South Oscar Lake
Douglas County, MinnesotaView mapDirections
Minnesota PCA publishes the water-quality measurements for South Oscar Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Mercury
- 2 aquatic invasives
- 58 ft max depth
- Public access
- Limited data
South Oscar Lake in Douglas County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 16.7 ft visibility. Phosphorus: 20 µg/L. Chlorophyll-a (algae): 2.9 µg/L.
South Oscar Lake is a mesotrophic lake in Douglas County, Minnesota with an estimated average depth of about 58 feet. Limited fish-species data available. Public access is available. Compared to the 36 other monitored lakes in Douglas County, South Oscar Lake ranks #21 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2020-09-01. Methodology: how these readings are compared.
What South Oscar Lake is good for
From access and monitoring records, not editorial picks.
- Clear water16.7 ft of visibility
Swimming conditions
Readings onlyLimited data
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. South Oscar Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether South Oscar 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 South Oscar Lake
These are the measurements Minnesota PCA publishes for South Oscar Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Crystal clear, you can see 16.7 ft down. Phosphorus 20 µg/L. Chlorophyll-a 2.9 µg/L. TSI 42.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 16.7ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 20µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 2.9µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 42 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about South Oscar Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
South Oscar Lake typically sits around 66°F at the surface in September. Summer average is about 72°F. Usually warmest in Jul (about 77°F) and coldest in May (about 53°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (53°F) to its warmest (77°F).
Typical surface water temperature by month, from 40 field readings (2019–2019) via the EPA Water Quality Portal. See the full South Oscar Lake water temperature breakdown →
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for South Oscar Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Aquatic Plant Report — Oscar (0933)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — OscarFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — OscarPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
~58 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 South Oscar Lake.
Lake Size & Watershed
Watershed (drainage) area
10 sq mi
HydroLAKES / HydroSHEDS
Surface area
1,087 acres
HydroLAKES / HydroSHEDS
Shoreline
13.4 mi
HydroLAKES / HydroSHEDS
Elevation
1,375 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.
Stays via Stay22
Stays near South Oscar Lake
Compare lakeside cabins, hotels, and vacation rentals near South Oscar Lake in Douglas 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.
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Fishing South Oscar 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.
EPA Impairment Status
South Oscar 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.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN21-0257-02 · Official waterbody report
Nearby Lakes in Douglas County
Frequently asked questions about South Oscar Lake
Where is South Oscar Lake?
- South Oscar Lake is a lake in Douglas County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of South Oscar Lake?
- South Oscar Lake in Douglas County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 16.7 ft visibility. Phosphorus: 20 µg/L. Chlorophyll-a (algae): 2.9 µg/L.
Is South Oscar Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. South Oscar Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
What is the water temperature of South Oscar Lake?
- South Oscar Lake typically sits around 66°F at the surface in September, from 40 EPA Water Quality Portal field readings (2019–2019). That is a typical value for the month, not a live reading.
How deep is South Oscar Lake?
- No published bathymetric survey covers South Oscar Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 58 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Can I fish at South Oscar Lake?
- Public access to South Oscar 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.
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Where this data comes from
15 measurements from 1 monitoring station, 2020. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA15 samples · 2020
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder