Long Lake
Washington County, Minnesota1,799 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Long Lake. Here is what has been measured.
- Eutrophic
- 2 aquatic invasives
- 60 ft max depth
- Public access
- Limited data
Long Lake in Washington County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. 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.
Minnesota DNR's Targeted Survey on July 29, 2024 caught 0.25 walleye per gill net at Long Lake. DNR survey details →
Long Lake is a 1,799-acre productive, nutrient-rich eutrophic lake in Washington County, Minnesota with a maximum depth of 60 feet. 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. Methodology: how these readings are compared.
What Long Lake is good for
From access and monitoring records, not editorial picks.
- Fishing12 species recorded
- Ice seasonIce-out around Apr 8
- Deep water60 ft surveyed max depth
- Big water1,799 acres
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 Long 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 Long Lake
These are the measurements Minnesota PCA publishes for Long 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 2.8 ft of visibility. Phosphorus 47.5 µg/L. Chlorophyll-a 25.3 µg/L. TSI 62.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.8ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 47.5µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 25.3µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 62 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Long Lake
Answers come straight from the public measurements and survey records on this page.
Minnesota DNR's Targeted Survey on July 29, 2024 caught 0.25 walleye per gill net at Long Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Long Lake’s water-quality measurements separately. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
23 surveys on file from MN DNR Fisheries. Most recent: 2024-07-29 (Targeted Survey).
23 surveys on file · most recent 2024-07-29 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluntnose Minnow | 37.28 | ||
| Bluegill | 35.71 | 4–8 in 2024-07-29 | 0.15 lb |
| Golden Shiner | 12.06 | 5 in 2024-07-29 | 0.07 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.
Length Distributions
Number of fish caught at each inch class in the most recent survey that recorded lengths. Red dashed line marks an approximate trophy threshold for that species.
Bluegill
Golden Shiner
From the 2024-07-29 survey
Big Marine Lake is a 1,799 acre, class 24 lake located in northern Washington County. Big Marine Lake is mesotrophic, moderately fertile, and is primarily managed for Walleye and Largemouth Bass. Bluegill and Black Crappie are secondary management species. From 1995 to 2017, Big Marine Lake was stocked with Walleye…
Lake Details
Max depth
60 ft
Surface area
1,799 acres
Shoreline
16.8 mi
Littoral zone
64%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Stays via Stay22
Stays 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 readings cover nutrients and algae, not lodging. Cabins and rentals around Long Lake are listed below.
Top-rated places to stay near Long Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
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Fish Species
Click a species to see every 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
Typical ice-out
Apr 8
Earliest Mar 31, 2026 · Latest Apr 25, 2014
Typical ice-in
Dec 5
Earliest Nov 28, 2005 · Latest Dec 14, 2004
Most recent ice-out
Mar 31
2026
8 observations · Minnesota PCA ice records
Nearby Lakes in Washington County
Frequently asked questions about Long Lake
Where is Long Lake?
- Long 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 Long Lake?
- Long Lake in Washington County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. 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?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
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.
What did the DNR fisheries survey find at Long Lake?
- Minnesota DNR's Targeted Survey on July 29, 2024 caught 0.25 walleye per gill net at Long Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Long Lake’s water-quality measurements separately. Catch rate is not a swim clearance and is not a weekly bite report.
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.
Can I fish at Long Lake?
- Public access to Long 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 Long Lake across LakeQuality
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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)
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
Ice data from Minnesota DNR Climate