South Oscar Lake
South Oscar Lake in Douglas County, Minnesota has a water quality grade of A (Excellent). Water clarity: 16.7 ft visibility. Phosphorus: 20 µg/L. Chlorophyll-a (algae): 2.9 µg/L.
- Clarity
- 16.7 ft
- Typical in August
- 74°F
- Mean depth
- ~17 ft est.
- Type
- Mesotrophic
- Public access
- Yes
Next lake in Douglas County
South Oscar Lake is a mesotrophic lake in Douglas County, Minnesota with an estimated average depth of about 17 feet. Water quality is graded A based on 2 sampling years through 2020. Limited fish-species data available. Public access is available with 1 public boat landing. 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. 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.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
Crystal clear, you can see 16.7 ft down. Phosphorus level: 20 µg/L. Chlorophyll-a: 2.9 µg/L. Trophic State Index: 42.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 16.7 ft | Not graded |
| Phosphorus | 20 µg/L | Good |
| Chlorophyll-a (Algae) | 2.9 µg/L | Good |
| Trophic State Index (TSI) | 42 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay 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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Water Temperature
South Oscar Lake typically sits around 74°F at the surface in August. 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.
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 →
Lake Details
| Characteristic | Value |
|---|---|
| Average Depth | ~17 ft est. |
| Public Access | Yes |
Depth marked “est.” is a modeled estimate from HydroLAKES, not a measured survey. Minnesota has not published bathymetry for South Oscar Lake.
Lake Size & Watershed
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
- Oscar LakePublic
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.
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
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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN21-0257-02 · Official waterbody report
County Ranking
Ranked #21 of 37 lakes in Douglas County
Nearby Lakes in Douglas County
Frequently asked questions about South Oscar Lake
What is the water quality grade for South Oscar Lake?
- South Oscar Lake in Douglas County, Minnesota has a water quality grade of A (Excellent). 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?
- Excellent for swimming, crystal clear water with minimal algae. South Oscar Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 2.9 µg/L. Always check local health department advisories before swimming.
What is the water temperature of South Oscar Lake?
- South Oscar Lake typically sits around 74°F at the surface in August, 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 17 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 South Oscar Lake?
- South Oscar Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Oscar Lake. Public access is listed as yes.
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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)
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory