Forest Lake-Deep Spot
Cheshire County, New Hampshire93 acresView mapDirections
NHDES publishes the water-quality measurements for Forest Lake-Deep Spot. Here is what has been measured.
- Mesotrophic
- Impaired · Algal growth
Forest Lake-Deep Spot in Cheshire County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 14.5 µg/L. Chlorophyll-a (algae): 5 µg/L. Surface area: 93 acres.
Forest Lake-Deep Spot is a 93-acre mesotrophic lake in Cheshire County, New Hampshire. Compared to the 37 other monitored lakes in Cheshire County, Forest Lake-Deep Spot ranks #28 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2025-06-02. Methodology: how these readings are compared.
Swimming conditions
Readings onlyBacteria advisory
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. Forest Lake-Deep Spot is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, biotoxins, mercury, nuisance exotic species, nutrients (phosphorus, nitrogen), pH / acidity. Check local advisories before you swim.
Whether Forest Lake-Deep Spot 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 Forest Lake-Deep Spot
These are the measurements NHDES publishes for Forest Lake-Deep Spot, 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 14.5 µg/L. Chlorophyll-a 5 µg/L. TSI 45.
| 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 | 14.5µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 5µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 45 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Forest Lake-Deep Spot
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
93 acres
No bathymetric survey has been published for Forest Lake-Deep Spot, so its depth is not documented here.
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Stays near Forest Lake-Deep Spot
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Fishing Forest Lake-Deep Spot
Reservoir Info (USACE NID)
Forest Lake-Deep Spot is a man-made reservoir impounded by the Forest Lake Dam (completed 1915), built primarily for recreation on the Tr Ashuelot River; earth-type dam, 8 ft tall and 75 ft long.
- Surface area
- 93 ac
- Normal storage
- 164 ac-ft
- Max storage
- 378 ac-ft
- Drainage area
- 6.82 sq mi
- Hazard class
- Low
- Owner
- FOREST LAKE IMPROVEMENT ASSOC
Source: USACE National Inventory of Dams, NID ID NH00297 · Operator website · Matched by proximity (0.46 km)
EPA Impairment Status
Forest Lake-Deep Spot is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life, Fish consumption, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NHLAK802010401-01-01 · Official waterbody report
Nearby Lakes in Cheshire County
Frequently asked questions about Forest Lake-Deep Spot
Where is Forest Lake-Deep Spot?
- Forest Lake-Deep Spot is a lake in Cheshire County, New Hampshire. Its water-quality measurements are published by NHDES and shown on this page as reported.
What is the water quality of Forest Lake-Deep Spot?
- Forest Lake-Deep Spot in Cheshire County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 14.5 µg/L. Chlorophyll-a (algae): 5 µg/L. Surface area: 93 acres.
Is Forest Lake-Deep Spot safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Forest Lake-Deep Spot is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, biotoxins, mercury, nuisance exotic species, nutrients (phosphorus, nitrogen), pH / acidity. Check local advisories before you swim.
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Where this data comes from
27 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- New Hampshire Department Of Environmental Services (BEACH)
1111330027 samples · 2020–2025
Analytical methods
- 10-115-01-1 F ~ LACHAT; Total Phosphorus- Manual persulfate digest
- CHLOROPHYLL A-B-C DETERMINATION (MODIFIED)
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