Lac Johnston
Les Collines-de-l'Outaouais, QuébecView mapDirections
This is MELCCFP's own trophic classification for 2025, not a LakeQuality grade. See every year
- 49 ft max depth
Lac Johnston in Les Collines-de-l'Outaouais, Québec is classified zone de transition oligo-mésotrophe by Ministère de l’Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs (Québec) for 2025. Water clarity: 3.7 m visibility. Phosphorus: 9.7 µg/L. Chlorophyll-a (algae): 3.1 µg/L.
Lac Johnston is a lake in Les Collines-de-l'Outaouais County, Québec with an estimated average depth of about 49 feet.
Source: Québec RSVL (MELCCFP) — not the EPA Water Quality Portal, last sampled 2025-08-01. Methodology: how these readings are compared.
What Lac Johnston is good for
From access and monitoring records, not editorial picks.
- Clear water12.1 ft of visibility
Swimming conditions
No readingNot rated
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Lac Johnston is safe to swim in today is a call for le Ministère de l'Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Lac Johnston
These are the measurements MELCCFP publishes for Lac Johnston, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 12.1 ft. Phosphorus 9.7 µg/L. Chlorophyll-a 3.1 µg/L.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3.7m | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 9.7µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 3.1µg/L | Measured, not scored The green pigment in algae — a direct measure of how much algae is in the water. |
Ask about Lac Johnston
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~14.9 m est.
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Québec has not published bathymetry for Lac Johnston.
Lake Size & Watershed
Watershed (drainage) area
5 sq mi
HydroLAKES / HydroSHEDS
Surface area
195 acres
HydroLAKES / HydroSHEDS
Shoreline
4.3 mi
HydroLAKES / HydroSHEDS
Elevation
495 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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Frequently asked questions about Lac Johnston
Where is Lac Johnston?
- Lac Johnston is a lake in Les Collines-de-l'Outaouais, Québec. MELCCFP classifies it zone de transition oligo-mésotrophe for 2025. This is MELCCFP's own trophic classification for 2025, not a LakeQuality grade.
What is the water quality of Lac Johnston?
- Lac Johnston in Les Collines-de-l'Outaouais, Québec is classified zone de transition oligo-mésotrophe by Ministère de l’Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs (Québec) for 2025. Water clarity: 3.7 m visibility. Phosphorus: 9.7 µg/L. Chlorophyll-a (algae): 3.1 µg/L.
Is Lac Johnston safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is Lac Johnston?
- No published bathymetric survey covers Lac Johnston, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 49 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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The authority’s own classification
Ministère de l’Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs (Québec) publishes its own classification for Lac Johnston. It is shown here as theirs, in their words, and is not folded into the LakeQuality letter.
This is MELCCFP's own trophic classification for 2025, not a LakeQuality grade.
A trophic class ranks how nutrient-rich a lake is, from oligotrophic at the low end to eutrophic at the high end. It describes nutrients and plant growth, not bacteria, and it is not a swimming clearance.
Earlier years (21 classified 2014–2025)
| Year | Published class |
|---|---|
| 2024 | classe mésotrophe |
| 2023 | zone de transition oligo-mésotrophe |
| 2022 | zone de transition oligo-mésotrophe |
| 2021 | zone de transition oligo-mésotrophe |
| 2020 | zone de transition oligo-mésotrophe |
| 2019 | zone de transition oligo-mésotrophe |
| 2018 | classe mésotrophe |
| 2017 | zone de transition oligo-mésotrophe |
| 2016 | zone de transition oligo-mésotrophe |
| 2015 | zone de transition oligo-mésotrophe |
| 2014 | classe mésotrophe |
Published by Ministère de l’Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs (Québec). A classification is not a same-day swimming clearance. See data sources.
Where this data comes from
Measurements for Lac Johnston come from the Réseau de surveillance volontaire des lacs (RSVL), not the EPA Water Quality Portal. Per-sample source details are not recorded for this lake. MELCCFP RSVL (CC BY 4.0). See data sources.
Other records on this page
Lake size & watershed from HydroLAKES (HydroSHEDS)