What is the cleanest lake in Minnesota?

Rainy Lake in Cass County has the cleanest nutrient and algae readings in Minnesota, with 13.9 feet of measured 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 separately. Lakes without enough recent samples are listed without a condition class rather than ranked low. Source data comes from the EPA Water Quality Portal.

Cleanest Lakes in Minnesota

Rainy Lake in Cass County leads the rankings on measured clarity and nutrients and 13.9 ft of clarity. Below are the top 50 cleanest monitored lakes in Minnesota, ranked on EPA nutrient and algae measurements.

Ranked List

#	Lake	County	Clarity	Phosphorus	Algae
1	Rainy Lake	Cass	13.9 ft	11.5 µg/L	1.8 µg/L
2	Crane Lake	Otter Tail	9 ft	15 µg/L	6.4 µg/L
3	Lobster Lake	Douglas	13 ft	20.5 µg/L	3.6 µg/L
4	East Fox Lake	Crow Wing	16.4 ft	10 µg/L	2.7 µg/L
5	Deep Portage Lake	Cass	15.4 ft	9 µg/L	1.6 µg/L
6	Clearwater Lake	Cook	29 ft	4 µg/L	1.3 µg/L
7	Clearwater Lake	Wright	9.8 ft	22 µg/L	6.3 µg/L
8	Clearwater Lake	Clearwater	10 ft	16 µg/L	3.2 µg/L
9	Lower Hay Lake	Crow Wing	18.5 ft	13 µg/L	2.7 µg/L
10	Latoka Lake	Douglas	19 ft	11 µg/L	2.2 µg/L
11	Little Birch Lake	Todd	13 ft	19 µg/L	3.1 µg/L
12	North Long Lake	Crow Wing	15.1 ft	14 µg/L	2.7 µg/L
13	Bad Medicine Lake	Becker	25 ft	6 µg/L	1.6 µg/L
14	Mud Lake	Becker	12.5 ft	22 µg/L	5.9 µg/L
15	Big Lake	Beltrami	9.7 ft	15 µg/L	4.8 µg/L
16	Big Lake	Carlton	10 ft	13.5 µg/L	3.2 µg/L
17	Big Lake	Sherburne	13.6 ft	10.5 µg/L	6.1 µg/L
18	Big Sugar Bush Lake	Becker	16.5 ft	10 µg/L	2.7 µg/L
19	Pelican Lake	Otter Tail	16.4 ft	15 µg/L	3 µg/L
20	Pelican Lake	Crow Wing	14.3 ft	11 µg/L	2.7 µg/L
21	Fullers Lake	Beltrami	15 ft	10 µg/L	2.4 µg/L
22	Birch Lake	Ramsey	5.9 ft	21 µg/L	3.3 µg/L
23	Birch Lake	Wright	15 ft	17 µg/L	4 µg/L
24	Birch Lake	Cass	14 ft	12 µg/L	4 µg/L
25	Round Lake	Aitkin	14.5 ft	10 µg/L	2.7 µg/L
26	Round Lake	Crow Wing	13.5 ft	17 µg/L	2.7 µg/L
27	Round Lake	Beltrami	18 ft	7 µg/L	1.9 µg/L
28	Round Lake	Otter Tail	11.2 ft	19 µg/L	4.8 µg/L
29	Round Lake	Anoka	8.9 ft	19 µg/L	5.3 µg/L
30	Ada Lake	Cass	14 ft	10 µg/L	2.7 µg/L
31	Pike Lake	Cook	17.4 ft	7 µg/L	2.6 µg/L
32	Whitefish Lake	Crow Wing	14.4 ft	14 µg/L	2.7 µg/L
33	Horseshoe Lake	Crow Wing	14.4 ft	11 µg/L	3.5 µg/L
34	Horseshoe Lake	Isanti	3.5 ft	13 µg/L	2.7 µg/L
35	Farm Lake	Lake	5.5 ft	15 µg/L	4.7 µg/L
36	Washburn Lake	Cass	14.1 ft	11 µg/L	3.7 µg/L
37	Long Lake	Stearns	13.5 ft	19 µg/L	4.4 µg/L
38	Long Lake	Kandiyohi	10.5 ft	13 µg/L	4.5 µg/L
39	Long Lake	Clearwater	20.5 ft	7 µg/L	1.4 µg/L
40	Long Lake	Cass	21.5 ft	9 µg/L	3 µg/L
41	Long Lake	Beltrami	20 ft	7 µg/L	1.8 µg/L
42	Long Lake	Otter Tail	12.3 ft	20 µg/L	4.4 µg/L
43	Long Lake	Becker	19.5 ft	8 µg/L	2.7 µg/L
44	Long Lake	Hubbard	11.2 ft	10 µg/L	4.5 µg/L
45	Long Lake	Otter Tail	12.1 ft	19.5 µg/L	5.3 µg/L
46	Long Lake	Beltrami	10 ft	17 µg/L	4.9 µg/L
47	Long Lake	Otter Tail	11.6 ft	17 µg/L	3.9 µg/L
48	Long Lake	Beltrami	14 ft	8 µg/L	1.9 µg/L
49	Dead Lake	Otter Tail	10.2 ft	20 µg/L	5.8 µg/L
50	Unnamed Lake	Crow Wing	6.6 ft	22 µg/L	3.6 µg/L

Ranked List

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