Oak Lake
Carver County, Minnesota333 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Oak Lake. Here is what has been measured.
- Eutrophic
- Impaired · Mercury
- Eurasian watermilfoil
- 11 ft max depth
- Public access
- Limited data
Oak Lake in Carver County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 4.5 ft visibility. Phosphorus: 42.5 µg/L. Chlorophyll-a (algae): 17.5 µg/L. Maximum depth: 11 ft. Surface area: 333.17 acres.
Minnesota DNR's Standard Survey on August 15, 2011 caught 7.33 walleye per gill net at Oak Lake. Length samples in the latest survey that recorded them ran 12–27 inches. DNR survey details →
Oak Lake is a 333-acre productive, nutrient-rich eutrophic lake in Carver County, Minnesota with a maximum depth of 11 feet. The lake supports 12 documented fish species including black bullhead, black crappie, and bluegill. Public access is available. Compared to the 37 other monitored lakes in Carver County, Oak Lake ranks #11 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2021-10-06. Methodology: how these readings are compared.
What Oak Lake is good for
From access and monitoring records, not editorial picks.
- Fishing12 species recorded
- Ice seasonIce-out around Mar 29
Swimming conditions
Readings onlyRecreation use not supported
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. Oak Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Oak Lake is safe to swim in today is a call for the Minnesota Pollution Control Agency and the Minnesota DNR and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Oak Lake
These are the measurements Minnesota PCA publishes for Oak Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 4.5 ft. Phosphorus 42.5 µg/L. Chlorophyll-a 17.5 µg/L. TSI 57.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 4.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 42.5µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 17.5µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 57 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Oak Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Oak Lake typically sits around 67°F at the surface in October. Summer average is about 76°F. Usually warmest in Jun (about 78°F) and coldest in Oct (about 67°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (67°F) to its warmest (78°F).
Typical surface water temperature by month, from 48 field readings (2021–2021) via the EPA Water Quality Portal. See the full Oak Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Oak Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was very high (1,202,264 cells/mL) on September 20, 2025.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Minnesota DNR's Standard Survey on August 15, 2011 caught 7.33 walleye per gill net at Oak Lake. Length samples in the latest survey that recorded them ran 12–27 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Oak Lake’s water-quality measurements separately. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
3 surveys on file from MN DNR Fisheries. Most recent: 2011-08-15 (Standard Survey).
3 surveys on file · most recent 2011-08-15 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Black Bullhead | 99.05 | 1–10 in 2011-08-15 | 0.3 lb |
| Black Crappie | 27.18 | 4–10 in 2011-08-15 | 0.2 lb |
| Bluegill | 25.81 | 2–8 in 2011-08-15 | 0.16 lb |
| Walleye | 7.42 | 12–27 in 2011-08-15 | 2.33 lb |
| Pumpkinseed | 5.67 | 1–7 in 1995-08-14 | 0.19 lb |
| Common Carp | 3.39 | 11–30 in 2011-08-15 | 3.61 lb |
CPUE = catch per unit effort, fish caught per net per set in a standardised survey. It measures abundance, not size, and is not a weekly bite report.
Length Distributions
Number of fish caught at each inch class in the most recent survey that recorded lengths. Red dashed line marks an approximate trophy threshold for that species.
Black Bullhead
Black Crappie
Bluegill
Walleye
From the 2011-08-15 survey
Oak is a shallow, eutrophic, 339-acre lake located in northern Carver County near the city of Watertown. It is primarily managed for northern pike and secondarily largemouth bass and bluegill. The lake is occasionally stocked with walleye by a landowner who lives on the lake (with a permit from the DNR). Oak lake is…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Oak Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — OakFisheries Lake Survey · MN DNR LakeFinder
Lake Details
Max depth
11 ft
Surface area
333 acres
Shoreline
7 mi
Littoral zone
100%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
3 sq mi
HydroLAKES / HydroSHEDS
Elevation
948 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Stays via Stay22
Stays near Oak Lake
Compare lakeside cabins, hotels, and vacation rentals near Oak Lake in Carver County, Minnesota — 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. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Oak Lake are listed below.
Top-rated places to stay near Oak 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 whole trip? See where to stay at Minnesota’s top lakes →
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Fish Species
Click a species to see every lake where it is documented.
Fishing Oak 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.
Ice season
Typical ice-out
Mar 29
Earliest Mar 3, 2024 · Latest Apr 28, 2002
Typical ice-in
Dec 7
Earliest Nov 20, 2003 · Latest Dec 12, 2001
Most recent ice-out
Mar 3
2024
10 observations · Minnesota PCA ice records
EPA Impairment Status
Oak Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Fish consumption, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN10-0093-00 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Oak Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Watertown WwtpWatertown · 2.2 mi away · NPDES MN0020940Recent violation
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Nearby Lakes in Carver County
Frequently asked questions about Oak Lake
Where is Oak Lake?
- Oak Lake is a lake in Carver County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Oak Lake?
- Oak Lake in Carver County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 4.5 ft visibility. Phosphorus: 42.5 µg/L. Chlorophyll-a (algae): 17.5 µg/L. Maximum depth: 11 ft. Surface area: 333.17 acres.
Is Oak Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Oak Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Oak Lake?
- Oak Lake typically sits around 67°F at the surface in October, from 48 EPA Water Quality Portal field readings (2021–2021). That is a typical value for the month, not a live reading.
How deep is Oak Lake?
- Oak Lake has a maximum depth of 11 feet. The lake covers 333.17 acres.
What fish are in Oak Lake?
- Fish species found in Oak Lake include black bullhead, black crappie, bluegill, brown bullhead, common carp, hybrid sunfish, largemouth bass, northern pike, walleye, white crappie, yellow bullhead, yellow perch. Oak Lake is located in Carver County, Minnesota.
What did the DNR fisheries survey find at Oak Lake?
- Minnesota DNR's Standard Survey on August 15, 2011 caught 7.33 walleye per gill net at Oak Lake. Length samples in the latest survey that recorded them ran 12–27 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Oak Lake’s water-quality measurements separately. Catch rate is not a swim clearance and is not a weekly bite report.
When does Oak Lake thaw?
- Oak Lake typically has ice-out around Mar 29. Ice typically forms around Dec 7. The open water season is approximately 253 days.
Does Oak Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Oak Lake (clouds, ice, or an off-season gap). The most recent reading was very high (1,202,264 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Can I fish at Oak Lake?
- Public access to Oak Lake is listed as yes on the lake record. Seasons, size and bag limits, and whether you need a license are set by Minnesota's fish and wildlife agency, so check its current regulations before you go.
Explore Oak Lake across LakeQuality
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Where this data comes from
36 measurements from 2 monitoring stations, 2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA36 samples · 2021
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (2)
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate