Morton County Lake Quality
North Dakota, 4 lakes, average grade F (Very Poor)
Only 4 lakes in Morton 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. The county average is F — the most-stressed bracket in our rubric. Most monitored lakes here show persistent nutrient loading and algal pressure.
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 Nygren Dam Lake (D); the most-stressed is Sweetbriar Dam Lake (F).
Quick Answers for Morton County
Planning a trip? Check special fishing regulations for Nygren Dam Lake, whether the fish are safe to eat, and the best times to fish — or check the official North Dakota fishing regulations.
Fishing in Morton County
All Lakes in Morton County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Nygren Dam Lake | D | 2.6 ft | 35.5 ft | - |
| 2 | Sweetbriar Dam Lake | F | 3 ft | 29.9 ft | - |
| 3 | Sweet Briar Dam-Mid Reservoir | F | 3 ft | 29.9 ft | - |
| 4 | Harmon Lake | F | - | 46.8 ft | - |
Other Counties in North Dakota
See how Morton County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 15 states.
Where to stay near Morton County
Top-rated places to stay near Morton 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 Morton County?
Get lake water-quality report cards plus the best cabin & lodging deals near Morton County — straight to your inbox. No spam, unsubscribe anytime.
Source: EPA National Aquatic Resource Surveys, 2026.