Broad Bay-Deep Spot Lake
Broad Bay-Deep Spot Lake in Carroll County, New Hampshire has a water quality grade of A (Excellent). Phosphorus: 6.8 µg/L. Chlorophyll-a (algae): 2.2 µg/L.
- Type
- Mesotrophic
Broad Bay-Deep Spot Lake is a mesotrophic lake in Carroll County, New Hampshire. Water quality is graded A based on 2 sampling years through 2025. Public access is available with 1 public boat landing. Compared to the 19 other monitored lakes in Carroll County, Broad Bay-Deep Spot Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2025-08-13. 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: 6.8 µg/L. Chlorophyll-a: 2.2 µg/L. Trophic State Index: 35.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 6.8 µg/L | Good |
| Chlorophyll-a (Algae) | 2.2 µg/L | Good |
| Trophic State Index (TSI) | 35 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Broad Bay-Deep Spot Lake
Compare lakeside cabins, hotels, and vacation rentals near Broad Bay-Deep Spot Lake in Carroll 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 Broad Bay-Deep Spot Lake
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Recreation & Access
- Lakefront Landing MarinaSemi-private
Named access points from the USGS National Boat Ramps inventory, snapped within 5 km. More lakes with boat ramps
Fishing Broad Bay-Deep Spot Lake
EPA Impairment Status
Broad Bay-Deep Spot Lake 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 NHLAK600020804-01-03 · Official waterbody report · Matched by proximity (0.39 km)
County Ranking
Ranked #1 of 20 lakes in Carroll County
Nearby Lakes in Carroll County
Frequently asked questions about Broad Bay-Deep Spot Lake
Where is Broad Bay-Deep Spot Lake?
- Broad Bay-Deep Spot Lake is a lake in Carroll 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 Broad Bay-Deep Spot Lake?
- Broad Bay-Deep Spot Lake in Carroll County, New Hampshire has a water quality grade of A (Excellent). Phosphorus: 6.8 µg/L. Chlorophyll-a (algae): 2.2 µg/L.
Is Broad Bay-Deep Spot Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Broad Bay-Deep Spot Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 2.2 µg/L. Always check local health department advisories before swimming.
Are there boat ramps on Broad Bay-Deep Spot Lake?
- Broad Bay-Deep Spot Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Lakefront Landing Marina.
Explore Broad Bay-Deep Spot Lake 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
Belknap County · Excellent
Strafford County · Excellent
Merrimack County · Excellent
Rockingham County · 24.6 ft
Grafton County · Excellent
Mesotrophic Lakes in New Hampshire
Where this data comes from
90 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)
1111330090 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
Named boat-access points from the USGS National Boat Ramps inventory