Oneka Lake
Washington County, MinnesotaView mapDirections
Minnesota PCA publishes the water-quality measurements for Oneka Lake. Here is what has been measured.
- 30 ft max depth
- Public access
- Limited data
Oneka Lake in Washington County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 4.4 ft visibility.
Oneka Lake is a lake in Washington County, Minnesota with an estimated average depth of about 30 feet. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2023-08-18. Methodology: how these readings are compared.
What Oneka Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Oneka 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 Oneka Lake
These are the measurements Minnesota PCA publishes for Oneka 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 4.4 ft. TSI 56.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 4.4ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 56 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Oneka Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Oneka Lake typically sits around 74°F at the surface in September. Summer average is about 75°F. Usually warmest in Jul (about 82°F) and coldest in May (about 57°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (57°F) to its warmest (82°F).
Typical surface water temperature by month, from 18 field readings (2010–2023) via the EPA Water Quality Portal. See the full Oneka Lake water temperature breakdown →
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Oneka Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Public Water Access Sites — OnekaPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
~30 ft est.
Public access
Yes
Listed by Minnesota PCA
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Minnesota has not published bathymetry for Oneka Lake.
Lake Size & Watershed
Watershed (drainage) area
13 sq mi
HydroLAKES / HydroSHEDS
Surface area
339 acres
HydroLAKES / HydroSHEDS
Shoreline
2.8 mi
HydroLAKES / HydroSHEDS
Elevation
915 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Recreation & Access
- Oneka Lake ParkPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Oneka Lake
Compare lakeside cabins, hotels, and vacation rentals near Oneka Lake in Washington 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.
Top-rated places to stay near Oneka 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 →
Follow Oneka Lake’s readings
Email me when new measurements post for this lake. Updates stay free.
Or email
Fishing Oneka Lake
Water quality readings over time
2 seasons of samples on record (2022–2023). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening2 years
Nearby Lakes in Washington County
Frequently asked questions about Oneka Lake
Where is Oneka Lake?
- Oneka Lake is a lake in Washington County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Oneka Lake?
- Oneka Lake in Washington County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 4.4 ft visibility.
Is Oneka Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Oneka Lake?
- Oneka Lake typically sits around 74°F at the surface in September, from 18 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
How deep is Oneka Lake?
- No published bathymetric survey covers Oneka Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 30 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Are there boat ramps on Oneka Lake?
- Oneka Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Oneka Lake Park. Public access is listed as yes.
Can I fish at Oneka Lake?
- Oneka 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 Minnesota's fish and wildlife agency, so check its current regulations before you go.
Explore Oneka Lake across LakeQuality
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in Washington County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
Lakes in the St. Croix Watershed, ranked by water quality
Minnesota's cleanest lakes, ranked on agency measurements
More lakes in Minnesota
State Parks Near Oneka Lake
Other Lakes in Minnesota
Eutrophic Lakes in Minnesota
Where this data comes from
8 measurements from 1 monitoring station, 2022–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA8 samples · 2022–2023
Analytical methods
- Field measurement/observation, generic method
Monitoring station identifiers (1)
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory