South Twin Lake
Washington County, MinnesotaView mapDirections
Minnesota PCA publishes the water-quality measurements for South Twin Lake. Here is what has been measured.
- Eutrophic
- 37 ft max depth
- Limited data
South Twin Lake in Washington County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 5 ft visibility. Phosphorus: 32 µg/L. Chlorophyll-a (algae): 9 µg/L.
South Twin Lake is a productive, nutrient-rich eutrophic lake in Washington County, Minnesota with an estimated average depth of about 37 feet. Limited fish-species data available. No public access — the lake is private or restricted. Compared to the 74 other monitored lakes in Washington County, South Twin Lake ranks #32 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-17. Methodology: how these readings are compared.
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. Check local advisories before you swim.
Whether South Twin 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 Twin Lake
These are the measurements Minnesota PCA publishes for South Twin 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 5 ft. Phosphorus 32 µg/L. Chlorophyll-a 9 µg/L. TSI 53.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 32µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 9µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 53 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about South Twin Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
South Twin Lake typically sits around 53°F at the surface in October. Summer average is about 74°F. Usually warmest in Jul (about 77°F) and coldest in Apr (about 49°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (49°F) to its warmest (77°F).
Typical surface water temperature by month, from 90 field readings (2010–2024) via the EPA Water Quality Portal. See the full South Twin Lake water temperature breakdown →
Lake Details
Max depth
~37 ft est.
Public access
No
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 Twin Lake.
Lake Size & Watershed
Watershed (drainage) area
21 sq mi
HydroLAKES / HydroSHEDS
Surface area
44 acres
HydroLAKES / HydroSHEDS
Shoreline
1.1 mi
HydroLAKES / HydroSHEDS
Elevation
886 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 Twin Lake
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Top-rated places to stay near South Twin Lake
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Fishing South Twin Lake
Nearby Lakes in Washington County
Frequently asked questions about South Twin Lake
Where is South Twin Lake?
- South Twin 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 South Twin Lake?
- South Twin Lake in Washington County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 5 ft visibility. Phosphorus: 32 µg/L. Chlorophyll-a (algae): 9 µg/L.
Is South Twin 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 South Twin Lake?
- South Twin Lake typically sits around 53°F at the surface in October, from 90 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
How deep is South Twin Lake?
- No published bathymetric survey covers South Twin Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 37 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 Twin Lake?
- Public access to South Twin Lake is listed as no on the lake record, so confirm before you make the trip. 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 South Twin Lake across LakeQuality
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Where this data comes from
28 measurements from 1 monitoring station, 2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA28 samples · 2024
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- Analysis of Chlorophyll in Periphyton and Plankton
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