Mamanasco Lake
Fairfield County, Connecticut87 acresView mapDirections
CT DEEP publishes the water-quality measurements for Mamanasco Lake. Here is what has been measured.
- Impaired · Algal growth
- Public access
- Limited data
Mamanasco Lake in Fairfield County, Connecticut has water-quality measurements published by CT DEEP, shown here as reported. Phosphorus: 42 µg/L. Chlorophyll-a (algae): 15.1 µg/L. Surface area: 87 acres.
Mamanasco Lake is a 87-acre lake in Fairfield County, Connecticut. Limited fish-species data available. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2023-06-15. Methodology: how these readings are compared.
What Mamanasco Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming conditions
No readingRecreation use not supported
Nutrient and algae readings are not a swimming clearance. Mamanasco Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, nuisance exotic species. Check local advisories before you swim.
Whether Mamanasco Lake is safe to swim in today is a call for the Connecticut Department of Energy and Environmental Protection and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Mamanasco Lake
These are the measurements CT DEEP publishes for Mamanasco Lake, 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 42 µg/L. Chlorophyll-a 15.1 µg/L. TSI 58.
| 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 | 42µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 15.1µg/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. | 58 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Mamanasco Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
87 acres
Public access
Yes
Listed by CT DEEP
No bathymetric survey has been published for Mamanasco Lake, so its depth is not documented here.
Recreation & Access
- Mamanasco LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
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Stays near Mamanasco Lake
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Fishing Mamanasco Lake
Reservoir Info (USACE NID)
Mamanasco Lake is a man-made reservoir impounded by the Mamanasco Lake Dam (completed 1870), built primarily for recreation on the Titicus River Trib; earth-type dam, 6 ft tall and 120 ft long.
- Surface area
- 87 ac
- Normal storage
- 435 ac-ft
- Max storage
- 435 ac-ft
- Drainage area
- 0.59 sq mi
- Hazard class
- Significant
- Owner
- Camp, Jr.
Source: USACE National Inventory of Dams, NID ID CT00220 · Operator website
EPA Impairment Status
Mamanasco Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life, Recreation.
Source: EPA ATTAINS assessment unit CT8104-00-2-L5_01 · Official waterbody report
Nearby Lakes in Fairfield County
Frequently asked questions about Mamanasco Lake
Where is Mamanasco Lake?
- Mamanasco Lake is a lake in Fairfield County, Connecticut. Its water-quality measurements are published by CT DEEP and shown on this page as reported.
What is the water quality of Mamanasco Lake?
- Mamanasco Lake in Fairfield County, Connecticut has water-quality measurements published by CT DEEP, shown here as reported. Phosphorus: 42 µg/L. Chlorophyll-a (algae): 15.1 µg/L. Surface area: 87 acres.
Is Mamanasco Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Mamanasco Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, nuisance exotic species. Check local advisories before you swim.
Are there boat ramps on Mamanasco Lake?
- Mamanasco Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Mamanasco Lake. Public access is listed as yes.
Can I fish at Mamanasco Lake?
- Mamanasco Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Connecticut's fish and wildlife agency, so check its current regulations before you go.
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Where this data comes from
4 measurements from 1 monitoring station, 2023. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- Connecticut Department Of Energy And Environmental Protection
CT_DEP01_WQX4 samples · 2023
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)
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
Named boat-access points from the USGS National Boat Ramps inventory