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LakeQuality

Data Report · Updated August 2026

The State of Québec’s Lakes 2026

Of 1,018 monitored lakes in Québec, 92.8% earn a water-quality grade of A or B and 1.7% score D or F (average grade B). Lac Beauport is the cleanest;

1,018
Monitored lakes graded
B
Average grade
92.8%
Grade A or B
0%
On impaired list

Québec grade distribution

A
B
A: 604 (59.3%)B: 341 (33.5%)C: 56 (5.5%)D: 13 (1.3%)F: 4 (0.4%)

Cleanest lakes in Québec

Highest combined water-quality score, 2026.

  1. 1.ALac Beauport — La Jacques-Cartier County16.7 ft clarity · 5 µg/L P · 2 µg/L chl-a
  2. 2.ALac Raquette — Beauce-Sartigan County19.8 ft clarity · 5 µg/L P · 2 µg/L chl-a
  3. 3.ALac des Cornes — Antoine-Labelle County20.7 ft clarity · 3 µg/L P · 1 µg/L chl-a
  4. 4.ALac PéRodeau — Antoine-Labelle County22.3 ft clarity · 3 µg/L P · 1 µg/L chl-a
  5. 5.ALac Duhamel — Les Laurentides County29.2 ft clarity · 2 µg/L P · 1 µg/L chl-a
  6. 6.ALac Vert — Papineau County26.6 ft clarity · 4 µg/L P · 1 µg/L chl-a
  7. 7.ALac Farmer — Les Pays-d'en-Haut County19.0 ft clarity · 4 µg/L P · 2 µg/L chl-a
  8. 8.ALac des Trois Montagnes — Les Laurentides County23.6 ft clarity · 3 µg/L P · 1 µg/L chl-a
  9. 9.ALac ThéOdore — Les Pays-d'en-Haut County16.1 ft clarity · 6 µg/L P · 3 µg/L chl-a
  10. 10.ALac Ouareau — Matawinie County16.7 ft clarity · 3 µg/L P · 2 µg/L chl-a

Most-polluted lakes

Lowest combined water-quality score among monitored lakes.

  1. 1.FLac Saint-Charles — Bellechasse County1.0 ft clarity · 94 µg/L P · 70 µg/L chl-a
  2. 2.FPetit Lac Saint-FrançOis — Le Val-Saint-François County2.3 ft clarity · 161 µg/L P · 78 µg/L chl-a
  3. 3.FLac Bleu — Rouville County1.1 ft clarity · 165 µg/L P · 82 µg/L chl-a
  4. 4.DLac à Vaillancourt — Rimouski-Neigette County4.9 ft clarity · 64 µg/L P · 56 µg/L chl-a
  5. 5.DLac Roxton — La Haute-Yamaska County3.8 ft clarity · 57 µg/L P · 36 µg/L chl-a
  6. 6.DLac Macamic — Abitibi-Ouest County0.7 ft clarity · 104 µg/L P · 6 µg/L chl-a
  7. 7.DLac à la Truite — Les Appalaches County3.0 ft clarity · 64 µg/L P · 16 µg/L chl-a
  8. 8.DLac Waterloo — La Haute-Yamaska County4.3 ft clarity · 33 µg/L P · 21 µg/L chl-a
  9. 9.DLac Mandeville — D'Autray County3.9 ft clarity · 29 µg/L P · 34 µg/L chl-a
  10. 10.DLac Abitibi — Abitibi-Ouest County0.7 ft clarity · 70 µg/L P · 8 µg/L chl-a

Worst algae hotspots

Highest measured chlorophyll-a (algae) concentration.

  1. 1.FLac Bleu — Rouville County82 µg/L chlorophyll-a
  2. 2.FPetit Lac Saint-FrançOis — Le Val-Saint-François County78 µg/L chlorophyll-a
  3. 3.FLac Saint-Charles — Bellechasse County70 µg/L chlorophyll-a
  4. 4.DLac à Vaillancourt — Rimouski-Neigette County56 µg/L chlorophyll-a
  5. 5.DLac Roxton — La Haute-Yamaska County36 µg/L chlorophyll-a
  6. 6.DLac Mandeville — D'Autray County34 µg/L chlorophyll-a
  7. 7.DLac de la Belle Montagne — Matawinie County28 µg/L chlorophyll-a
  8. 8.DLac Lindsay — Coaticook County26 µg/L chlorophyll-a
  9. 9.DLac Aux Canards — Bellechasse County22 µg/L chlorophyll-a
  10. 10.CLac Pelletier — Abitibi-Témiscamingue County22 µg/L chlorophyll-a

Explore Québec lakes

Lake Fishing Forecast

Species activity outlook by water temperature and season

Grades combine Secchi clarity, total phosphorus, and chlorophyll-a from the EPA Water Quality Portal and state agencies. See the full methodology, the national State of America’s Lakes report, or all Québec lakes.

Cite this report: LakeQuality, “The State of Québec’s Lakes 2026,” lakequality.org/report/qc.