Opechee Bay-Deep Spot Lake
Belknap County, New Hampshire46,720 acresView mapDirections
NHDES publishes the water-quality measurements for Opechee Bay-Deep Spot Lake. Here is what has been measured.
- Oligotrophic
- Impaired · Mercury
- Public access
Opechee Bay-Deep Spot Lake in Belknap County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 8.4 µg/L. Surface area: 46720 acres.
Opechee Bay-Deep Spot Lake is a 46,720-acre cold, clear oligotrophic lake in Belknap County, New Hampshire. Limited fish-species data available. Public access is available with 2 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. Methodology: how these readings are compared.
What Opechee Bay-Deep Spot Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch2 documented ramps
- Big water46,720 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. Opechee Bay-Deep Spot Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury, nuisance exotic species. Check local advisories before you swim.
Whether Opechee Bay-Deep Spot 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 Opechee Bay-Deep Spot Lake
These are the measurements NHDES publishes for Opechee Bay-Deep Spot 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 8.4 µg/L. TSI 35.
| 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 | 8.4µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 35 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Opechee Bay-Deep Spot Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
46,720 acres
Public access
Yes
Listed by NHDES
No bathymetric survey has been published for Opechee Bay-Deep Spot Lake, so its depth is not documented here.
Recreation & Access
- Messer StreetPublic
- Glendale DocksPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
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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
Designated uses not supporting: Aquatic life, Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NHLAK700020201-06-01 · Official waterbody report
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. Its water-quality measurements are published by NHDES and shown on this page as reported.
What is the water quality of Opechee Bay-Deep Spot Lake?
- Opechee Bay-Deep Spot Lake in Belknap County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 8.4 µg/L. Surface area: 46720 acres.
Is Opechee Bay-Deep Spot Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Opechee Bay-Deep Spot Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury, nuisance exotic species. Check local advisories before you swim.
Are there boat ramps on Opechee Bay-Deep Spot Lake?
- Opechee Bay-Deep Spot Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Messer Street, Glendale Docks. Public access is listed as yes.
Can I fish at Opechee Bay-Deep Spot Lake?
- Opechee Bay-Deep Spot Lake has 2 documented boat landings 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.
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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)
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
Named boat-access points from the USGS National Boat Ramps inventory