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 overwhelmingly grade D or F — the trophic class and the grade are measuring closely-related dimensions of the same underlying nutrient regime.

#	Lake	County	Grade	Clarity	Depth	TSI
1	Nelson Lake	Oliver	C	1.3 ft	-	73
2	Cedar Lake	Slope	C	1.3 ft	-	73
3	Froelich Dam Lake	Sioux	D	3.9 ft	-	70
4	Odland Dam Lake	Golden Valley	D	1.5 ft	-	70
5	Stanley Reservoir	Mountrail	D	1.1 ft	-	75
6	Western Stump Lake	Nelson	F	4.3 ft	-	67
7	Morrison Lake	Ramsey	F	1.9 ft	-	79
8	Eastern Stump Lake	Nelson	F	4.7 ft	-	66
9	Mchugh Slough Lake	Nelson	F	1.6 ft	-	79
10	Buffalo Lake	Pierce	F	0.3 ft	-	88
11	Antelope Lake	Pierce	F	3.5 ft	-	63
12	Sweetbriar Dam Lake	Morton	F	3 ft	-	73
13	Sweet Briar Dam-Mid Reservoir	Morton	F	3 ft	-	70
14	Mirror Lake	Adams	F	2.1 ft	-	74
15	Harmon Lake	Morton	F	-	-	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 →All North Dakota lakes →

Source: EPA National Aquatic Resource Surveys, 2026.