Lake Katherine-Deep Spot
Grafton County, New Hampshire315 acresView mapDirections
NHDES publishes the water-quality measurements for Lake Katherine-Deep Spot. Here is what has been measured.
- Mesotrophic
- Impaired · Mercury
- Limited data
Lake Katherine-Deep Spot in Grafton County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 7.6 µg/L. Chlorophyll-a (algae): 10.7 µg/L. Surface area: 315 acres.
Lake Katherine-Deep Spot is a 315-acre mesotrophic lake in Grafton County, New Hampshire. Compared to the 26 other monitored lakes in Grafton County, Lake Katherine-Deep Spot ranks #19 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2024-06-13. Methodology: how these readings are compared.
Swimming conditions
Readings onlyLimited data
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. Lake Katherine-Deep Spot is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Lake Katherine-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 Lake Katherine-Deep Spot
These are the measurements NHDES publishes for Lake Katherine-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 7.6 µg/L. Chlorophyll-a 10.7 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 | 7.6µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 10.7µg/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 Lake Katherine-Deep Spot
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
315 acres
No bathymetric survey has been published for Lake Katherine-Deep Spot, so its depth is not documented here.
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Stays near Lake Katherine-Deep Spot
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Fishing Lake Katherine-Deep Spot
Reservoir Info (USACE NID)
Lake Katherine-Deep Spot is a man-made reservoir impounded by the Lake Tarleton Dam (completed 1800), built primarily for recreation on the Eastman Brook; concrete-type dam, 8 ft tall and 200 ft long.
- Surface area
- 315 ac
- Normal storage
- 416 ac-ft
- Max storage
- 1,418 ac-ft
- Drainage area
- 7.09 sq mi
- Hazard class
- Low
- Owner
- DALEY ENERGY LLC
Source: USACE National Inventory of Dams, NID ID NH00556 · Operator website · Matched by proximity (0.6 km)
EPA Impairment Status
Lake Katherine-Deep Spot 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: Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NHLAK801040201-02 · Official waterbody report
Nearby Lakes in Grafton County
Frequently asked questions about Lake Katherine-Deep Spot
Where is Lake Katherine-Deep Spot?
- Lake Katherine-Deep Spot is a lake in Grafton County, New Hampshire. Its water-quality measurements are published by NHDES and shown on this page as reported.
What is the water quality of Lake Katherine-Deep Spot?
- Lake Katherine-Deep Spot in Grafton County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 7.6 µg/L. Chlorophyll-a (algae): 10.7 µg/L. Surface area: 315 acres.
Is Lake Katherine-Deep Spot safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Lake Katherine-Deep Spot is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Explore Lake Katherine-Deep Spot across LakeQuality
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Where this data comes from
7 measurements from 1 monitoring station, 2021–2024. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- New Hampshire Department Of Environmental Services (BEACH)
111133007 samples · 2021–2024
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