Big Marine Lake
Washington County, MinnesotaView mapDirections
Minnesota PCA publishes the water-quality measurements for Big Marine Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Mercury
- 2 aquatic invasives
- Public access
Big Marine Lake in Washington County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 12 ft visibility. Phosphorus: 13 µg/L. Chlorophyll-a (algae): 4.6 µg/L.
Big Marine Lake is a mesotrophic lake in Washington County, Minnesota. Water clarity is improving over recent sampling years. Limited fish-species data available. Public access is available with 3 public boat landings. Compared to the 74 other monitored lakes in Washington County, Big Marine Lake ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-25. Methodology: how these readings are compared.
What Big Marine Lake is good for
From access and monitoring records, not editorial picks.
- Clear water12 ft of visibility
- Boat launch3 documented ramps
Swimming conditions
Readings onlyLow algae
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. Big Marine Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Big Marine 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 Big Marine Lake
These are the measurements Minnesota PCA publishes for Big Marine Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 12 ft. Phosphorus 13 µg/L. Chlorophyll-a 4.6 µg/L. TSI 43.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 12ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 13µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 4.6µg/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. | 43 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Big Marine Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Big Marine Lake typically sits around 54°F at the surface in October. Summer average is about 67°F. Usually warmest in Aug (about 70°F) and coldest in Apr (about 45°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (45°F) to its warmest (70°F).
Typical surface water temperature by month, from 313 field readings (2010–2024) via the EPA Water Quality Portal. See the full Big Marine Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Big Marine Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was moderate (26,546 cells/mL) on April 11, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Big Marine Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Public Water Access Sites — Big Marine (Main Lake)Public Water Access Sites · MN DNR LakeFinder
Recreation & Access
- Big Marine Lake (South)Public
- Big Marine Park ReservePublic
- Veterans CampgroundPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Big Marine Lake
Compare lakeside cabins, hotels, and vacation rentals near Big Marine 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 Big Marine 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 →
Follow Big Marine Lake’s readings
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Fishing Big Marine 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.
Water quality readings over time
3 seasons of samples on record (2020–2024). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Improving3 years
Phosphorus
Stable-0.37 µg/L/yr3 years
Chlorophyll-a
Worsening+0.15 µg/L/yr3 years
EPA Impairment Status
Big Marine Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN82-0052-04 · Official waterbody report
Nearby Lakes in Washington County
Frequently asked questions about Big Marine Lake
Where is Big Marine Lake?
- Big Marine 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 Big Marine Lake?
- Big Marine Lake in Washington County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 12 ft visibility. Phosphorus: 13 µg/L. Chlorophyll-a (algae): 4.6 µg/L.
Is Big Marine Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Big Marine Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
What is the water temperature of Big Marine Lake?
- Big Marine Lake typically sits around 54°F at the surface in October, from 313 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
Does Big Marine Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Big Marine Lake (clouds, ice, or an off-season gap). The most recent reading was moderate (26,546 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Big Marine Lake?
- Big Marine Lake has 3 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Big Marine Lake (South), Big Marine Park Reserve, Veterans Campground. Public access is listed as yes.
Can I fish at Big Marine Lake?
- Big Marine Lake has 3 documented boat landings in the USGS National Boat Ramps inventory. 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 Big Marine Lake across LakeQuality
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Where this data comes from
102 measurements from 1 monitoring station, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA102 samples · 2020–2024
Analytical methods
- Field measurement/observation, generic method
- Total Phosphorus After Block Digestion
- Phosphorus by Colorimetry
- Analysis of Chlorophyll in Periphyton and Plankton
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
Named boat-access points from the USGS National Boat Ramps inventory