Eastern Ontario County Lake Quality
Ontario, 5 lakes, average grade C (Fair)
Only 5 lakes in Eastern Ontario County carry an active grade. The county-level summary is therefore representative of those specific lakes, not necessarily of every water body in the county. Eastern Ontario County averages to a C. The distribution behind that average matters more than the letter: a few stressed lakes versus many decent ones can produce the same average as the inverse.
Most of the county's monitored lakes are shallow — under 50 feet — which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed. Greely Lakes (B) is the cleanest in the county.
Quick Answers for Eastern Ontario County
Planning a trip? Check special fishing regulations for Greely Lakes — or check the official Ontario fishing regulations.
All Lakes in Eastern Ontario County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Greely Lakes | B | 6.9 ft | 20.5 µg/L |
| 2 | Lac Deschenes Lake | B | 5.9 ft | 15.3 µg/L |
| 3 | Mackay Lake | C | 9.8 ft | - |
| 4 | Water'S Edge Lake | C | 3.9 ft | 36 µg/L |
| 5 | Colonel by Lake | D | 1.6 ft | 44.1 µg/L |
Other Counties in Ontario
See how Eastern Ontario County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 38 states.
Where to stay near Eastern Ontario County
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Source: EPA National Aquatic Resource Surveys, 2026.