Obrien Lake
Lanark, OntarioView mapDirections
Ontario MECP publishes the water-quality measurements for Obrien Lake. Here is what has been measured.
- 42 ft max depth
Obrien Lake in Lanark, Ontario has water-quality measurements published by Ontario MECP, shown here as reported. Water clarity: 5 m visibility. Phosphorus: 8.8 µg/L.
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Obrien Lake is a lake in Lanark County, Ontario with an estimated average depth of about 42 feet.
Source: Ontario open-data programmes (Lake Partner Program and Broad-scale Monitoring) — not the EPA Water Quality Portal, last sampled 2016-05-25. Grade methodology: LakeQuality methodology.
What Obrien Lake is good for
From access and monitoring records, not editorial picks.
- Clear water16.2 ft of visibility
Swimming conditions
No readingNot rated
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Obrien 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 Obrien Lake
These are the measurements Ontario MECP publishes for Obrien 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 16.2 ft down. Phosphorus 8.8 µg/L. TSI 36.
| Metric | Value | EPA condition class |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.95 m | Measured, not scored |
| Phosphorus | 8.8 µg/L | Measured, not scored |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 36 | Oligotrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~12.8 m est. |
| Average Depth | ~3.7 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 Obrien Lake.
Lake Size & Watershed
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.
Fishing Obrien Lake
Nearby Lakes in Lanark
Frequently asked questions about Obrien Lake
Ask about Obrien Lake
Answers come straight from the public measurements and survey records on this page.
Where is Obrien Lake?
- Obrien Lake is a lake in Lanark, Ontario. Its water-quality measurements are published by Ontario MECP and shown on this page as reported.
What is the water quality of Obrien Lake?
- Obrien Lake in Lanark, Ontario has water-quality measurements published by Ontario MECP, shown here as reported. Water clarity: 5 m visibility. Phosphorus: 8.8 µg/L.
Is Obrien Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is Obrien Lake?
- No published bathymetric survey covers Obrien Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 42 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 Obrien 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)