Oligotrophic Lakes in Minnesota

463 oligotrophic lakes in Minnesota. Low nutrients, clear water, excellent for swimming.

Oligotrophic lakes are the clear, cold, nutrient-poor end of the trophic scale. The Carlson Trophic State Index measures this as TSI below 40 — water transparent enough to see 15+ feet down, total phosphorus under 12 µg/L, chlorophyll-a barely registering. Across Minnesota, 463 lakes register as oligotrophic — 0% of them break 50 feet of depth, which is the structural condition that underwrites the trophic class. Without depth and a low-nutrient watershed, oligotrophy is hard to sustain.

On the LakeGrade rubric, oligotrophic lakes almost always pull an A or B — the same low-nutrient conditions that produce the trophic class also produce the high grade.

#	Lake	County	Grade	Clarity	Depth	TSI
1	East Fox Lake	Crow Wing	A	16.1 ft	-	37
2	Deep Portage Lake	Cass	A	15.4 ft	-	38
3	Little Wabana Lake	Itasca	A	23.8 ft	-	31
4	Clearwater Lake	Cook	A	30 ft	-	26
5	Clearwater Lake	Lake	A	18 ft	-	35
6	Lower Hay Lake	Crow Wing	A	19 ft	-	38
7	Latoka Lake	Douglas	A	19 ft	-	37
8	Bad Medicine Lake	Becker	A	25 ft	-	30
9	Big Sugar Bush Lake	Becker	A	17 ft	-	37
10	Fullers Lake: East Basin	Beltrami	A	15 ft	-	37
11	Birch Lake	Cook	A	18 ft	-	35
12	Birch Lake	Unknown	A	15 ft	-	38
13	Round Lake	Aitkin	A	15.3 ft	-	38
14	Round Lake	Cook	A	16.5 ft	-	36
15	Round Lake	Beltrami	A	18 ft	-	34
16	Pike Lake	Cook	A	17.8 ft	-	33
17	Pike Lake	St. Louis	A	18 ft	-	35
18	Horseshoe Lake	Cass	A	21 ft	-	33
19	Long Lake	Clearwater	A	20 ft	-	33
20	Long Lake	Cass	A	21.5 ft	-	34
21	Long Lake	Beltrami	A	20 ft	-	33
22	Long Lake	Becker	A	20 ft	-	34
23	Long Lake	Cass	A	16.8 ft	-	36
24	Long Lake	Itasca	A	16.7 ft	-	35
25	Long Lake	Itasca	A	16.9 ft	-	37
26	Dead Lake	Hubbard	A	16 ft	-	37
27	Unnamed Lake	Otter Tail	A	15.1 ft	-	37
28	Maple Lake	Itasca	A	15.3 ft	-	38
29	West Twin Lake	Crow Wing	A	19.8 ft	-	34
30	Sunshine Lake	St. Louis	A	20 ft	-	34
31	Shallow Lake	Itasca	A	16.4 ft	-	36
32	Trout Lake	Itasca	A	15.5 ft	-	38
33	Trout Lake	Itasca	A	18 ft	-	29
34	Trout Lake	Cook	A	19 ft	-	35
35	Otter Lake	Otter Tail	A	18 ft	-	35
36	Eddy Lake	Lake	A	16.5 ft	-	37
37	Cowdry Lake	Douglas	A	17 ft	-	40
38	Ossawinnamakee Lake	Crow Wing	A	20 ft	-	36
39	Clear Lake	Crow Wing	A	18 ft	-	34
40	Clear Lake	Aitkin	A	16 ft	-	37
41	Clear Lake	Itasca	A	14.9 ft	-	37
