Opechee Bay-Deep Spot Lake
Opechee Bay-Deep Spot Lake in Belknap County, New Hampshire has a water quality grade of B (Good). Phosphorus: 8.4 µg/L. Surface area: 46720 acres.
- Area
- 46,720 acres
- Type
- Oligotrophic
- Public access
- Yes
Opechee Bay-Deep Spot Lake is a 46,720-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 3 public boat landings. Compared to the 26 other monitored lakes in Belknap County, Opechee Bay-Deep Spot Lake ranks #18 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2025-08-10. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLow algae
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: 8.4 µg/L. Trophic State Index: 35.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 8.4 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 35 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Opechee Bay-Deep Spot Lake
Compare lakeside cabins, hotels, and vacation rentals near Opechee Bay-Deep Spot Lake 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.
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Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 46,720 acres |
| Public Access | Yes |
No bathymetric survey has been published for Opechee Bay-Deep Spot Lake, so its depth is not documented here.
Recreation & Access
- Messer StreetPublic
- Saltmarsh PondPublic
- Winnisquam LakePublic
Named access points from the USGS National Boat Ramps inventory, snapped within 5 km. More lakes with boat ramps
Fishing Opechee Bay-Deep Spot Lake
Reservoir Info (USACE NID)
Opechee Bay-Deep Spot Lake is a man-made reservoir impounded by the Lakeport (completed 1958), built primarily for hydroelectric on the Winnipesaukee River; concrete-type dam, 10 ft tall and 225 ft long.
- Surface area
- 46,720 ac
- Normal storage
- 165,800 ac-ft
- Max storage
- 165,800 ac-ft
- Drainage area
- 363 sq mi
- Hazard class
- Significant
All listed purposes: Hydroelectric;Recreation;Flood Risk Reduction.
Source: USACE National Inventory of Dams, NID ID NH00216 · Operator website · Matched by proximity (0.27 km)
EPA Impairment Status
Opechee Bay-Deep Spot Lake 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 NHLAK700020201-06-01 · Official waterbody report · Matched by proximity (0.56 km)
County Ranking
Ranked #18 of 27 lakes in Belknap County
Nearby Lakes in Belknap County
Frequently asked questions about Opechee Bay-Deep Spot Lake
Where is Opechee Bay-Deep Spot Lake?
- Opechee Bay-Deep Spot Lake 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 Opechee Bay-Deep Spot Lake?
- Opechee Bay-Deep Spot Lake in Belknap County, New Hampshire has a water quality grade of B (Good). Phosphorus: 8.4 µg/L. Surface area: 46720 acres.
Is Opechee Bay-Deep Spot Lake safe to swim in?
- Good for swimming, clear water with low algae levels. Opechee Bay-Deep Spot Lake has a water quality grade of B (Good). Always check local health department advisories before swimming.
Are there boat ramps on Opechee Bay-Deep Spot Lake?
- Opechee Bay-Deep Spot Lake has 3 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Messer Street, Saltmarsh Pond, Winnisquam Lake. Public access is listed as yes.
Explore Opechee Bay-Deep Spot Lake 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
32 measurements from 1 monitoring station, 2022–2025. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- New Hampshire Department Of Environmental Services (BEACH)
1111330032 samples · 2022–2025
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