Northumberland County Lake Quality
Ontario, 3 lakes, average grade C (Fair)
Northumberland County has 3 graded lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. The county average is C — the middle of the rubric, with one or two lakes pulling the average up or down depending on year.
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. Little Lake (B) is the cleanest in the county.
Quick Answers for Northumberland County
Planning a trip? Check special fishing regulations for Little Lake — or check the official Ontario fishing regulations.
All Lakes in Northumberland County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Little Lake | B | 4.9 ft | 9.8 µg/L |
| 2 | Lake Seymour | C | 5.6 ft | 22.8 µg/L |
| 3 | Banister Pond | C | - | 54.4 µg/L |
Other Counties in Ontario
See how Northumberland 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 Northumberland County
Top-rated places to stay near Northumberland County
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a trip to Northumberland County?
Get lake water-quality report cards plus the best cabin & lodging deals near Northumberland County — straight to your inbox. No spam, unsubscribe anytime.
Source: EPA National Aquatic Resource Surveys, 2026.