Crystal Lake-Outlet
Crystal Lake-Outlet in Belknap County, New Hampshire has a water quality grade of B (Good). Phosphorus: 11.6 µg/L. Surface area: 1155 acres.
- Area
- 1,155 acres
- Type
- Oligotrophic
- Public access
- Yes
Crystal Lake-Outlet is a 1,155-acre cold, clear oligotrophic lake in Belknap County, New Hampshire. Water quality is graded B based on 1 sampling years through 2025. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 26 other monitored lakes in Belknap County, Crystal Lake-Outlet ranks #12 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2025-08-25. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyBacteria advisory
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.
Good for swimming, clear water with low algae levels
Water Quality Grade: B (Good)
No clarity data. Phosphorus level: 11.6 µg/L. Trophic State Index: 39.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 11.6 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 39 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Crystal Lake-Outlet
Compare lakeside cabins, hotels, and vacation rentals near Crystal Lake-Outlet in Belknap 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 Crystal Lake-Outlet
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Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 1,155 acres |
| Public Access | Yes |
No bathymetric survey has been published for Crystal Lake-Outlet, so its depth is not documented here.
Recreation & Access
- Crystal LakePublic
Named access points from the USGS National Boat Ramps inventory, snapped within 5 km. More lakes with boat ramps
Fishing Crystal Lake-Outlet
Reservoir Info (USACE NID)
Crystal Lake-Outlet is a man-made reservoir impounded by the Crystal Lake Dam (completed 1881), built primarily for recreation on the Mascoma River; concrete-type dam, 18 ft tall and 575 ft long.
- Surface area
- 1,155 ac
- Normal storage
- 8,332 ac-ft
- Max storage
- 18,300 ac-ft
- Drainage area
- 153 sq mi
- Hazard class
- High
- Owner
- NH DES WATER DIVISION
Source: USACE National Inventory of Dams, NID ID NH00018 · Operator website · Matched by proximity (0.03 km)
EPA Impairment Status
Crystal Lake-Outlet is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NHLAK700060401-02-02 · Official waterbody report · Matched by proximity (0.97 km)
County Ranking
Ranked #12 of 27 lakes in Belknap County
Nearby Lakes in Belknap County
Frequently asked questions about Crystal Lake-Outlet
Where is Crystal Lake-Outlet?
- Crystal Lake-Outlet is a lake in Belknap County, New Hampshire. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Crystal Lake-Outlet?
- Crystal Lake-Outlet in Belknap County, New Hampshire has a water quality grade of B (Good). Phosphorus: 11.6 µg/L. Surface area: 1155 acres.
Is Crystal Lake-Outlet safe to swim in?
- Good for swimming, clear water with low algae levels. Crystal Lake-Outlet has a water quality grade of B (Good). Always check local health department advisories before swimming.
Are there boat ramps on Crystal Lake-Outlet?
- Crystal Lake-Outlet has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Crystal Lake. Public access is listed as yes.
Explore Crystal Lake-Outlet 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 Grade B Lakes in New Hampshire
Oligotrophic Lakes in New Hampshire
Where this data comes from
17 measurements from 1 monitoring station, 2021–2025. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- New Hampshire Department Of Environmental Services (BEACH)
1111330017 samples · 2021–2025
Analytical methods
- 10-115-01-1 F ~ LACHAT; Total Phosphorus- Manual persulfate digest
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
Named boat-access points from the USGS National Boat Ramps inventory