Oak Lake
Oak Lake in Carver County, Minnesota has a water quality grade of D (Nutrient-rich). 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.
- Clarity
- 4.5 ft
- Typical in August
- 75°F
- Max depth
- 11 ft
- Area
- 333 acres
- Type
- Eutrophic
- Public access
- Yes
- Ice-out
- Mar 29
- Open water
- 253 days
Grade D measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Oak Lake →
Next lake in Carver County
Oak Lake is a 333-acre productive, nutrient-rich eutrophic lake in Carver County, Minnesota with a maximum depth of 11 feet. Water quality is graded D based on 2 sampling years through 2021. The lake supports 12 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing. 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. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum
Water Quality Grade: D (Nutrient-rich)
Murky, only visible to about 4.5 ft. Phosphorus level: 42.5 µg/L. Chlorophyll-a: 17.5 µg/L. Trophic State Index: 57.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.5 ft | Not graded |
| Phosphorus | 42.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 17.5 µg/L | Poor |
| Trophic State Index (TSI) | 57 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay 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 grade measures nutrients and algae, not lodging — cabins and rentals around Oak Lake are listed below.
Top-rated places to stay near Oak Lake
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 →
Water Temperature
Oak Lake typically sits around 75°F at the surface in August. 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.
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 ↗
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 11 ft |
| Surface Area | 333 acres |
| Shoreline Length | 7 mi |
| Littoral Zone | 100% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Rick Johnson ParkPublic
Fish Species
Click a species to see every graded 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.
DNR Fisheries Survey Summary
3 surveys on file from MN DNR Fisheries. Most recent: 2011-08-15 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Black Bullhead | 99.05 | 0.3 lb |
| Black Crappie | 27.18 | 0.2 lb |
| Bluegill | 25.81 | 0.16 lb |
| Walleye | 7.42 | 2.33 lb |
| Pumpkinseed | 5.67 | 0.19 lb |
| Common Carp | 3.39 | 3.61 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
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
Ice Season
Historical ice data from Minnesota DNR (10 observations).
Estimated open water season: 253 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-03-03 (2024) | 2002-04-28 (2002) |
| Ice-In | 2003-11-20 (2003) | 2001-12-12 (2001) |
Most recent ice-out: 2024-03-03
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
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.
County Ranking
Ranked #11 of 38 lakes in Carver County
Nearby Lakes With Higher Grades
Oak Lake holds Grade D. 2 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
Nearby Lakes in Carver County
Frequently asked questions about Oak Lake
What is the water quality grade for Oak Lake?
- Oak Lake in Carver County, Minnesota has a water quality grade of D (Nutrient-rich). 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?
- Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum. Oak Lake has a water quality grade of D (Nutrient-rich). Algae concentration (chlorophyll-a) is 17.5 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Oak Lake?
- Oak Lake typically sits around 75°F at the surface in August, 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.
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.
Are there boat ramps on Oak Lake?
- Oak Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Rick Johnson Park. Public access is listed as yes.
Explore Oak Lake across LakeGrade
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High nutrients, frequent algae, reduced clarity
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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)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated 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
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate