Oligotrophic Lakes in Minnesota

446 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, 446 lakes register as oligotrophic — 56% 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	16.4 ft	65 ft	37
2	Bad Medicine Lake	Becker	A	25 ft	84 ft	30
3	Big Sugar Bush Lake	Becker	A	16.5 ft	42 ft	37
4	Round Lake	Cook	A	16.5 ft	45 ft	36
5	Round Lake	Beltrami	A	18 ft	38 ft	34
6	Horseshoe Lake	Cass	A	21 ft	51 ft	33
7	Long Lake	Cass	A	21.5 ft	115 ft	34
8	Long Lake	Clearwater	A	20.5 ft	80 ft	33
9	Long Lake	Beltrami	A	20 ft	87 ft	33
10	Long Lake	Becker	A	19.3 ft	61 ft	34
11	Long Lake	Cass	A	17 ft	37 ft	36
12	Long Lake	Itasca	A	16.7 ft	72 ft	35
13	Long Lake	Itasca	A	16.9 ft	85 ft	37
14	Dead Lake	Hubbard	A	16 ft	34 ft	37
15	West Twin Lake	Crow Wing	A	20 ft	-	34
16	Sunshine Lake	St. Louis	A	20 ft	37 ft	34
17	Otter Lake	Otter Tail	A	18 ft	64 ft	35
18	Ossawinnamakee Lake	Crow Wing	A	20 ft	63 ft	35
19	Clear Lake	Crow Wing	A	18 ft	63 ft	35
20	Clear Lake	Itasca	A	14.9 ft	30 ft	37
21	Eagle Lake	Otter Tail	A	22.6 ft	46 ft	30
22	West Fox Lake	Crow Wing	A	15 ft	55 ft	39
23	Spearhead Lake	Hubbard	A	15 ft	81 ft	38
24	Ida Lake	Douglas	A	16.4 ft	106 ft	40
25	Star Lake	Crow Wing	A	19 ft	83 ft	37
26	Star Lake	Otter Tail	A	17 ft	94 ft	39
27	Fish Lake	Otter Tail	A	18 ft	69 ft	38
28	Jenny Lake	Lake	A	15.5 ft	93 ft	38
29	Hamlet Lake	Crow Wing	A	18.5 ft	88 ft	35
30	Birch Lake	Cook	A	18 ft	69 ft	35
31	Birch Lake	Unknown	A	15 ft	34 ft	38
32	Woman Lake	Cass	A	15 ft	-	38
33	Girl Lake	Cass	A	17.6 ft	81 ft	38
34	Charlotte Lake	Wright	A	17.1 ft	46 ft	39
35	Bass Lake	Otter Tail	A	17.4 ft	-	39
36	Bass Lake	Crow Wing	A	16.1 ft	47 ft	37
37	Bass Lake	Itasca	A	18.2 ft	65 ft	35
38	Bass Lake	Cass	A	-	55 ft	36
39	Crooked Lake	Stearns	A	15.5 ft	35 ft	40
40	Crooked Lake	Hubbard	A	19 ft	-	34
41	Crooked Lake	Crow Wing	A	15 ft	54 ft	38
42	Cedar Lake	Morrison	A	16.2 ft	88 ft	38
43	Square Lake	Washington	A	17 ft	68 ft	37
44	Lower Bottle Lake	Hubbard	A	15 ft	110 ft	38
45	Big Pine Lake	Aitkin	A	17 ft	78 ft	40
46	Strawberry Lake	Becker	A	17.5 ft	40 ft	35
47	Mcavity Lake	Itasca	A	17.3 ft	29 ft	36
48	Gull Lake	Cook	A	15.5 ft	-	36
49	Deep Portage Lake	Cass	A	15.4 ft	105 ft	37
50	Little Wabana Lake	Itasca	A	24 ft	57 ft	31
51	Clearwater Lake	Cook	A	29 ft	65 ft	26
52	Clearwater Lake	Lake	A	18 ft	46 ft	35
53	Lower Hay Lake	Crow Wing	A	18.5 ft	100 ft	38
