Fern Lake
Addison County, VermontView mapDirections
Vermont DEC publishes the water-quality measurements for Fern Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Algal growth
- 42 ft max depth
Fern Lake in Addison County, Vermont has water-quality measurements published by Vermont DEC, shown here as reported. Water clarity: 20.7 ft visibility. Phosphorus: 19 µg/L. Chlorophyll-a (algae): 5.3 µg/L.
Fern Lake is a mesotrophic lake in Addison County, Vermont with an estimated average depth of about 42 feet. Overall water quality is improving over recent sampling years. Compared to the 4 other monitored lakes in Addison County, Fern Lake ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, VT DEC, last sampled 2025-08-23. Methodology: how these readings are compared.
What Fern Lake is good for
From access and monitoring records, not editorial picks.
- Clear water20.7 ft of visibility
Swimming conditions
Readings onlyRecreation use not supported
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. Fern Lake is listed impaired under Clean Water Act §303(d) (IR 4C) for algal growth, nuisance exotic species. Check local advisories before you swim.
Whether Fern Lake is safe to swim in today is a call for the Vermont Department of Environmental Conservation and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Fern Lake
These are the measurements Vermont DEC publishes for Fern Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Crystal clear, you can see 20.7 ft down. Phosphorus 19 µg/L. Chlorophyll-a 5.3 µg/L. TSI 42.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 20.7ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 19µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 5.3µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 42 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Fern Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~42 ft est.
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Vermont has not published bathymetry for Fern Lake.
Lake Size & Watershed
Watershed (drainage) area
1 sq mi
HydroLAKES / HydroSHEDS
Surface area
54 acres
HydroLAKES / HydroSHEDS
Shoreline
1.6 mi
HydroLAKES / HydroSHEDS
Elevation
591 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Stays via Stay22
Stays near Fern Lake
Compare lakeside cabins, hotels, and vacation rentals near Fern Lake in Addison County, Vermont — 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 Fern Lake
Prices for Oct 30–Nov 1, 4 adults. Change dates on the map below.
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 Vermont’s top lakes →
Follow Fern Lake’s readings
Email me when new measurements post for this lake. Updates stay free.
Or email
Fishing Fern Lake
Water Quality Trend: Improving
Based on 5 years of monitoring (2021–2025).
Water clarity
Improving4 years
Phosphorus
Worsening+6.06 µg/L/yr5 years
Chlorophyll-a
Improving-0.22 µg/L/yr5 years
EPA Impairment Status
Fern Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 4C).
Causes of impairment
Designated uses not supporting: Aquatic life, Recreation, Other.
Source: EPA ATTAINS assessment unit VT03-04L04_01 · Official waterbody report
Nearby Lakes in Addison County
Frequently asked questions about Fern Lake
Where is Fern Lake?
- Fern Lake is a lake in Addison County, Vermont. Its water-quality measurements are published by Vermont DEC and shown on this page as reported.
What is the water quality of Fern Lake?
- Fern Lake in Addison County, Vermont has water-quality measurements published by Vermont DEC, shown here as reported. Water clarity: 20.7 ft visibility. Phosphorus: 19 µg/L. Chlorophyll-a (algae): 5.3 µg/L.
Is Fern Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Fern Lake is listed impaired under Clean Water Act §303(d) (IR 4C) for algal growth, nuisance exotic species. Check local advisories before you swim.
How deep is Fern Lake?
- No published bathymetric survey covers Fern Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 42 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Explore Fern Lake across LakeQuality
More lakes in Vermont
Other Lakes in Vermont
Mesotrophic Lakes in Vermont
Where this data comes from
149 measurements from 2 monitoring stations, 2021–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Vermont Dept of Environmental Conservation
1VTDECWQ149 samples · 2021–2025
Analytical methods
- EPA approved Alternate Test Procedure for 4500 P H. Has a 28 day hold without acid preservation.
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- 2130 B ~ Nephelometric Method
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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)