Highland Lake-Deep Spot
Highland Lake-Deep Spot in Merrimack County, New Hampshire has a water quality grade of A (Excellent). Phosphorus: 13.1 µg/L. Chlorophyll-a (algae): 3.5 µg/L. Surface area: 210 acres.
- Area
- 210 acres
- Type
- Mesotrophic
Highland Lake-Deep Spot is a 210-acre mesotrophic lake in Merrimack County, New Hampshire. Water quality is graded A based on 2 sampling years through 2025. Compared to the 40 other monitored lakes in Merrimack County, Highland Lake-Deep Spot ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2025-09-18. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLow algae
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.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
No clarity data. Phosphorus level: 13.1 µg/L. Chlorophyll-a: 3.5 µg/L. Trophic State Index: 42.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 13.1 µg/L | Good |
| Chlorophyll-a (Algae) | 3.5 µg/L | Good |
| Trophic State Index (TSI) | 42 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Highland Lake-Deep Spot
Compare lakeside cabins, hotels, and vacation rentals near Highland Lake-Deep Spot in Merrimack 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 Highland Lake-Deep Spot
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Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 210 acres |
No bathymetric survey has been published for Highland Lake-Deep Spot, so its depth is not documented here.
Fishing Highland Lake-Deep Spot
Reservoir Info (USACE NID)
Highland Lake-Deep Spot is a man-made reservoir impounded by the Highland Lake Dam (completed 1935), built primarily for recreation on the Tr Sucker Brook; earth-type dam, 10 ft tall and 180 ft long.
- Surface area
- 210 ac
- Normal storage
- 440 ac-ft
- Max storage
- 1,050 ac-ft
- Drainage area
- 5.02 sq mi
- Hazard class
- Significant
- Owner
- TOWN OF ANDOVER
Source: USACE National Inventory of Dams, NID ID NH00035 · Operator website · Matched by proximity (0.88 km)
EPA Impairment Status
Highland Lake-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 NHLAK700010804-01-01 · Official waterbody report · Matched by proximity (0.31 km)
County Ranking
Ranked #2 of 41 lakes in Merrimack County
Nearby Lakes in Merrimack County
Frequently asked questions about Highland Lake-Deep Spot
Where is Highland Lake-Deep Spot?
- Highland Lake-Deep Spot is a lake in Merrimack County, New Hampshire. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Highland Lake-Deep Spot?
- Highland Lake-Deep Spot in Merrimack County, New Hampshire has a water quality grade of A (Excellent). Phosphorus: 13.1 µg/L. Chlorophyll-a (algae): 3.5 µg/L. Surface area: 210 acres.
Is Highland Lake-Deep Spot safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Highland Lake-Deep Spot has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 3.5 µg/L. Always check local health department advisories before swimming.
Explore Highland Lake-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 A Lakes in New Hampshire
Belknap County · Excellent
Grafton County · Excellent
Grafton County · Excellent
Belknap County · Excellent
Sullivan County · Excellent
Sullivan County · Excellent
Mesotrophic Lakes in New Hampshire
Where this data comes from
42 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)
1111330042 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)
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