. Competition between northern pike and muskellunge has been a management problem here. Northern pike, apparently recently, have introduced expanded at the sacrifice of muskellunge. All the streams flowing into the lake are non-trout waters. The shoreline is predominately upland pine with steep bluffs in many places; however, nearly 500 acres of predominately bog wetlands provides habitat for waterfowl. Muskrats are also common. Private development amounts to 14 resorts, five boat rentals, 206 cottages, and the facilities of four private fishing clubs. Three commercial cranberry marshes utilize water from the lake. Of the 25.36 miles of lakeshore only 0.85 miles is in public ownership. The Wisconsin Dept. of Natural Resources owns 0.54 miles of this, while the remaining public frontage consists of 34 platted access sites, only three of which are developed. Two of these developed accesses are located southwest of the inlet from Grindstone Creek, and the other is at Victory Heights opposite Musky Bay.

Surface Acres = 5,638.8, Maximum Depth = 90 feet, M.P.A. = 45 ppm, Secchi Disk = 15 feet

Date  1969

Author   Surface Water Inventory Of Wisconsin

Lac Courte Oreilles, Couderay River Watershed (UC20) Fish and Aquatic LifeLac Courte Oreilles, Couderay River Watershed (UC20) RecreationLac Courte Oreilles, Couderay River Watershed (UC20) Fish Consumption

General Condition

Lac Courte Oreilles (2390800) was assessed during the 2016 listing cycle; total phosphorus and chlorophyll sample data were clearly below 2016 WisCALM listing thresholds for the Recreation use and Fish and Aquatic Life use.

Date  2015

Author  Aaron Larson

Impaired Waters

Lac Courte Oreilles (WBIC 2390800) was assessed during the 2018 listing cycle; new dissolved oxygen data clearly exceeded the listing thresholds for the Fish and Aquatic Life Use. Total phosphorus and chlorophyll-a sample data clearly met the Fish and Aquatic Life and Recreation use thresholds. This lake was proposed for listing.

Date  2017

Author  Ashley Beranek


Wisconsin has over 84,000 miles of streams, 15,000 lakes and milllions of acres of wetlands. Assessing the condition of this vast amount of water is challenging. The state's water monitoring program uses a media-based, cross-program approach to analyze water condition. An updated monitoring strategy (2015-2020) is now available. Compliance with Clean Water Act fishable, swimmable standards are located in the Executive Summary of Water Condition in 2018. See also the 'monitoring and projects' tab.



Shoreland Monitoring, Assessment, Inventory
Courte Oreilles Lake Association is sponsoring a project to design and install shoreline buffer restorations on Lac Courte Oreilles and Little Lac Courte Oreilles Lakes. Project tasks include: 1) Shoreline buffer design/restoration on approximately 25 shoreline sites; 2) Modeling to estimate TSS and TP reductions from buffer restorations; 3) Develop and distribute shoreline buffer educational materials.

Management Goals

Wisconsin's Water Quality Standards provide qualitative and quantitative goals for waters that are protective of Fishable, Swimmable conditions [Learn more]. Waters that do not meet water quality standards are considered impaired and restoration actions are planned and carried out until the water is once again fishable and swimmable

Management goals can include creation or implementation of a Total Maximum Daily Load analysis, a Nine Key Element Plan, or other restoration work, education and outreach and more. If specific recommendations exist for this water, they will be displayed below online.


Monitoring the condition of a river, stream, or lake includes gathering physical, chemical, biological, and habitat data. Comprehensive studies often gather all these parameters in great detail, while lighter assessment events will involve sampling physical, chemical and biological data such as macroinvertebrates. Aquatic macroinvertebrates and fish communities integrate watershed or catchment condition, providing great insight into overall ecosystem health. Chemical and habitat parameters tell researchers more about human induced problems including contaminated runoff, point source dischargers, or habitat issues that foster or limit the potential of aquatic communities to thrive in a given area. Wisconsin's Water Monitoring Strategy was recenty updated.

Grants and Management Projects

Monitoring Projects

Watershed Characteristics

Lac Courte Oreilles is located in the Couderay River watershed which is 212.25 miĀ². Land use in the watershed is primarily forest (64.90%), wetland (13.50%) and a mix of open (12.90%) and other uses (8.70%). This watershed has 211.96 stream miles, 18,300.76 lake acres and 14,697.69 wetland acres.

Nonpoint Source Characteristics

This watershed is ranked Low for runoff impacts on streams, High for runoff impacts on lakes and Low for runoff impacts on groundwater and therefore has an overall rank of Low. This value can be used in ranking the watershed or individual waterbodies for grant funding under state and county programs.This water is ranked High Lake for individual Lakes based on runoff problems and the likelihood of success from project implementation.

Natural Community

Lac Courte Oreilles is considered a Two-Story under the state's Natural Community Determinations.

Natural communities (stream and lake natural communities) represent model results and DNR staff valiation processes that confirm or update predicted conditions based on flow and temperature modeling from historic and current landscape features and related variables. Predicated flow and temperatures for waters are associated predicated fish assemblages (communities). Biologists evaluate the model results against current survey data to determine if the modeled results are corect and whether biological indicators show water quaity degradation. This analysis is a core component of the state's resource management framework. Wisconsin's Riverine Natural Communities.

Shallow headwater lake describes the depth and location of the lake in a watershed. These variables affect the lakes response to watershed variables.

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