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LakeQuality

Lac Courte Oreilles Lake

Sawyer County, Wisconsin5,139 acresView mapDirections

Wisconsin DNR publishes the water-quality measurements for Lac Courte Oreilles Lake. Here is what has been measured.

Clarity
12.2 ft
Clearer than most
Secchi · sampled 2026
Phosphorus
15 µg/L
Typical for Wisconsin
Measured by Wisconsin DNR
Chlorophyll-a
1.7 µg/L
Typical for Wisconsin
Measured by Wisconsin DNR
Water temp
~70°F
Typical for Sep · EPA WQP
Max depth
90 ft
Bathymetric survey
Area
5,139 acres
Surface area
  • Mesotrophic
  • Impaired · Cause unknown
  • 2 aquatic invasives
  • 90 ft max depth
  • Public access
See the measurementsDirectionsWhere to stay

Lac Courte Oreilles Lake in Sawyer County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 12.2 ft visibility. Phosphorus: 15 µg/L. Chlorophyll-a (algae): 1.7 µg/L. Maximum depth: 90 ft. Surface area: 5139 acres.

Wisconsin DNR rates Northern Pike as abundant on Lac Courte Oreilles Lake. DNR survey details →

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Lac Courte Oreilles Lake is a 5,139-acre mesotrophic lake in Sawyer County, Wisconsin with a maximum depth of 90 feet. Overall water quality is improving over recent sampling years. The lake supports 6 documented fish species including Musky, Panfish, and Largemouth Bass. Public access is available with 1 public boat landing. Compared to the 44 other monitored lakes in Sawyer County, Lac Courte Oreilles Lake ranks #1 for water quality.

Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-04-29. Methodology: how these readings are compared.

At about 5,100 acres, Lac Courte Oreilles Lake is large enough that where you stay decides which shore you see most of. It has one public boat landing. Vrbo is where to look for cabins and lake homes around Lac Courte Oreilles Lake, and Booking.com and Expedia search hotels near the lake for your dates.

What Lac Courte Oreilles Lake is good for

From access and monitoring records, not editorial picks.

  • Clear water12.2 ft of visibility
  • Boat launch1 documented ramp
  • Fishing6 species recorded
  • Deep water90 ft surveyed max depth
  • Big water5,139 acres

Swimming conditions

Readings only

Low algae

Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.

Nutrient and algae readings are not a swimming clearance. Lac Courte Oreilles Lake is listed impaired under Clean Water Act §303(d) (IR 5) for cause unknown. Check local advisories before you swim.

Whether Lac Courte Oreilles Lake is safe to swim in today is a call for the Wisconsin Department of Natural Resources and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.

Compare swimming lakes near Hayward →

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Water quality measurements for Lac Courte Oreilles Lake

These are the measurements Wisconsin DNR publishes for Lac Courte Oreilles Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.

Good clarity, visible to about 12.2 ft. Phosphorus 15 µg/L. Chlorophyll-a 1.7 µg/L. TSI 40.

Water quality readings
MeasureReadingWhere it sits
Water clarity (Secchi depth)12.2ftMeasured, not scored

How deep a black-and-white disk stays visible from the surface. Higher is clearer.

Total phosphorus15µg/LGood
GoodFairPoor
Chlorophyll-a (algae)1.7µg/LGood
GoodFairPoor
Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a.40Mesotrophic
OligotrophicMesotrophicEutrophicHypereutrophic

Moderate nutrients, good water quality

Ask about Lac Courte Oreilles Lake

Answers come straight from the public measurements and survey records on this page.

Water Temperature

Lac Courte Oreilles Lake typically sits around 70°F at the surface in September. Summer average is about 72°F. Usually warmest in Aug (about 73°F) and coldest in Sep (about 70°F). These are typical values by month — not a live reading.

Jan
Feb
Mar
Apr
May
Jun
71°
Jul
73°
Aug
70°
Sep
Oct
Nov
Dec

Column height runs from this lake’s coldest month (70°F) to its warmest (73°F).

Typical surface water temperature by month, from 17 field readings (2024–2024) via the EPA Water Quality Portal. See the full Lac Courte Oreilles Lake water temperature breakdown →

Blue-Green Algae (Cyanobacteria)

No current satellite reading

There’s no recent EPA CyAN cyanobacteria estimate for Lac Courte Oreilles Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was high (114,815 cells/mL) on December 14, 2024.

Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗

DNR fisheries survey

Wisconsin DNR rates Northern Pike as abundant on Lac Courte Oreilles Lake.

A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Lac Courte Oreilles Lake’s water-quality measurements separately, and the water-quality trend over 5 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.

WI DNR Lake Profile

Authoritative data from the Wisconsin DNR LakePages. 36 stations on file (most recent sample 2025).

DNR Assessment
Reported
Trophic State Index 39 (oligotrophic) · 5-year average

Fish Species (DNR-rated)

Northern Pike(Abundant)Musky(Common)Panfish(Common)Smallmouth Bass(Common)Walleye(Common)Largemouth Bass(Present)
Contour map (PDF) →Full WI DNR LakePage →Water quality stations →

DNR Reports & Resources

Wisconsin DNR Fisheries scientists publish multi-year survey reports for Lac Courte Oreilles Lake covering fish populations, stocking, water quality, and management. 2 reports on file.

These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).

Lake Details

Max depth

90 ft

Surface area

5,139 acres

Public access

Yes

Listed by Wisconsin DNR

Recreation & Access

1
Boat Landings
Yes
Public Access
  • Lac Courte OreillesPublic

Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps

Stays via Stay22

Stays near Lac Courte Oreilles Lake

Compare lakeside cabins, hotels, and vacation rentals near Lac Courte Oreilles Lake in Sawyer County, Wisconsin — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.

