Lost Lake
Lost Lake in Hennepin County, Minnesota has a water quality grade of A (Excellent). 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.
- Clarity
- 3.2 ft
- Typical in August
- 75°F
- Max depth
- 6 ft
- Area
- 23 acres
- Type
- Eutrophic
- Trend
- ↓ Declining
- Public access
- Yes
- Ice-out
- Apr 2
- Open water
- 237 days
Next lake in Hennepin County
Lost Lake is a 23-acre productive, nutrient-rich eutrophic lake in Hennepin County, Minnesota with a maximum depth of 6 feet. Water quality is graded A based on 1 sampling years through 2025. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. 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. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLow algae
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)
Very murky, less than 3.2 ft of visibility. Phosphorus level: 86 µg/L. Chlorophyll-a: 5.8 µg/L. Trophic State Index: 59.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.2 ft | Not graded |
| Phosphorus | 86 µg/L | Not graded |
| Chlorophyll-a (Algae) | 5.8 µg/L | Good |
| Trophic State Index (TSI) | 59 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Lost Lake
Compare lakeside cabins, hotels, and vacation rentals near Lost Lake in Hennepin 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
Lost Lake typically sits around 75°F at the surface in August. 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.
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 →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 6 ft |
| Surface Area | 23 acres |
| Shoreline Length | 0.8 mi |
| Littoral Zone | 100% |
| Public Access | Yes |
Recreation & Access
- French Regional ParkPublic
Fishing Lost Lake
DNR Fisheries Survey Summary
1 survey on file from MN DNR Fisheries. Most recent: 1979-08-08 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Hybrid Sunfish | 0.33 | 0.3 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
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
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.119 m/yr | 6 |
| Phosphorus | ↓ Declining | +22.89 µg/L/yr | 4 |
| Chlorophyll-a | ↓ Declining | +8.59 µg/L/yr | 4 |
Ice Season
Historical ice data from Minnesota DNR (8 observations).
Estimated open water season: 237 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2017-03-07 (2017) | 2008-04-18 (2008) |
| Ice-In | 2023-11-16 (2023) | 2021-12-21 (2021) |
Most recent ice-out: 2022-04-08
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
Source: EPA ATTAINS assessment unit MN27-0103-00 · Official waterbody report
County Ranking
Ranked #5 of 81 lakes in Hennepin County
Nearby Lakes in Hennepin County
Frequently asked questions about Lost Lake
What is the water quality grade for Lost Lake?
- Lost Lake in Hennepin County, Minnesota has a water quality grade of A (Excellent). 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?
- Excellent for swimming, crystal clear water with minimal algae. Lost Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 5.8 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Lost Lake?
- Lost Lake typically sits around 75°F at the surface in August, 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.
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.
Are there boat ramps on Lost Lake?
- Lost Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include French Regional Park. Public access is listed as yes.
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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)
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 details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate