Lost Lake
Hennepin County, Minnesota23 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Lost Lake. Here is what has been measured.
- Eutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- 6 ft max depth
- Public access
Lost Lake in Hennepin County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3.2 ft visibility. Phosphorus: 86 µg/L. Chlorophyll-a (algae): 5.8 µg/L. Maximum depth: 6 ft. Surface area: 22.98 acres.
Minnesota DNR's Standard Survey on August 8, 1979 caught 0.33 hybrid sunfish per trap net at Lost Lake. DNR survey details →
Lost Lake is a 23-acre productive, nutrient-rich eutrophic lake in Hennepin County, Minnesota with a maximum depth of 6 feet. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available. Compared to the 80 other monitored lakes in Hennepin County, Lost Lake ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-28. Methodology: how these readings are compared.
What Lost Lake is good for
From access and monitoring records, not editorial picks.
- Ice seasonIce-out around Apr 2
Swimming conditions
Readings onlyRecreation use not supported
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. Lost Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). 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.
Very murky, less than 3.2 ft of visibility. Phosphorus 86 µg/L. Chlorophyll-a 5.8 µg/L. TSI 59.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3.2ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 86µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 5.8µg/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. | 59 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Lost Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Lost Lake typically sits around 56°F at the surface in October. Summer average is about 76°F. Usually warmest in Jul (about 79°F) and coldest in Apr (about 48°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (48°F) to its warmest (79°F).
Typical surface water temperature by month, from 58 field readings (2017–2025) via the EPA Water Quality Portal. See the full Lost Lake water temperature breakdown →
Minnesota DNR's Standard Survey on August 8, 1979 caught 0.33 hybrid sunfish per trap net at Lost Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Lost Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
1 survey on file from MN DNR Fisheries. Most recent: 1979-08-08 (Standard Survey).
1 survey on file · most recent 1979-08-08 (Standard Survey)
47 years old| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Hybrid Sunfish | 0.33 | 0.3 lb |
CPUE = catch per unit effort, fish caught per net per set in a standardised survey. It measures abundance, not size, and is not a weekly bite report.
From the 1979-08-08 survey
Only one hybrid Sunfish was taken in three trap nets.
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Lost Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — LostFisheries Lake Survey · MN DNR LakeFinder
Lake Details
Max depth
6 ft
Surface area
23 acres
Shoreline
0.8 mi
Littoral zone
100%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
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Stays near Lost Lake
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Fishing Lost Lake
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Phosphorus
Worsening+22.89 µg/L/yr4 years
Chlorophyll-a
Worsening+8.59 µg/L/yr4 years
Ice season
Typical ice-out
Apr 2
Earliest Mar 7, 2017 · Latest Apr 18, 2008
Typical ice-in
Nov 25
Earliest Nov 16, 2023 · Latest Dec 21, 2021
Most recent ice-out
Apr 8
2022
8 observations · Minnesota PCA ice records
EPA Impairment Status
Lost Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Recreation.
Source: EPA ATTAINS assessment unit MN27-0103-00 · Official waterbody report
Nearby Lakes in Hennepin County
Frequently asked questions about Lost Lake
Where is Lost Lake?
- Lost Lake is a lake in Hennepin 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 Hennepin County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3.2 ft visibility. Phosphorus: 86 µg/L. Chlorophyll-a (algae): 5.8 µg/L. Maximum depth: 6 ft. Surface area: 22.98 acres.
Is Lost Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Lost Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Lost Lake?
- Lost Lake typically sits around 56°F at the surface in October, from 58 EPA Water Quality Portal field readings (2017–2025). That is a typical value for the month, not a live reading.
How deep is Lost Lake?
- Lost Lake has a maximum depth of 6 feet. The lake covers 22.98 acres.
What did the DNR fisheries survey find at Lost Lake?
- Minnesota DNR's Standard Survey on August 8, 1979 caught 0.33 hybrid sunfish per trap net at Lost Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Lost Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
When does Lost Lake thaw?
- Lost Lake typically has ice-out around Apr 2. Ice typically forms around Nov 25. The open water season is approximately 237 days.
Can I fish at Lost Lake?
- Public access to Lost 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.
Explore Lost Lake across LakeQuality
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Where this data comes from
85 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA85 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- Phosphorus by Colorimetry
- Analysis of Chlorophyll in Periphyton and Plankton
- 10200 H ~ Chlorophyll a-b-c Determination
- Turbidity, Nephelometric Method
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 details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate