Giles Pond-Deep Spot
Merrimack County, New Hampshire43 acresView mapDirections
NHDES publishes the water-quality measurements for Giles Pond-Deep Spot. Here is what has been measured.
- Impaired · Mercury
- Public access
- Limited data
Giles Pond-Deep Spot in Merrimack County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 13.4 µg/L. Chlorophyll-a (algae): 5.2 µg/L. Surface area: 43 acres.
Giles Pond-Deep Spot is a 43-acre lake in Merrimack County, New Hampshire. Limited fish-species data available. Public access is available.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2020-06-11. Methodology: how these readings are compared.
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Giles Pond-Deep Spot is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, pH / acidity. Check local advisories before you swim.
Whether Giles Pond-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 Giles Pond-Deep Spot
These are the measurements NHDES publishes for Giles Pond-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 13.4 µg/L. Chlorophyll-a 5.2 µg/L. TSI 44.
| 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 | 13.4µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 5.2µg/L | Measured, not scored 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. | 44 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Giles Pond-Deep Spot
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
43 acres
Public access
Yes
Listed by NHDES
No bathymetric survey has been published for Giles Pond-Deep Spot, so its depth is not documented here.
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Fishing Giles Pond-Deep Spot
Reservoir Info (USACE NID)
Giles Pond-Deep Spot is a man-made reservoir impounded by the Giles Pond (completed 1904), built primarily for hydroelectric on the Salmon Brook; masonry-type dam, 18 ft tall and 245 ft long.
- Surface area
- 43 ac
- Normal storage
- 860 ac-ft
- Max storage
- 860 ac-ft
- Drainage area
- 25 sq mi
- Hazard class
- Low
- Owner
- Franklin Falls Hydro Electric Corporation
Source: USACE National Inventory of Dams, NID ID NH00177 · Operator website · Matched by proximity (0.21 km)
EPA Impairment Status
Giles Pond-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 NHLAK700010802-02 · Official waterbody report
Nearby Lakes in Merrimack County
Frequently asked questions about Giles Pond-Deep Spot
Where is Giles Pond-Deep Spot?
- Giles Pond-Deep Spot is a lake in Merrimack County, New Hampshire. Its water-quality measurements are published by NHDES and shown on this page as reported.
What is the water quality of Giles Pond-Deep Spot?
- Giles Pond-Deep Spot in Merrimack County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 13.4 µg/L. Chlorophyll-a (algae): 5.2 µg/L. Surface area: 43 acres.
Is Giles Pond-Deep Spot safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Giles Pond-Deep Spot is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, pH / acidity. Check local advisories before you swim.
Can I fish at Giles Pond-Deep Spot?
- Public access to Giles Pond-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
2 measurements from 1 monitoring station, 2020. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- New Hampshire Department Of Environmental Services (BEACH)
111133002 samples · 2020
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