Deering Reservoir-Deep Spot
Hillsborough County, New Hampshire323 acresView mapDirections
NHDES publishes the water-quality measurements for Deering Reservoir-Deep Spot. Here is what has been measured.
- Mesotrophic
- Impaired · Mercury
- Public access
Deering Reservoir-Deep Spot in Hillsborough County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 9.6 µg/L. Chlorophyll-a (algae): 3 µg/L. Surface area: 323 acres.
Deering Reservoir-Deep Spot is a 323-acre mesotrophic lake in Hillsborough County, New Hampshire. Limited fish-species data available. Public access is available. Compared to the 35 other monitored lakes in Hillsborough County, Deering Reservoir-Deep Spot ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2025-08-05. Methodology: how these readings are compared.
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. Deering Reservoir-Deep Spot is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, oxygen depletion (low DO), pH / acidity. Check local advisories before you swim.
Whether Deering Reservoir-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 Deering Reservoir-Deep Spot
These are the measurements NHDES publishes for Deering Reservoir-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 9.6 µg/L. Chlorophyll-a 3 µg/L. TSI 39.
| 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 | 9.6µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 3µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 39 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Deering Reservoir-Deep Spot
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
323 acres
Public access
Yes
Listed by NHDES
No bathymetric survey has been published for Deering Reservoir-Deep Spot, so its depth is not documented here.
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Fishing Deering Reservoir-Deep Spot
Reservoir Info (USACE NID)
Deering Reservoir-Deep Spot is a man-made reservoir impounded by the Deering Reservoir Dam (completed 1940), built primarily for recreation on the Piscataquog River; earth-type dam, 25 ft tall and 873 ft long.
- Surface area
- 323 ac
- Normal storage
- 2,730 ac-ft
- Max storage
- 3,143 ac-ft
- Drainage area
- 4.3 sq mi
- Hazard class
- High
- Owner
- NH DES WATER DIVISION
Source: USACE National Inventory of Dams, NID ID NH00282 · Operator website · Matched by proximity (0.6 km)
EPA Impairment Status
Deering Reservoir-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.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NHLAK700060601-01 · Official waterbody report
Nearby Lakes in Hillsborough County
Frequently asked questions about Deering Reservoir-Deep Spot
Where is Deering Reservoir-Deep Spot?
- Deering Reservoir-Deep Spot is a lake in Hillsborough County, New Hampshire. Its water-quality measurements are published by NHDES and shown on this page as reported.
What is the water quality of Deering Reservoir-Deep Spot?
- Deering Reservoir-Deep Spot in Hillsborough County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 9.6 µg/L. Chlorophyll-a (algae): 3 µg/L. Surface area: 323 acres.
Is Deering Reservoir-Deep Spot safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Deering Reservoir-Deep Spot is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, oxygen depletion (low DO), pH / acidity. Check local advisories before you swim.
Can I fish at Deering Reservoir-Deep Spot?
- Public access to Deering Reservoir-Deep Spot is listed as yes on the lake record. 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
65 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)
1111330065 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