Long Lake
Long Lake in Washington County, Minnesota has a water quality grade of C (Fair). Water clarity: 8 ft visibility. Phosphorus: 25 µg/L. Chlorophyll-a (algae): 5.6 µg/L. Maximum depth: 25 ft. Surface area: 53.12 acres.
- Clarity
- 8 ft
- Max depth
- 25 ft
- Area
- 53 acres
- Type
- Mesotrophic
- Public access
- No
- Ice-out
- Apr 12
- Open water
- 233 days
Next lake in Washington County
Long Lake is a 53-acre mesotrophic lake in Washington County, Minnesota with a maximum depth of 25 feet. Water quality is graded C based on 2 sampling years through 2024. Limited fish-species data available. No public access — the lake is private or restricted. Compared to the 74 other monitored lakes in Washington County, Long Lake ranks #25 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-22. Grade methodology: LakeGrade methodology.
Watch Long Lake water quality
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Swimming Safety
Grade onlyLimited data
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.
Generally safe for swimming, moderate water quality
Water Quality Grade: C (Fair)
Moderate clarity, visible to about 8 ft. Phosphorus level: 25 µg/L. Chlorophyll-a: 5.6 µg/L. Trophic State Index: 48.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 8 ft | Not graded |
| Phosphorus | 25 µg/L | Fair |
| Chlorophyll-a (Algae) | 5.6 µg/L | Good |
| Trophic State Index (TSI) | 48 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Long Lake
Compare lakeside cabins, hotels, and vacation rentals near Long Lake in Washington 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.
Top-rated places to stay near Long Lake
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Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 25 ft |
| Surface Area | 53 acres |
| Shoreline Length | 2.1 mi |
| Littoral Zone | 83% |
| Public Access | No |
Fishing Long 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.
DNR Fisheries Survey Summary
1 survey on file from MN DNR Fisheries. Most recent: 1992-06-17 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Black Bullhead | 155.75 | 0.08 lb |
| Bluegill | 15.00 | 0.14 lb |
| Pumpkinseed | 4.25 | 0.08 lb |
| Hybrid Sunfish | 2.50 | 0.11 lb |
| Black Crappie | 2.50 | 0.16 lb |
| Brown Bullhead | 1.50 | 0.31 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
From the 1992-06-17 survey
BLB ABUNDANCE WAS HIGH. GILLNET AND TRAPNET CATCHES WERE 3 AND 56 TIMES ABOVE THE LOCAL MEDIAN LEVELS RESPECTIVELY. HSF, PMK, BLG, AND BLC WERE SAMPLED AT ABOVE LOCAL MEDIAN ABUNDANCE. BLG PSD WAS 25. BLG AND BLC WERE PROBABLY INTRODUCED SINCE THE 1977 NETTING. NOP, BRB, AND GSF WERE SAMPLED NEAR LOCAL MEDIAN LEVELS.…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Long Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — LongFisheries Lake Survey · MN DNR LakeFinder
Ice Season
Historical ice data from Minnesota DNR (8 observations).
Estimated open water season: 233 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2007-03-28 (2007) | 2008-04-21 (2008) |
| Ice-In | 2007-11-25 (2007) | 2020-12-01 (2020) |
Most recent ice-out: 2022-04-12
EPA Impairment Status
Long 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 MN82-0021-00 · Official waterbody report
County Ranking
Ranked #25 of 75 lakes in Washington County
Nearby Lakes in Washington County
Frequently asked questions about Long Lake
What is the water quality grade for Long Lake?
- Long Lake in Washington County, Minnesota has a water quality grade of C (Fair). Water clarity: 8 ft visibility. Phosphorus: 25 µg/L. Chlorophyll-a (algae): 5.6 µg/L. Maximum depth: 25 ft. Surface area: 53.12 acres.
Is Long Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Long Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 5.6 µg/L. Always check local health department advisories before swimming.
How deep is Long Lake?
- Long Lake has a maximum depth of 25 feet. The lake covers 53.12 acres.
When does Long Lake thaw?
- Long Lake typically has ice-out around Apr 12. Ice typically forms around Dec 1. The open water season is approximately 233 days.
Explore Long Lake across LakeGrade
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Fish species and best lakes in Washington County
Species activity outlook by water temperature and season
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Moderate nutrients, good water quality
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Other Grade C Lakes in Minnesota
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Where this data comes from
117 measurements from 3 monitoring stations, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA117 samples · 2020–2024
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- Analysis of Chlorophyll in Periphyton and Plankton
Monitoring station identifiers (3)
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
Ice data from Minnesota DNR Climate