Sunapee Lake
Sullivan County, New Hampshire4,090 acresView mapDirections
NHDES publishes the water-quality measurements for Sunapee Lake. Here is what has been measured.
- Oligotrophic
- Public access
Sunapee Lake in Sullivan County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 5 µg/L. Chlorophyll-a (algae): 1.1 µg/L. Surface area: 4090 acres.
Sunapee Lake is a 4,090-acre cold, clear oligotrophic lake in Sullivan County, New Hampshire. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 23 other monitored lakes in Sullivan County, Sunapee Lake ranks #12 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2024-09-16. Methodology: how these readings are compared.
What Sunapee Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Big water4,090 acres
Swimming conditions
Readings onlyLow algae
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. Check local advisories before you swim.
Whether Sunapee Lake is safe to swim in today is a call for the New Hampshire Department of Environmental Services and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Sunapee Lake
These are the measurements NHDES publishes for Sunapee Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Phosphorus 5 µg/L. Chlorophyll-a 1.1 µg/L. TSI 29.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer. | |
| Total phosphorus | 5µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 1.1µg/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. | 29 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Sunapee Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
4,090 acres
Public access
Yes
Listed by NHDES
No bathymetric survey has been published for Sunapee Lake, so its depth is not documented here.
Recreation & Access
- Sunapee HarborPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Sunapee Lake
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Top-rated places to stay near Sunapee Lake
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Fishing Sunapee Lake
Reservoir Info (USACE NID)
Sunapee Lake is a man-made reservoir impounded by the Sunapee Lake Dam (completed 1872), built primarily for recreation on the Sugar River; concrete-type dam, 14 ft tall and 80 ft long.
- Surface area
- 4,090 ac
- Normal storage
- 19,800 ac-ft
- Max storage
- 40,900 ac-ft
- Drainage area
- 44.8 sq mi
- Hazard class
- Significant
- Owner
- NH DES WATER DIVISION
Source: USACE National Inventory of Dams, NID ID NH00108 · Operator website
Nearby Lakes in Sullivan County
Frequently asked questions about Sunapee Lake
Where is Sunapee Lake?
- Sunapee Lake is a lake in Sullivan County, New Hampshire. Its water-quality measurements are published by NHDES and shown on this page as reported.
What is the water quality of Sunapee Lake?
- Sunapee Lake in Sullivan County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 5 µg/L. Chlorophyll-a (algae): 1.1 µg/L. Surface area: 4090 acres.
Is Sunapee Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Are there boat ramps on Sunapee Lake?
- Sunapee Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Sunapee Harbor. Public access is listed as yes.
Can I fish at Sunapee Lake?
- Sunapee Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by New Hampshire's fish and wildlife agency, so check its current regulations before you go.
Explore Sunapee Lake across LakeQuality
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Where this data comes from
76 measurements from 6 monitoring stations, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- New Hampshire Department Of Environmental Services (BEACH)
1111330076 samples · 2020–2024
Analytical methods
- Phosphorus by Two Reagent Colorimetry
- CHLOROPHYLL A-B-C DETERMINATION (MODIFIED)
Monitoring station identifiers (6)
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
Named boat-access points from the USGS National Boat Ramps inventory