Thirty Island Lake
Frontenac, OntarioView mapDirections
Ontario MECP publishes the water-quality measurements for Thirty Island Lake. Here is what has been measured.
- 50 ft max depth
Thirty Island Lake in Frontenac, Ontario has water-quality measurements published by Ontario MECP, shown here as reported. Water clarity: 5.7 m visibility. Phosphorus: 10.5 µg/L.
Thirty Island Lake is a lake in Frontenac County, Ontario with an estimated average depth of about 50 feet.
Source: Ontario open-data programmes (Lake Partner Program and Broad-scale Monitoring) — not the EPA Water Quality Portal, last sampled 2025-10-06. Methodology: how these readings are compared.
What Thirty Island Lake is good for
From access and monitoring records, not editorial picks.
- Clear water18.7 ft of visibility
Swimming conditions
No readingNot rated
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Thirty Island Lake is safe to swim in today is a call for the Ontario Ministry of the Environment, Conservation and Parks and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Thirty Island Lake
These are the measurements Ontario MECP publishes for Thirty Island Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Crystal clear, you can see 18.7 ft down. Phosphorus 10.5 µg/L. TSI 36.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 5.7m | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 10.5µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | No reading 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. | 36 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Thirty Island Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~15.2 m est.
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Ontario has not published bathymetry for Thirty Island Lake.
Lake Size & Watershed
Watershed (drainage) area
6 sq mi
HydroLAKES / HydroSHEDS
Surface area
512 acres
HydroLAKES / HydroSHEDS
Shoreline
11 mi
HydroLAKES / HydroSHEDS
Elevation
515 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
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Stays near Thirty Island Lake
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Fishing Thirty Island Lake
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Frequently asked questions about Thirty Island Lake
Where is Thirty Island Lake?
- Thirty Island Lake is a lake in Frontenac, Ontario. Its water-quality measurements are published by Ontario MECP and shown on this page as reported.
What is the water quality of Thirty Island Lake?
- Thirty Island Lake in Frontenac, Ontario has water-quality measurements published by Ontario MECP, shown here as reported. Water clarity: 5.7 m visibility. Phosphorus: 10.5 µg/L.
Is Thirty Island Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is Thirty Island Lake?
- No published bathymetric survey covers Thirty Island Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 50 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
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Where this data comes from
Measurements for Thirty Island Lake come from Ontario open-data programmes (Lake Partner Program and Broad-scale Monitoring), not the EPA Water Quality Portal. Per-sample source details are not recorded for this lake. Contains information licensed under the Open Government Licence – Ontario. See data sources.
Other records on this page
Lake size & watershed from HydroLAKES (HydroSHEDS)