Lake Katherine-Deep Spot
Lake Katherine-Deep Spot in Grafton County, New Hampshire has a water quality grade of B (Good). Phosphorus: 7.6 µg/L. Chlorophyll-a (algae): 10.7 µg/L. Surface area: 315 acres.
- Area
- 315 acres
- Type
- Mesotrophic
Lake Katherine-Deep Spot is a 315-acre mesotrophic lake in Grafton County, New Hampshire. Water quality is graded B based on 1 sampling years through 2024. 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. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Good for swimming, clear water with low algae levels
Water Quality Grade: B (Good)
No clarity data. Phosphorus level: 7.6 µg/L. Chlorophyll-a: 10.7 µg/L. Trophic State Index: 44.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 7.6 µg/L | Good |
| Chlorophyll-a (Algae) | 10.7 µg/L | Not graded |
| Trophic State Index (TSI) | 44 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Lake Katherine-Deep Spot
Compare lakeside cabins, hotels, and vacation rentals near Lake Katherine-Deep Spot in Grafton County, New Hampshire — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Lake Katherine-Deep Spot
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Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 315 acres |
No bathymetric survey has been published for Lake Katherine-Deep Spot, so its depth is not documented here.
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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NHLAK801040201-02 · Official waterbody report · Matched by proximity (0.11 km)
County Ranking
Ranked #19 of 27 lakes in Grafton County
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. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Lake Katherine-Deep Spot?
- Lake Katherine-Deep Spot in Grafton County, New Hampshire has a water quality grade of B (Good). 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?
- Good for swimming, clear water with low algae levels. Lake Katherine-Deep Spot has a water quality grade of B (Good). Algae concentration (chlorophyll-a) is 10.7 µg/L. Always check local health department advisories before swimming.
Explore Lake Katherine-Deep Spot across LakeGrade
More New Hampshire Lake Rankings
Top 25 by overall water quality score
Top 25 by Secchi water clarity
Grade A/B + low algae filter
Panfish-rich, public access
Full state directory
Other Grade B Lakes in New Hampshire
Mesotrophic Lakes in New Hampshire
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)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database