Lake Groton
Caledonia County, Vermont414 acresView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
- Mesotrophic
- #3 of 9 in the county
- 43 ft max depth
Lake Groton in Caledonia County, Vermont has a water quality grade of A (Excellent). Water clarity: 13.1 ft visibility. Phosphorus: 11.3 µg/L. Chlorophyll-a (algae): 3.3 µg/L. Surface area: 414 acres.
- Clarity
- 13.1 ft
- Max depth
- ~43 ft est.
- Area
- 414 acres
- Type
- Mesotrophic
- Phosphorus
- 11.3 µg/L
- Chlorophyll-a
- 3.3 µg/L
- Trend
- ↑ Improving
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Watch Lake Groton’s letter
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Lake Groton is a 414-acre mesotrophic lake in Caledonia County, Vermont with an estimated average depth of about 43 feet. Water quality is graded A based on 2 sampling years through 2025. Overall water quality is improving over recent sampling years. Compared to the 8 other monitored lakes in Caledonia County, Lake Groton ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, VT DEC, last sampled 2025-08-21. Grade methodology: LakeQuality methodology.
What Lake Groton is good for
From access and monitoring records, not editorial picks.
- Clear water13.1 ft of visibility
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)
Good clarity, visible to about 13.1 ft. Phosphorus 11.3 µg/L. Chlorophyll-a 3.3 µg/L. TSI 40. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 13.1 ft | Not graded |
| Phosphorus | 11.3 µg/L | Good |
| Chlorophyll-a (Algae) | 3.3 µg/L | Good |
| Trophic State Index (TSI) | 40 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~43 ft est. |
| Average Depth | ~29 ft est. |
| Surface Area | 414 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 Groton.
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 Groton
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.286 m/yr | 6 |
| Phosphorus | ↑ Improving | -0.73 µg/L/yr | 6 |
| Chlorophyll-a | ↑ Improving | -0.31 µg/L/yr | 6 |
Reservoir Info (USACE NID)
Lake Groton is a man-made reservoir impounded by the Lake Groton (completed 1968), built primarily for recreation on the Ricker Pond-Tr; concrete-type dam, 13 ft tall and 598 ft long.
- Surface area
- 414 ac
- Normal storage
- 0 ac-ft
- Max storage
- 5,148 ac-ft
- Drainage area
- 18.75 sq mi
- Hazard class
- Low
- Owner
- STATE OF VERMONT - DEC
Source: USACE National Inventory of Dams, NID ID VT00088 · Operator website
County Ranking
Ranked #3 of 9 lakes in Caledonia County
Nearby Lakes in Caledonia County
Frequently asked questions about Lake Groton
Where is Lake Groton?
- Lake Groton is a lake in Caledonia 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 Groton?
- Lake Groton in Caledonia County, Vermont has a water quality grade of A (Excellent). Water clarity: 13.1 ft visibility. Phosphorus: 11.3 µg/L. Chlorophyll-a (algae): 3.3 µg/L. Surface area: 414 acres.
Is Lake Groton safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
How deep is Lake Groton?
- No published bathymetric survey covers Lake Groton, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 43 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 414 acres.
Explore Lake Groton across LakeQuality
More Vermont Lake Rankings
Other Grade A Lakes in Vermont
Mesotrophic Lakes in Vermont
Where this data comes from
151 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Vermont Dept of Environmental Conservation
1VTDECWQ151 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
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)