Top-rated places to stay near Lac Courte Oreilles Lake

Prices for Oct 9–11, 4 adults. Change dates on the map below.

Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.

Planning a trip? Cabins and lodging at Lac Courte Oreilles Lake → · more Wisconsin lake trips

Follow Lac Courte Oreilles Lake’s readings

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Fish Species

MuskyPanfishLargemouth BassSmallmouth BassNorthern PikeWalleye

Click a species to see every lake where it is documented.

Fishing Lac Courte Oreilles Lake

Invasive & Introduced Species

Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.

Banded Mystery SnailChinese Mystery SnailCurly-Leaf PondweedEurasian Water-MilfoilRusty Crayfish

Water Quality Trend: Improving

Based on 5 years of monitoring (2020–2024).

  • Water clarity

    Improving

    5 years

  • Phosphorus

    Improving

    -1.15 µg/L/yr4 years

  • Chlorophyll-a

    Improving

    -0.21 µg/L/yr4 years

See year-by-year chart →

EPA Impairment Status

Lac Courte Oreilles Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).

Causes of impairment

Cause unknown

Designated uses not supporting: Aquatic life.

Source: EPA ATTAINS assessment unit WI10004082 · Official waterbody report

Nearby Lakes in Sawyer County

Johnson Lake—View →Durphee Lake8.1 ft clear · Mesotrophic—View →
Whitefish Lake13.5 ft clear · OligotrophicCompare—View →
Minnemac Lake—View →Lake Twenty-seven—View →Little Lac Courte Lake12.3 ft clear—View →

Frequently asked questions about Lac Courte Oreilles Lake

Where is Lac Courte Oreilles Lake?

Lac Courte Oreilles Lake is a lake in Sawyer County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.

What is the water quality of Lac Courte Oreilles Lake?

Lac Courte Oreilles Lake in Sawyer County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 12.2 ft visibility. Phosphorus: 15 µg/L. Chlorophyll-a (algae): 1.7 µg/L. Maximum depth: 90 ft. Surface area: 5139 acres.

Measurements on this page ↑

Is Lac Courte Oreilles Lake safe to swim in?

Nutrient and algae readings are not a swimming clearance. Lac Courte Oreilles Lake is listed impaired under Clean Water Act §303(d) (IR 5) for cause unknown. Check local advisories before you swim.

Swimming on this page ↑

What is the water temperature of Lac Courte Oreilles Lake?

Lac Courte Oreilles Lake typically sits around 70°F at the surface in September, from 17 EPA Water Quality Portal field readings (2024–2024). That is a typical value for the month, not a live reading.

Temp on this page ↑

How deep is Lac Courte Oreilles Lake?

Lac Courte Oreilles Lake has a maximum depth of 90 feet. The lake covers 5139 acres.

What fish are in Lac Courte Oreilles Lake?

Fish species found in Lac Courte Oreilles Lake include Musky, Panfish, Largemouth Bass, Smallmouth Bass, Northern Pike, Walleye. Lac Courte Oreilles Lake is located in Sawyer County, Wisconsin.

Fish on this page ↑

What did the DNR fisheries survey find at Lac Courte Oreilles Lake?

Wisconsin DNR rates Northern Pike as abundant on Lac Courte Oreilles Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Lac Courte Oreilles Lake’s water-quality measurements separately, and the water-quality trend over 5 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.

DNR on this page ↑

Does Lac Courte Oreilles Lake have blue-green algae?

There is no recent EPA CyAN cyanobacteria estimate for Lac Courte Oreilles Lake (clouds, ice, or an off-season gap). The most recent reading was high (114,815 cells/mL). Blue-green algae can appear and clear within days, so check Wisconsin's current advisory before swimming.

Algae on this page ↑

Are there boat ramps on Lac Courte Oreilles Lake?

Lac Courte Oreilles Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Lac Courte Oreilles. Public access is listed as yes.

Access on this page ↑

Can I fish at Lac Courte Oreilles Lake?

Lac Courte Oreilles Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Wisconsin's fish and wildlife agency, so check its current regulations before you go.

Access on this page ↑

Explore Lac Courte Oreilles Lake across LakeQuality

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Compare Lac Courte Oreilles Lake With Nearby Lakes

Lac Courte Oreilles Lake vs Chippewa Flowage -North of Cranberry Bars Lake

Sawyer County · 4.9 ft

Lac Courte Oreilles Lake vs Whitefish Lake

Sawyer County · 13.5 ft

Lac Courte Oreilles Lake vs Round Lake

Sawyer County · 21.1 ft

Lac Courte Oreilles Lake vs Grindstone Lake

Sawyer County · 17.4 ft

Lac Courte Oreilles Lake vs Nelson Lake

Sawyer County · 5 ft

Lac Courte Oreilles Lake vs Lake Chetac

Sawyer County

Where this data comes from

1,759 measurements from 20 monitoring stations, 2020–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.

Collected and reported by

  • Lac Courte Oreilles (Tribal)LCOWIS_WQX1,158 samples · 2020–2024
  • Wisconsin Department of Natural ResourcesWIDNR_WQX601 samples · 2020–2026

Analytical methods

  • 4500 P E ~ Phosphorus in Water by Colorimetry- Ascorbic Acid Method
  • 4500 P F ~ Phosphorus in Water by Colorimetry Automated Ascorbic Acid Method
  • 4500 P E ~ Phosphorus by Ascorbic Acid
  • 10200 H ~ Chlorophyll a-b-c Determination
  • Phosphorus by Colorimetry
Monitoring station identifiers (20)

EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.

Other records on this page

Impairment status from EPA ATTAINS 303(d) database

Fish and recreation data from Wisconsin DNR Lakes

Named boat-access points from the USGS National Boat Ramps inventory