Lake Ontario
Monroe County, New YorkView mapDirections
NY DEC publishes the water-quality measurements for Lake Ontario. Here is what has been measured.
- Impaired · Nutrients (phosphorus, nitrogen)
- Limited data
Ask about Lake Ontario
Answers come straight from the public measurements and survey records on this page.
Lake Ontario in Monroe County, New York has water-quality measurements published by NY DEC, shown here as reported. Phosphorus: 126 µg/L. Chlorophyll-a (algae): 17.1 µg/L.
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Lake Ontario is a lake in Monroe County, New York.
Source: EPA Water Quality Portal sampling records, NYSDEC, last sampled 2023-10-24. Grade methodology: LakeQuality methodology.
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Lake Ontario is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Lake Ontario is safe to swim in today is a call for the New York Department of Environmental Conservation and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Lake Ontario
These are the measurements NY DEC publishes for Lake Ontario, 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 126 µg/L. Chlorophyll-a 17.1 µg/L. TSI 66.
| Metric | Value | EPA condition class |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 126 µg/L | Measured, not scored |
| Chlorophyll-a (Algae) | 17.1 µg/L | Measured, not scored |
| Trophic State Index (TSI) | 66 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Fishing Lake Ontario
EPA Impairment Status
Lake Ontario is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit NY0301-0016 · Official waterbody report · Matched by proximity (0.98 km)
Nearby Lakes in Monroe County
Frequently asked questions about Lake Ontario
Where is Lake Ontario?
- Lake Ontario is a lake in Monroe County, New York. Its water-quality measurements are published by NY DEC and shown on this page as reported.
What is the water quality of Lake Ontario?
- Lake Ontario in Monroe County, New York has water-quality measurements published by NY DEC, shown here as reported. Phosphorus: 126 µg/L. Chlorophyll-a (algae): 17.1 µg/L.
Is Lake Ontario safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Lake Ontario is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
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Where this data comes from
15 measurements from 1 monitoring station, 2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- USGS New York Water Science Center
USGS-NY15 samples · 2023
Analytical methods
- P, wu, WCA, persulfate CF color
- Plant pigments, sonication & 445
- YSI EXO turbidity sensor, FNU
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