Lake Ontario
Monroe County, New YorkView mapDirections
NY DEC publishes the water-quality measurements for Lake Ontario. Here is what has been measured.
- Limited data
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.
Lake Ontario is a lake in Monroe County, New York.
Source: EPA Water Quality Portal sampling records, NYSDEC, last sampled 2023-10-24. Methodology: how these readings are compared.
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. 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.
| 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 | 126µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 17.1µg/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. | 66 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
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Answers come straight from the public measurements and survey records on this page.
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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. 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.