What is the cleanest lake in North Dakota?

Buffalo Lake in Pierce County is the cleanest lake on the readings in North Dakota with an EPA water-quality readings of — and 0.3 feet of water clarity.

How are these rankings calculated?

Nutrients and algae, total phosphorus, nitrogen, chlorophyll-a and turbidity, are read against EPA National Lakes Assessment 2022 condition classes for that lake’s ecoregion. Water clarity (Secchi depth) is measured and shown; it is not the letter. Lakes without enough recent samples are UNRATED, not given an F. Source data comes from the EPA Water Quality Portal.

Lakes With Algae Readings in North Dakota

29 lakes in North Dakota report elevated algae levels (chlorophyll-a above 20 µg/L). These lakes are most likely to develop blue-green algae blooms during warm, calm summer weather. Avoid swimming during visible blooms and rinse pets after contact.

Ranked List

#	Lake	County	Clarity	Phosphorus	Algae
1	Buffalo Lake	Pierce	—	0.3 ft	-	219.5 µg/L
2	Juanita Lake	Foster	—	1 ft	-	154.2 µg/L
3	Mchugh Slough Lake	Nelson	—	1.6 ft	416 µg/L	88.7 µg/L
4	Morrison Lake	Ramsey	—	1.9 ft	548.5 µg/L	85.9 µg/L
5	Kalmbach Lake	LaMoure	—	0.7 ft	-	73.8 µg/L
6	Sweetbriar Dam Lake	Morton	—	3 ft	353 µg/L	54 µg/L
7	Cedar Lake	Slope	—	1.3 ft	136.5 µg/L	53.4 µg/L
8	Harmon Lake	Morton	—	-	20 µg/L	48.5 µg/L
9	Antelope Lake	Pierce	—	3.5 ft	-	43.6 µg/L
10	Sprague Lake	Sargent	—	1.6 ft	-	43.4 µg/L
11	Eastern Stump Lake	Nelson	—	4.7 ft	148.5 µg/L	39.1 µg/L
12	East Stump Lake	Nelson	—	8.5 ft	-	37.9 µg/L
13	Froelich Dam Lake	Sioux	—	3.9 ft	311.5 µg/L	37.5 µg/L
14	Sweet Briar Dam-Mid Reservoir	Morton	—	3 ft	239.5 µg/L	36.9 µg/L
15	Western Stump Lake	Nelson	—	4.3 ft	165.5 µg/L	36.7 µg/L
16	Dead Colt Creek Dam Lake	Ransom	—	3.3 ft	-	32.3 µg/L
17	Mirror Lake	Adams	—	2.1 ft	388 µg/L	31.6 µg/L
18	Brewer Lake	Cass	—	4.3 ft	-	31.1 µg/L
19	Odland Dam Lake	Golden Valley	—	1.5 ft	135.5 µg/L	29.6 µg/L
20	Warsing Dam Lake	Eddy	—	2.3 ft	-	25.7 µg/L
21	Nygren Dam Lake	Morton	—	2.6 ft	73 µg/L	24.7 µg/L
22	Castle Rock Dam Lake	Hettinger	—	3.8 ft	148 µg/L	24.3 µg/L
23	Barnes Lake	Stutsman	—	6.4 ft	-	24 µg/L
24	Nelson Lake	Oliver	—	1.3 ft	275 µg/L	23.1 µg/L
25	Lake Laretta	Nelson	—	3.3 ft	253.5 µg/L	21.7 µg/L
26	Pelican Lake	Ramsey	—	3.7 ft	396 µg/L	21.2 µg/L
27	Epping-Springbrook Dam-Deepest Lake	Williams	—	4.9 ft	689.5 µg/L	20.4 µg/L
28	West Stump Lake	Nelson	—	9.8 ft	-	20.1 µg/L
29	Tioga Dam Lake	Williams	—	2.2 ft	182 µg/L	20 µg/L

Ranked List

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