Lake Mansfield
Lamoille County, Vermont38 acresView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
↑ up from B at the last regrade
- Mesotrophic
- #4 of 6 in the county
- 19 ft max depth
Lake Mansfield in Lamoille County, Vermont has a water quality grade of A (Excellent). Water clarity: 6.9 ft visibility. Phosphorus: 12.1 µg/L. Chlorophyll-a (algae): 3.1 µg/L. Surface area: 38 acres.
- Clarity
- 6.9 ft
- Max depth
- ~19 ft est.
- Area
- 38 acres
- Type
- Mesotrophic
- Phosphorus
- 12.1 µg/L
- Chlorophyll-a
- 3.1 µg/L
- Trend
- ↓ Declining
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Watch Lake Mansfield’s letter
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Lake Mansfield is a 38-acre mesotrophic lake in Lamoille County, Vermont with an estimated average depth of about 19 feet. Water quality is graded A based on 2 sampling years through 2024. Overall water quality is declining over recent sampling years. Compared to the 5 other monitored lakes in Lamoille County, Lake Mansfield ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, VT DEC, last sampled 2024-06-12. Grade methodology: LakeQuality methodology.
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. Check local advisories before you swim.
Water Quality Grade: A (Excellent)
Moderate clarity, visible to about 6.9 ft. Phosphorus 12.1 µg/L. Chlorophyll-a 3.1 µg/L. TSI 44. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 6.9 ft | Not graded |
| Phosphorus | 12.1 µg/L | Good |
| Chlorophyll-a (Algae) | 3.1 µg/L | Good |
| Trophic State Index (TSI) | 44 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~19 ft est. |
| Surface Area | 38 acres |
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 Mansfield.
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.
Fishing Lake Mansfield
Water Quality Trend: ↓ Declining
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Phosphorus | ↓ Declining | +4.9 µg/L/yr | 2 |
| Chlorophyll-a | ↓ Declining | +1.6 µg/L/yr | 2 |
Reservoir Info (USACE NID)
Lake Mansfield is a man-made reservoir impounded by the Lake Mansfield (completed 1900), built primarily for recreation on the Miller Brook; earth-type dam, 32 ft tall and 375 ft long.
- Surface area
- 38 ac
- Normal storage
- 0 ac-ft
- Max storage
- 515 ac-ft
- Drainage area
- 2.48 sq mi
- Hazard class
- High
- Owner
- LAKE MANSFIELD TROUT CLUB
Source: USACE National Inventory of Dams, NID ID VT00100 · Operator website
County Ranking
Ranked #4 of 6 lakes in Lamoille County
Nearby Lakes in Lamoille County
Frequently asked questions about Lake Mansfield
Where is Lake Mansfield?
- Lake Mansfield is a lake in Lamoille 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 Mansfield?
- Lake Mansfield in Lamoille County, Vermont has a water quality grade of A (Excellent). Water clarity: 6.9 ft visibility. Phosphorus: 12.1 µg/L. Chlorophyll-a (algae): 3.1 µg/L. Surface area: 38 acres.
Is Lake Mansfield safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
How deep is Lake Mansfield?
- No published bathymetric survey covers Lake Mansfield, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 19 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 38 acres.
Explore Lake Mansfield across LakeQuality
2 documented falls within 9.2 mi, nearest Bingham Falls
Species activity outlook by water temperature and season
Where to stay at Vermont's top lakes, each with its grade
Moderate nutrients, good water quality
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Where this data comes from
25 measurements from 1 monitoring station, 2021–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Vermont Dept of Environmental Conservation
1VTDECWQ25 samples · 2021–2024
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
- 2120 B ~ Color in Water by Visual Comparison
Monitoring station identifiers (1)
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
Lake size & watershed from HydroLAKES (HydroSHEDS)