Lake Quassapaug
Lake Quassapaug in New Haven County, Connecticut has a water quality grade of B (Good). Phosphorus: 15.5 µg/L. Chlorophyll-a (algae): 2.9 µg/L. Surface area: 290 acres.
- Area
- 290 acres
- Type
- Mesotrophic
Lake Quassapaug is a 290-acre mesotrophic lake in New Haven County, Connecticut. Water quality is graded B based on 2 sampling years through 2024. Compared to the 1 other monitored lakes in New Haven County, Lake Quassapaug ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2024-08-01. 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: 15.5 µg/L. Chlorophyll-a: 2.9 µg/L. Trophic State Index: 42.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 15.5 µg/L | Good |
| Chlorophyll-a (Algae) | 2.9 µg/L | Not graded |
| Trophic State Index (TSI) | 42 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Lake Quassapaug
Compare lakeside cabins, hotels, and vacation rentals near Lake Quassapaug in New Haven County, Connecticut — 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 Quassapaug
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Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 290 acres |
No bathymetric survey has been published for Lake Quassapaug, so its depth is not documented here.
Fishing Lake Quassapaug
Reservoir Info (USACE NID)
Lake Quassapaug is a man-made reservoir impounded by the Quassapaug Lake Dam (completed 1900), built primarily for recreation on the Eightmile Brook; earth-type dam, 24 ft tall and 125 ft long.
- Surface area
- 290 ac
- Normal storage
- 2,601 ac-ft
- Drainage area
- 1.82 sq mi
- Hazard class
- Significant
- Owner
- West Shore Owners Association
Source: USACE National Inventory of Dams, NID ID CT00329 · Operator website
County Ranking
Ranked #1 of 2 lakes in New Haven County
Nearby Lakes in New Haven County
Frequently asked questions about Lake Quassapaug
Where is Lake Quassapaug?
- Lake Quassapaug is a lake in New Haven County, Connecticut. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Lake Quassapaug?
- Lake Quassapaug in New Haven County, Connecticut has a water quality grade of B (Good). Phosphorus: 15.5 µg/L. Chlorophyll-a (algae): 2.9 µg/L. Surface area: 290 acres.
Is Lake Quassapaug safe to swim in?
- Good for swimming, clear water with low algae levels. Lake Quassapaug has a water quality grade of B (Good). Algae concentration (chlorophyll-a) is 2.9 µg/L. Always check local health department advisories before swimming.
Explore Lake Quassapaug across LakeGrade
More Connecticut Lake Rankings
Other Grade B Lakes in Connecticut
Mesotrophic Lakes in Connecticut
Where this data comes from
40 measurements from 1 monitoring station, 2021–2024. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- Connecticut Department Of Energy And Environmental Protection
CT_DEP01_WQX40 samples · 2021–2024
Analytical methods
- Total Phosphorus After Block Digestion
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- Nitrate-Nitrite Nitrogen by Colorimetry
- Turbidity by Nephelometry
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.