Lost Lake
Washington County, Minnesota63 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Lost Lake. Here is what has been measured.
- Mesotrophic
- 2 aquatic invasives
- 34 ft max depth
- Limited data
Lost Lake in Washington County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 6.3 ft visibility. Phosphorus: 25 µg/L. Chlorophyll-a (algae): 4.5 µg/L. Maximum depth: 34 ft. Surface area: 63.15 acres.
Lost Lake is a 63-acre mesotrophic lake in Washington County, Minnesota with a maximum depth of 34 feet. Overall water quality is declining 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, Lost Lake ranks #31 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-21. Methodology: how these readings are compared.
What Lost Lake is good for
From access and monitoring records, not editorial picks.
- Fishing11 species recorded
- Deep water34 ft surveyed max depth
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 Lost 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 Lost Lake
These are the measurements Minnesota PCA publishes for Lost 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 6.3 ft. Phosphorus 25 µg/L. Chlorophyll-a 4.5 µg/L. TSI 49.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 6.3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 25µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 4.5µg/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. | 49 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Lost Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Lost Lake typically sits around 57°F at the surface in October. Summer average is about 73°F. Usually warmest in Jul (about 74°F) and coldest in Apr (about 56°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (56°F) to its warmest (74°F).
Typical surface water temperature by month, from 30 field readings (2010–2024) via the EPA Water Quality Portal. See the full Lost Lake water temperature breakdown →
Lake Details
Max depth
34 ft
Surface area
63 acres
Shoreline
1.6 mi
Littoral zone
42%
Share shallower than 15 ft
Public access
No
Listed by Minnesota PCA
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Fish Species
Click a species to see every lake where it is documented.
Fishing Lost 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 Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Phosphorus
Worsening+1.47 µg/L/yr6 years
Chlorophyll-a
Worsening+0.51 µg/L/yr6 years
Nearby Lakes in Washington County
Frequently asked questions about Lost Lake
Where is Lost Lake?
- Lost 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 Lost Lake?
- Lost Lake in Washington County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 6.3 ft visibility. Phosphorus: 25 µg/L. Chlorophyll-a (algae): 4.5 µg/L. Maximum depth: 34 ft. Surface area: 63.15 acres.
Is Lost 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 Lost Lake?
- Lost Lake typically sits around 57°F at the surface in October, from 30 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
How deep is Lost Lake?
- Lost Lake has a maximum depth of 34 feet. The lake covers 63.15 acres.
What fish are in Lost Lake?
- Fish species found in Lost Lake include black bullhead, black crappie, bluegill, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, white sucker, yellow bullhead, yellow perch. Lost Lake is located in Washington County, Minnesota.
Can I fish at Lost Lake?
- Public access to Lost 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 Lost Lake across LakeQuality
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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
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Minnesota's cleanest lakes, ranked on agency measurements
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Where this data comes from
112 measurements from 2 monitoring stations, 2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA112 samples · 2024
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- Analysis of Chlorophyll in Periphyton and Plankton
Monitoring station identifiers (2)
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 details from Minnesota DNR LakeFinder