54	Latoka Lake	Douglas	A	19 ft	108 ft	37
55	Fullers Lake: East Basin	Beltrami	A	15 ft	-	37
56	Pike Lake	Cook	A	17.4 ft	45 ft	34
57	Pike Lake	St. Louis	A	18 ft	60 ft	35
58	Unnamed Lake	Otter Tail	A	15.1 ft	95 ft	37
59	Maple Lake	Itasca	A	15.3 ft	39 ft	38
60	Shallow Lake	Itasca	A	16.4 ft	85 ft	36
61	Trout Lake	Itasca	A	16 ft	135 ft	37
62	Trout Lake	Itasca	A	18 ft	157 ft	29
63	Trout Lake	Cook	A	18.4 ft	77 ft	36
64	Eddy Lake	Lake	A	17 ft	95 ft	36
65	Cowdry Lake	Douglas	A	17.1 ft	52 ft	40
66	Bear Lake	Lake	A	17.4 ft	31 ft	36
67	Blue Lake	Hubbard	A	17.3 ft	84 ft	35
68	Blue Lake	Crow Wing	A	20 ft	48 ft	34
69	Partridge Lake	Crow Wing	A	16.2 ft	42 ft	37
70	Sand Lake	Cass	A	20 ft	54 ft	34
71	Tofte Lake	Lake	A	18.5 ft	73 ft	35
72	Green Lake	Beltrami	A	18.5 ft	-	34
73	Big Mcdonald Lake	Otter Tail	A	17.4 ft	46 ft	38
74	Island Lake	Cass	A	15.5 ft	45 ft	39
75	Island Lake	Crow Wing	A	15.1 ft	76 ft	39
76	Island Lake	Cass	A	17.5 ft	40 ft	36
77	Island Lake	Beltrami	A	16 ft	-	37
78	Island Lake	Hubbard	A	16.4 ft	32 ft	37
79	Moose Lake	Beltrami	A	15.1 ft	71 ft	38
80	Portage Lake	Cass	A	21 ft	84 ft	33
81	Lizzie Lake	Otter Tail	A	16.4 ft	66 ft	39
82	Eagles Nest Lake	St. Louis	A	15.5 ft	49 ft	35
83	Turtle Lake	Becker	A	23 ft	73 ft	33
84	Turtle Lake	Itasca	A	17.1 ft	54 ft	35
85	Rice Lake	Itasca	A	15 ft	68 ft	38
86	Pokegama Lake	Itasca	A	16.1 ft	112 ft	39
87	Sandy Lake	Beltrami	A	16 ft	-	36
88	Pickerel Lake	Becker	A	18 ft	74 ft	37
89	Pickerel Lake	Clearwater	A	16.1 ft	60 ft	36
90	Middle Cormorant Lake	Becker	A	15.1 ft	40 ft	40
91	Upper Bottle Lake	Hubbard	A	16 ft	55 ft	38
92	Ox Yoke Lake	Cass	A	17.5 ft	42 ft	36
93	Ottertrack Lake	Lake	A	20 ft	70 ft	34
94	West Battle Lake	Otter Tail	A	18 ft	108 ft	35
95	Wabana Lake	Itasca	A	18 ft	115 ft	35
96	Little Mantrap Lake	Hubbard	A	17 ft	54 ft	35
97	Caribou Lake	Itasca	A	31 ft	152 ft	28
98	Kimball Lake	Crow Wing	A	18.4 ft	77 ft	36
99	West Sylvia Lake	Wright	A	22 ft	97 ft	33
100	Serpent Lake	Crow Wing	A	25 ft	65 ft	35

All oligotrophic lakes →Wisconsin version →Illinois version →Michigan version →Iowa version →Ohio version →Pennsylvania version →New York version →Missouri version →Indiana version →North Dakota 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 →All Minnesota lakes →

Source: EPA National Aquatic Resource Surveys, 2026.