Green River Reservoir
Lamoille County, Vermont625 acresView mapDirections
Vermont DEC publishes the water-quality measurements for Green River Reservoir. Here is what has been measured.
- Oligotrophic
- Impaired · Hydrologic alteration
- 63 ft max depth
- Limited data
Green River Reservoir in Lamoille County, Vermont has water-quality measurements published by Vermont DEC, shown here as reported. Water clarity: 13.1 ft visibility. Phosphorus: 7.4 µg/L. Chlorophyll-a (algae): 1.4 µg/L. Surface area: 625 acres.
Green River Reservoir is a 625-acre cold, clear oligotrophic lake in Lamoille County, Vermont with an estimated average depth of about 63 feet. Overall water quality is declining over recent sampling years. Compared to the 5 other monitored lakes in Lamoille County, Green River Reservoir ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, VT DEC, last sampled 2025-08-18. Methodology: how these readings are compared.
Green River Reservoir covers about 630 acres in Lamoille County. Vrbo is where to look for cabins and lake homes around Green River Reservoir, and Booking.com and Expedia search hotels near the lake for your dates.
What Green River Reservoir is good for
From access and monitoring records, not editorial picks.
- Clear water13.1 ft of visibility
Swimming conditions
Readings onlyLimited data
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. Green River Reservoir is listed impaired under Clean Water Act §303(d) (IR 4C) for hydrologic alteration. Check local advisories before you swim.
Whether Green River Reservoir 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 Green River Reservoir
These are the measurements Vermont DEC publishes for Green River Reservoir, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 13.1 ft. Phosphorus 7.4 µg/L. Chlorophyll-a 1.4 µg/L. TSI 36.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 13.1ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 7.4µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 1.4µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 36 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Green River Reservoir
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~63 ft est.
Surface area
625 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 Green River Reservoir.
Lake Size & Watershed
Watershed (drainage) area
14 sq mi
HydroLAKES / HydroSHEDS
Shoreline
10.3 mi
HydroLAKES / HydroSHEDS
Elevation
1,207 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.
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Stays near Green River Reservoir
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Top-rated places to stay near Green River Reservoir
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Fishing Green River Reservoir
Water quality readings over time
3 seasons of samples on record (2021–2023). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening3 years
Reservoir Info (USACE NID)
Green River Reservoir is a man-made reservoir impounded by the Green River Dam (completed 1947), built primarily for hydroelectric on the Green River; arch-type dam, 105 ft tall and 360 ft long.
- Surface area
- 625 ac
- Normal storage
- 16,900 ac-ft
- Max storage
- 16,900 ac-ft
- Drainage area
- 14.6 sq mi
- Hazard class
- High
- Owner
- Village of Morrisville, VT
All listed purposes: Hydroelectric;Recreation.
Source: USACE National Inventory of Dams, NID ID VT00024 · Operator website
EPA Impairment Status
Green River Reservoir 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.
Source: EPA ATTAINS assessment unit VT07-18L03 · Official waterbody report
Nearby Lakes in Lamoille County
Frequently asked questions about Green River Reservoir
Where is Green River Reservoir?
- Green River Reservoir is a lake in Lamoille County, Vermont. Its water-quality measurements are published by Vermont DEC and shown on this page as reported.
What is the water quality of Green River Reservoir?
- Green River Reservoir in Lamoille County, Vermont has water-quality measurements published by Vermont DEC, shown here as reported. Water clarity: 13.1 ft visibility. Phosphorus: 7.4 µg/L. Chlorophyll-a (algae): 1.4 µg/L. Surface area: 625 acres.
Is Green River Reservoir safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Green River Reservoir is listed impaired under Clean Water Act §303(d) (IR 4C) for hydrologic alteration. Check local advisories before you swim.
How deep is Green River Reservoir?
- No published bathymetric survey covers Green River Reservoir, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 63 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 625 acres.
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Where this data comes from
48 measurements from 1 monitoring station, 2021–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Vermont Dept of Environmental Conservation
1VTDECWQ48 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 (1)
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)