Lake Sunapee
Lake Sunapee in Sullivan County, New Hampshire is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 26.7 ft visibility. Surface area: 4090 acres.
- Clarity
- 26.7 ft
- Area
- 4,090 acres
Why Lake Sunapee has no grade
We grade a lake only when its monitoring record clears the evidence bar: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Lake Sunapee, 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. Sampling here has recorded water clarity, but not phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by your state environmental agency and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Lake Sunapee is a 4,090-acre lake in Sullivan County, New Hampshire.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2024-07-18. Grade methodology: LakeGrade methodology.
Watch Lake Sunapee water quality
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Lake Sunapee
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Crystal clear, you can see 26.7 ft down. Trophic State Index: 30.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 26.7 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 30 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Lake Sunapee
Compare lakeside cabins, hotels, and vacation rentals near Lake Sunapee in Sullivan County, New Hampshire — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Lake Sunapee
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 4,090 acres |
No bathymetric survey has been published for Lake Sunapee, so its depth is not documented here.
Fishing Lake Sunapee
Reservoir Info (USACE NID)
Lake Sunapee 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
EPA Impairment Status
Lake Sunapee is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NHLAK801060402-05-01 · Official waterbody report
Graded lakes near Lake Sunapee
Lake Sunapee has no grade, but these lakes within a short drive do.
Nearby Lakes in Sullivan County
Frequently asked questions about Lake Sunapee
Where is Lake Sunapee?
- Lake Sunapee is a lake in Sullivan County, New Hampshire. LakeQuality has not rated this lake (UNRATED) — there is not enough recent sampling to assign a letter.
What is the water quality grade for Lake Sunapee?
- Lake Sunapee in Sullivan County, New Hampshire is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 26.7 ft visibility. Surface area: 4090 acres.
Is Lake Sunapee safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Lake Sunapee is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
Explore Lake Sunapee across LakeGrade
More New Hampshire Lake Rankings
Top 25 by overall water quality score
Top 25 by Secchi water clarity
Grade A/B + low algae filter
Panfish-rich, public access
Full state directory
Other Lakes in New Hampshire
Oligotrophic Lakes in New Hampshire
Where this data comes from
6 measurements from 1 monitoring station, 2024. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- North American Lake Management Society
NALMS6 samples · 2024
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
Impairment status from EPA ATTAINS 303(d) database