Leeds and Grenville Counties County Lake Quality
Ontario, 34 lakes, average grade B (Good)
There are 34 graded lakes in Leeds and Grenville Counties County. The mix is varied enough that the county-level average tells you the broad strokes, not the choose-this-cabin specifics. The county-wide average lands at B — solid water quality with most lakes carrying clear summer transparency and low-to-moderate phosphorus.
The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Crosby Lake (A); the most-stressed is Little Cranberry Lake (C).
Quick Answers for Leeds and Grenville Counties County
Planning a trip? Check special fishing regulations for Crosby Lake — or check the official Ontario fishing regulations.
All Lakes in Leeds and Grenville Counties County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Crosby Lake | A | 17.1 ft | 9.9 µg/L |
| 2 | Bass Lake | A | 19.4 ft | 13.9 µg/L |
| 3 | Bass Lake | A | 19 ft | 6.3 µg/L |
| 4 | Big Rideau Lake | A | 18.9 ft | 9.7 µg/L |
| 5 | Charleston Lake | A | 19.7 ft | 9.6 µg/L |
| 6 | Higley Lake | A | 15.4 ft | 11.2 µg/L |
| 7 | Indian Lake | A | 15.7 ft | 12.6 µg/L |
| 8 | Otter Lake | A | 14.9 ft | 9.3 µg/L |
| 9 | Sand Lake | A | 16.4 ft | 13.6 µg/L |
| 10 | St Lawrence River Lake | A | 31.2 ft | 10.1 µg/L |
| 11 | Mill Pond | A | - | 17.3 µg/L |
| 12 | Benson Lake | A | 10.2 ft | 14.1 µg/L |
| 13 | Clear Lake | A | 14.6 ft | 13.9 µg/L |
| 14 | Gananoque Lake | A | 10.5 ft | 19.5 µg/L |
| 15 | Gananoque River Lake | A | 10.5 ft | 17.5 µg/L |
| 16 | Grippen Lake | A | 13.1 ft | 11.8 µg/L |
| 17 | Long Lake | A | 10.2 ft | 13.7 µg/L |
| 18 | Newboro Lake | A | 14.8 ft | 17 µg/L |
| 19 | Red Horse Lake | A | 13.1 ft | 17.6 µg/L |
| 20 | Tommy Lake | A | 11.6 ft | 19.5 µg/L |
| 21 | Whitefish Lake | A | 12.1 ft | 14.7 µg/L |
| 22 | Graham Lake | B | 8.2 ft | 13 µg/L |
| 23 | Little Crosby Lake | B | 9.5 ft | 9.4 µg/L |
| 24 | Loon Lake | B | 13.1 ft | - |
| 25 | Lower Beverley Lake | B | 9.8 ft | 18.8 µg/L |
| 26 | Singleton Lake | B | 8.9 ft | 18.5 µg/L |
| 27 | Upper Beverley Lake | B | 8.5 ft | 18.3 µg/L |
| 28 | Upper Rideau Lake | B | 12.5 ft | 20 µg/L |
| 29 | Killenbeck Lake | B | 7.9 ft | 21.8 µg/L |
| 30 | Lyndhurst Lake | B | 9.8 ft | 24.7 µg/L |
| 31 | Temperance Lake | B | 5.9 ft | 17.9 µg/L |
| 32 | Little Cranberry Lake | C | 8.2 ft | 44.7 µg/L |
| 33 | South Lake | C | 4.9 ft | 26.1 µg/L |
| 34 | Troy Lake | C | 5.6 ft | 24 µg/L |
Other Counties in Ontario
See how Leeds and Grenville Counties County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 38 states.
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Source: EPA National Aquatic Resource Surveys, 2026.