Olson Lake
Washington County, Minnesota87 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Olson Lake. Here is what has been measured.
- Mesotrophic
- 2 aquatic invasives
- 15 ft max depth
- Limited data
Olson Lake in Washington County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 11.2 ft visibility. Phosphorus: 15 µg/L. Chlorophyll-a (algae): 2.6 µg/L. Maximum depth: 15 ft. Surface area: 87.13 acres.
Olson Lake is a 87-acre mesotrophic lake in Washington County, Minnesota with a maximum depth of 15 feet. Overall water quality is improving over recent sampling years. The lake supports 11 documented fish species including black bullhead, black crappie, and bluegill. No public access — the lake is private or restricted. Compared to the 74 other monitored lakes in Washington County, Olson Lake ranks #12 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-08. Methodology: how these readings are compared.
What Olson Lake is good for
From access and monitoring records, not editorial picks.
- Clear water11.2 ft of visibility
- Fishing11 species recorded
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 Olson 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 Olson Lake
These are the measurements Minnesota PCA publishes for Olson Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 11.2 ft. Phosphorus 15 µg/L. Chlorophyll-a 2.6 µg/L. TSI 42.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 11.2ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 15µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 2.6µg/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 Olson Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Olson Lake typically sits around 60°F at the surface in October. Summer average is about 75°F. Usually warmest in Jul (about 80°F) and coldest in May (about 55°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (55°F) to its warmest (80°F).
Typical surface water temperature by month, from 83 field readings (2011–2024) via the EPA Water Quality Portal. See the full Olson Lake water temperature breakdown →
Lake Details
Max depth
15 ft
Surface area
87 acres
Shoreline
1.9 mi
Littoral zone
100%
Share shallower than 15 ft
Public access
No
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
7 sq mi
HydroLAKES / HydroSHEDS
Elevation
925 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Stays via Stay22
Stays near Olson Lake
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Fish Species
Click a species to see every lake where it is documented.
Fishing Olson 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.
Water quality readings over time
3 seasons of samples on record (2023–2025). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Improving3 years
Nearby Lakes in Washington County
Frequently asked questions about Olson Lake
Where is Olson Lake?
- Olson 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 Olson Lake?
- Olson Lake in Washington County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 11.2 ft visibility. Phosphorus: 15 µg/L. Chlorophyll-a (algae): 2.6 µg/L. Maximum depth: 15 ft. Surface area: 87.13 acres.
Is Olson 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 Olson Lake?
- Olson Lake typically sits around 60°F at the surface in October, from 83 EPA Water Quality Portal field readings (2011–2024). That is a typical value for the month, not a live reading.
How deep is Olson Lake?
- Olson Lake has a maximum depth of 15 feet. The lake covers 87.13 acres.
What fish are in Olson Lake?
- Fish species found in Olson Lake include black bullhead, black crappie, bluegill, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, yellow bullhead, yellow perch. Olson Lake is located in Washington County, Minnesota.
Can I fish at Olson Lake?
- Public access to Olson 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 Olson Lake across LakeQuality
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Where this data comes from
43 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
MNPCA43 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