Long Lake
Long Lake in Washington County, Minnesota has a water quality grade of D (Nutrient-rich). Water clarity: 2.8 ft visibility. Phosphorus: 47.5 µg/L. Chlorophyll-a (algae): 25.3 µg/L. Maximum depth: 60 ft. Surface area: 1799.22 acres.
- Clarity
- 2.8 ft
- Max depth
- 60 ft
- Area
- 1,799 acres
- Type
- Eutrophic
- Public access
- Yes
- Ice-out
- Apr 8
- Open water
- 241 days
Grade D measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Long Lake →
Next lake in Washington County
Long Lake is a 1,799-acre productive, nutrient-rich eutrophic lake in Washington County, Minnesota with a maximum depth of 60 feet. Water quality is graded D based on 2 sampling years through 2024. The lake supports 12 documented fish species including black bullhead, black crappie, and bluegill. Public access is available. Compared to the 74 other monitored lakes in Washington County, Long Lake ranks #47 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-14. 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.
Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum
Water Quality Grade: D (Nutrient-rich)
Very murky, less than 2.8 ft of visibility. Phosphorus level: 47.5 µg/L. Chlorophyll-a: 25.3 µg/L. Trophic State Index: 62.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.8 ft | Not graded |
| Phosphorus | 47.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 25.3 µg/L | Poor |
| Trophic State Index (TSI) | 62 | Eutrophic |
High nutrients, frequent algae, reduced clarity
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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Long Lake are listed below.
Top-rated places to stay near Long Lake
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Minnesota’s top lakes →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 60 ft |
| Surface Area | 1,799 acres |
| Shoreline Length | 16.8 mi |
| Littoral Zone | 64% |
| Public Access | Yes |
Fish Species
Click a species to see every graded lake where it is documented.
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.
Ice Season
Historical ice data from Minnesota DNR (8 observations).
Estimated open water season: 241 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2026-03-31 (2026) | 2014-04-25 (2014) |
| Ice-In | 2005-11-28 (2005) | 2004-12-14 (2004) |
Most recent ice-out: 2026-03-31
EPA Impairment Status
Long Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN82-0068-00 · Official waterbody report
County Ranking
Ranked #47 of 75 lakes in Washington County
Nearby Lakes With Higher Grades
Long Lake holds Grade D. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.
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 D (Nutrient-rich). Water clarity: 2.8 ft visibility. Phosphorus: 47.5 µg/L. Chlorophyll-a (algae): 25.3 µg/L. Maximum depth: 60 ft. Surface area: 1799.22 acres.
Is Long Lake safe to swim in?
- Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum. Long Lake has a water quality grade of D (Nutrient-rich). Algae concentration (chlorophyll-a) is 25.3 µg/L. Always check local health department advisories before swimming.
How deep is Long Lake?
- Long Lake has a maximum depth of 60 feet. The lake covers 1799.22 acres.
What fish are in Long Lake?
- Fish species found in Long Lake include black bullhead, black crappie, bluegill, brown bullhead, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, yellow bullhead, yellow perch. Long Lake is located in Washington County, Minnesota.
When does Long Lake thaw?
- Long Lake typically has ice-out around Apr 8. Ice typically forms around Dec 5. The open water season is approximately 241 days.
Explore Long Lake across LakeGrade
Fish species and top-graded lakes across Minnesota
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 grade
Lakes in the St. Croix Watershed, ranked by water quality
High nutrients, frequent algae, reduced clarity
Minnesota's cleanest and most-polluted lakes, ranked
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Where this data comes from
56 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
MNPCA56 samples · 2024
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- Analysis of Chlorophyll in Periphyton and Plankton
Monitoring station identifiers (2)
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