42	Bear Lake	Lake	A	17.4 ft	-	36
43	Blue Lake	Hubbard	A	17.4 ft	-	34
44	Blue Lake	Crow Wing	A	19 ft	-	35
45	Eagle Lake	Otter Tail	A	22.6 ft	-	30
46	West Fox Lake	Crow Wing	A	15 ft	-	39
47	Spearhead Lake	Hubbard	A	15 ft	-	38
48	Ida Lake	Douglas	A	16.5 ft	-	39
49	Star Lake	Crow Wing	A	19 ft	-	37
50	Star Lake	Otter Tail	A	16.7 ft	-	39
51	Upper Maple Lake	Wright	A	18 ft	-	40
52	Partridge Lake	Crow Wing	A	16.2 ft	-	37
53	Fish Lake	Otter Tail	A	17.8 ft	-	38
54	Sand Lake	Cass	A	21 ft	-	33
55	Jenny Lake	Lake	A	15.5 ft	-	38
56	Roger Lake	Crow Wing	A	16 ft	-	37
57	Hamlet Lake	Crow Wing	A	18.5 ft	-	35
58	Square Lake	Washington	A	17 ft	-	35
59	Tofte Lake	Lake	A	18.5 ft	-	35
60	Andrusia Lake	Beltrami	A	15.5 ft	-	40
61	Green Lake	Beltrami	A	18.5 ft	-	34
62	Girl Lake	Cass	A	17 ft	-	38
63	Charlotte Lake	Wright	A	17.1 ft	-	38
64	Big Mcdonald Lake	Otter Tail	A	16.4 ft	-	38
65	Bass Lake	Otter Tail	A	16.9 ft	-	40
66	Bass Lake	Crow Wing	A	16.1 ft	-	37
67	Bass Lake	Itasca	A	18.2 ft	-	35
68	Bass Lake	Cass	A	-	-	36
69	Island Lake	Cass	A	15 ft	-	39
70	Island Lake	Crow Wing	A	15.3 ft	-	39
71	Island Lake	Cass	A	17.5 ft	-	35
72	Island Lake	Beltrami	A	16 ft	-	37
73	Island Lake	Hubbard	A	16.4 ft	-	37
74	Crooked Lake	Hubbard	A	19.2 ft	-	34
75	Crooked Lake	Crow Wing	A	15 ft	-	38
76	Portage Lake	Cass	A	22.8 ft	-	32
77	Cedar Lake	Morrison	A	16.4 ft	-	38
78	Big Pine Lake	Aitkin	A	16.5 ft	-	40
79	Lizzie Lake	Otter Tail	A	16.4 ft	-	39
80	Eagles Nest Lake	St. Louis	A	15.5 ft	-	38
81	Turtle Lake	Becker	A	23 ft	-	33
82	Turtle Lake	Itasca	A	17.1 ft	-	35
83	Lower Bottle Lake	Hubbard	A	15 ft	-	38
84	Pokegama Lake	Itasca	A	16 ft	-	39
85	Sandy Lake	Beltrami	A	16 ft	-	36
86	Pickerel Lake	Becker	A	18 ft	-	37
87	Pickerel Lake	Clearwater	A	16.1 ft	-	36
88	Strawberry Lake	Becker	A	17.8 ft	-	34
89	Middle Cormorant Lake	Becker	A	15.1 ft	-	40
90	Mcavity Lake	Itasca	A	17 ft	-	36
91	Gull Lake	Cook	A	16.4 ft	-	36
92	Upper Bottle Lake	Hubbard	A	16 ft	-	38
93	Devil'S Lake	Otter Tail	A	15 ft	-	40
94	Hand Lake	Cass	A	17 ft	-	36
95	Ox Yoke Lake	Cass	A	17.5 ft	-	36
96	Ottertrack Lake	Unknown	A	20.7 ft	-	33
97	Courthouse Lake	Carver	A	20 ft	-	38
98	Miltona Lake	Douglas	A	18.8 ft	-	40
99	Silver Lake	St. Louis	A	19.3 ft	-	38
100	Silver Lake	Crow Wing	A	17 ft	-	36

All oligotrophic lakes (MN+WI) →Wisconsin version →All Minnesota lakes →

Source: EPA National Aquatic Resource Surveys, 2026.