Hypereutrophic Lakes in North Dakota
15 hypereutrophic lakes in North Dakota. Very high nutrients, dense algae, poor clarity.
Hypereutrophic lakes (TSI above 70) are at the upper end of the productivity scale: visible algal blooms most weeks of summer, clarity often under 3 feet, and meaningful risk of harmful-algal-bloom toxin events. 15 hypereutrophic lakes are on the North Dakota books. Almost none of them are deep — 0% break 50 feet. Shallow basin plus heavy nutrient input is the consistent recipe.
Hypereutrophic lakes carry the highest phosphorus and chlorophyll-a readings on record; the trophic class and the readings are measuring closely related dimensions of the same underlying nutrient regime.
| # | Lake | County | Clarity | Depth | TSI |
|---|---|---|---|---|---|
| 1 | Nelson Lake | Oliver | 1.3 ft | - | 73 |
| 2 | Cedar Lake | Slope | 1.3 ft | - | 73 |
| 3 | Froelich Dam Lake | Sioux | 3.9 ft | - | 70 |
| 4 | Odland Dam Lake | Golden Valley | 1.5 ft | - | 70 |
| 5 | Stanley Reservoir | Mountrail | 1.1 ft | - | 75 |
| 6 | Western Stump Lake | Nelson | 4.3 ft | - | 67 |
| 7 | Morrison Lake | Ramsey | 1.9 ft | - | 79 |
| 8 | Eastern Stump Lake | Nelson | 4.7 ft | - | 66 |
| 9 | Mchugh Slough Lake | Nelson | 1.6 ft | - | 79 |
| 10 | Buffalo Lake | Pierce | 0.3 ft | - | 88 |
| 11 | Antelope Lake | Pierce | 3.5 ft | - | 63 |
| 12 | Sweetbriar Dam Lake | Morton | 3 ft | - | 73 |
| 13 | Sweet Briar Dam-Mid Reservoir | Morton | 3 ft | - | 70 |
| 14 | Mirror Lake | Adams | 2.1 ft | - | 74 |
| 15 | Harmon Lake | Morton | - | - | 58 |
All hypereutrophic lakes →Minnesota version →Wisconsin version →Illinois version →Michigan version →Iowa version →Ohio version →Pennsylvania version →New York version →Missouri version →Indiana version →South Dakota version →Florida version →Colorado version →North Carolina version →Vermont version →Texas version →Oregon version →Arkansas version →Oklahoma version →Kansas version →Nebraska version →Nevada version →Arizona version →Idaho version →Montana version →New Mexico version →Tennessee version →Alabama version →Virginia version →Kentucky version →Utah version →Washington version →Wyoming version →Georgia version →Massachusetts version →Ontario version →Québec version →Nova Scotia version →British Columbia version →Newfoundland and Labrador version →All North Dakota lakes →
Source: EPA National Aquatic Resource Surveys, 2026.