Knapp Brook Lake
Windsor County, Vermont35 acresView mapDirections
Not Rated: two monitoring stations are on record, but they measured water clarity only. LakeQuality’s A–F method grades total phosphorus, total nitrogen, chlorophyll-a, and turbidity; clarity is shown, not scored.
- 48 ft max depth
- Public access
- Limited data
Knapp Brook Lake in Windsor County, Vermont is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 3.6 ft visibility. Surface area: 35 acres.
- Clarity
- 3.6 ft
- Max depth
- ~48 ft est.
- Area
- 35 acres
- Trend
- ↑ Improving
- Public access
- Yes
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Watch Knapp Brook Lake’s letter
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Why Knapp Brook Lake has no grade
Knapp Brook Lake has monitoring on record from two stations, but only water clarity was measured. LakeQuality’s A–F letter uses total phosphorus, total nitrogen, chlorophyll-a, and turbidity against EPA National Lakes Assessment condition classes. With none of those grading measurements on record, Knapp Brook Lake is Not Rated — not an F. Its 3.6-foot median from 40 readings collected 2020–2024 is still shown as clarity, but clarity alone cannot earn a letter.
Not Rated is EPA Integrated Reporting Category 3 — insufficient information. Everything below that has been measured is still reported on this page.
Sampling is run by VT DEC and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Knapp Brook Lake is a 35-acre lake in Windsor County, Vermont with an estimated average depth of about 48 feet. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available.
Source: EPA Water Quality Portal sampling records, VT DEC, last sampled 2024-05-02. Grade methodology: LakeQuality methodology.
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Check local advisories before you swim.
Water quality measurements for Knapp Brook Lake
These readings exist but are not enough for an A–F grade — see why.
Murky, only visible to about 3.6 ft. TSI 59.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.6 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 59 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~48 ft est. |
| Average Depth | ~17 ft est. |
| Surface Area | 35 acres |
| 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 Knapp Brook Lake.
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 Knapp Brook Lake
Water Quality Trend: ↑ Improving
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.25 m/yr | 3 |
Reservoir Info (USACE NID)
Knapp Brook Lake is a man-made reservoir impounded by the Knapp Brook Site No. 2 (completed 1961), built primarily for recreation on the Knapp Brook; earth-type dam, 27 ft tall and 540 ft long.
- Surface area
- 35 ac
- Normal storage
- 0 ac-ft
- Max storage
- 623 ac-ft
- Drainage area
- 2.92 sq mi
- Hazard class
- Significant
- Owner
- STATE OF VERMONT - DFW
Source: USACE National Inventory of Dams, NID ID VT00077 · Operator website · Matched by proximity (0.13 km)
Graded lakes near Knapp Brook Lake
Knapp Brook Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Windsor County
Frequently asked questions about Knapp Brook Lake
Where is Knapp Brook Lake?
- Knapp Brook Lake is a lake in Windsor County, Vermont. LakeQuality has not rated this lake (UNRATED) — the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity.
What is the water quality grade for Knapp Brook Lake?
- Knapp Brook Lake in Windsor County, Vermont is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 3.6 ft visibility. Surface area: 35 acres.
Is Knapp Brook Lake safe to swim in?
- The letter is not a swimming clearance. Check local advisories before you swim.
How deep is Knapp Brook Lake?
- No published bathymetric survey covers Knapp Brook Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 48 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 35 acres.
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Where this data comes from
40 measurements from 2 monitoring stations, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Vermont Dept of Environmental Conservation
1VTDECWQ40 samples · 2020–2024
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
Monitoring station identifiers (2)
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)