Lake Willoughby
Orleans County, VermontView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
- Oligotrophic
- Impaired · Nuisance exotic species
- #4 of 17 in the county
- 75 ft max depth
- Public access
Lake Willoughby in Orleans County, Vermont has a water quality grade of A (Excellent). Water clarity: 28.2 ft visibility. Phosphorus: 7.8 µg/L. Chlorophyll-a (algae): 1.6 µg/L.
- Clarity
- 28.2 ft
- Max depth
- ~75 ft est.
- Type
- Oligotrophic
- Phosphorus
- 7.8 µg/L
- Chlorophyll-a
- 1.6 µg/L
- Trend
- ↑ Improving
- Public access
- Yes
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Watch Lake Willoughby’s letter
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Lake Willoughby is a cold, clear oligotrophic lake in Orleans County, Vermont with an estimated average depth of about 75 feet. Water quality is graded A based on 2 sampling years through 2025. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 16 other monitored lakes in Orleans County, Lake Willoughby ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, VT DEC, last sampled 2025-08-13. Grade methodology: LakeQuality methodology.
What Lake Willoughby is good for
From access and monitoring records, not editorial picks.
- Clear water28.2 ft of visibility
- Boat launch1 documented ramp
Swimming Safety
Grade onlyLow algae
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.
The A is nutrients and algae, not a swimming clearance. Lake Willoughby is listed impaired under Clean Water Act §303(d) (IR 4C) for nuisance exotic species. Check local advisories before you swim.
Water Quality Grade: A (Excellent)
Crystal clear, you can see 28.2 ft down. Phosphorus 7.8 µg/L. Chlorophyll-a 1.6 µg/L. TSI 33. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 28.2 ft | Not graded |
| Phosphorus | 7.8 µg/L | Good |
| Chlorophyll-a (Algae) | 1.6 µg/L | Good |
| Trophic State Index (TSI) | 33 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~75 ft est. |
| Public Access | Yes |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Vermont has not published bathymetry for Lake Willoughby.
Lake Size & Watershed
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.
Recreation & Access
- Lake WilloughbyPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Lake Willoughby
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.533 m/yr | 5 |
| Phosphorus | ↑ Improving | -0.35 µg/L/yr | 6 |
| Chlorophyll-a | ↑ Improving | -0.31 µg/L/yr | 6 |
EPA Impairment Status
Lake Willoughby is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 4C).
Causes of impairment
Source: EPA ATTAINS assessment unit VT17-06L02_02 · Official waterbody report
County Ranking
Ranked #4 of 17 lakes in Orleans County
Nearby Lakes in Orleans County
Frequently asked questions about Lake Willoughby
Where is Lake Willoughby?
- Lake Willoughby is a lake in Orleans County, Vermont. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Lake Willoughby?
- Lake Willoughby in Orleans County, Vermont has a water quality grade of A (Excellent). Water clarity: 28.2 ft visibility. Phosphorus: 7.8 µg/L. Chlorophyll-a (algae): 1.6 µg/L.
Is Lake Willoughby safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Lake Willoughby is listed impaired under Clean Water Act §303(d) (IR 4C) for nuisance exotic species. Check local advisories before you swim.
How deep is Lake Willoughby?
- No published bathymetric survey covers Lake Willoughby, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 75 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Are there boat ramps on Lake Willoughby?
- Lake Willoughby has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Lake Willoughby. Public access is listed as yes.
Explore Lake Willoughby across LakeQuality
Species activity outlook by water temperature and season
Where to stay at Vermont's top lakes, each with its grade
Low nutrients, clear water. The letter is not a swimming clearance.
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Where this data comes from
299 measurements from 3 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Vermont Dept of Environmental Conservation
1VTDECWQ299 samples · 2020–2025
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 (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 size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory