What are oligotrophic lakes in Minnesota?

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

What does oligotrophic mean?

Low nutrients, clear water, excellent for swimming.

Oligotrophic Lakes in Minnesota

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, 232 lakes register as oligotrophic — 59% 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.

Oligotrophic lakes almost always carry the lowest phosphorus and chlorophyll-a readings on record, since the same low-nutrient conditions produce both the trophic class and the clear water.

#	Lake	County	Clarity	Depth	TSI
1	Rainy Lake	Cass	13.9 ft	29 ft	38
2	East Fox Lake	Crow Wing	16.4 ft	65 ft	38
3	Deep Portage Lake	Cass	15.4 ft	105 ft	36
4	Clearwater Lake	Cook	29 ft	65 ft	29
5	Lower Hay Lake	Crow Wing	18.5 ft	100 ft	39
6	Latoka Lake	Douglas	19 ft	108 ft	37
7	Bad Medicine Lake	Becker	25 ft	84 ft	32
8	Big Sugar Bush Lake	Becker	16.5 ft	42 ft	38
9	Pelican Lake	Crow Wing	14.3 ft	104 ft	39
10	Fullers Lake	Beltrami	15 ft	-	38
11	Birch Lake	Cook	18 ft	69 ft	35
12	Round Lake	Aitkin	14.5 ft	125 ft	39
13	Round Lake	Cook	16.5 ft	45 ft	36
14	Round Lake	Beltrami	18 ft	38 ft	35
15	Ada Lake	Cass	14 ft	60 ft	39
16	Pike Lake	Cook	17.4 ft	45 ft	36
17	Long Lake	Clearwater	20.5 ft	80 ft	33
18	Long Lake	Cass	21.5 ft	115 ft	37
19	Long Lake	Beltrami	20 ft	87 ft	34
20	Long Lake	Becker	19.5 ft	61 ft	36
21	Long Lake	Beltrami	14 ft	-	37
22	Long Lake	Itasca	16.7 ft	72 ft	38
23	Long Lake	Itasca	16.9 ft	85 ft	37
24	Dead Lake	Hubbard	16 ft	34 ft	39
25	Maple Lake	Cass	13.3 ft	45 ft	39
26	Maple Lake	Itasca	15.3 ft	39 ft	40
27	West Twin Lake	Crow Wing	13.3 ft	42 ft	39
28	Shallow Lake	Itasca	16.4 ft	85 ft	38
29	Trout Lake	Itasca	18 ft	157 ft	30
30	Trout Lake	Cook	18.4 ft	77 ft	35
31	Deer Lake	Itasca	13.1 ft	121 ft	39
32	Cowdry Lake	Douglas	17.1 ft	52 ft	40
33	Ossawinnamakee Lake	Crow Wing	20 ft	63 ft	35
34	Clear Lake	Crow Wing	18 ft	63 ft	36
35	Clear Lake	Itasca	14.9 ft	30 ft	40
36	Spectacle Lake	Isanti	13.8 ft	51.5 ft	39
37	Bear Lake	Lake	17.4 ft	31 ft	38
38	Blue Lake	Hubbard	17.3 ft	84 ft	36
39	Eagle Lake	Otter Tail	22.6 ft	46 ft	32
40	West Fox Lake	Crow Wing	15 ft	55 ft	39
41	Star Lake	Crow Wing	19 ft	83 ft	37
42	Fish Lake	Otter Tail	18 ft	69 ft	38
43	Benedict Lake	Hubbard	11.5 ft	91 ft	39
44	Square Lake	Washington	17 ft	68 ft	38
45	Shell Lake	Beltrami	13 ft	-	39
46	Woman Lake	Cass	15 ft	-	40
47	Green Lake	Beltrami	18.5 ft	-	34
48	Girl Lake	Cass	17.6 ft	81 ft	39
49	Mow Lake	Hubbard	14.5 ft	34 ft	39
50	Charlotte Lake	Wright	17.1 ft	46 ft	39
51	Big Mcdonald Lake	Otter Tail	17.4 ft	46 ft	39
52	Bass Lake	Otter Tail	17.4 ft	-	39
53	Bass Lake	Crow Wing	16.1 ft	47 ft	38
54	Bass Lake	Itasca	18.2 ft	65 ft	36
55	Island Lake	St. Louis	14.5 ft	65 ft	38
56	Island Lake	Crow Wing	15.1 ft	76 ft	39
57	Island Lake	Cass	17.5 ft	40 ft	37
58	Island Lake	Beltrami	16 ft	-	38
59	Island Lake	Hubbard	16.4 ft	32 ft	39
60	Moose Lake	Beltrami	15.1 ft	71 ft	38
61	Crooked Lake	Hubbard	19 ft	-	36
62	Crooked Lake	Crow Wing	15 ft	54 ft	39
63	Cedar Lake	Morrison	16.2 ft	88 ft	37
64	Big Pine Lake	Aitkin	17 ft	78 ft	38
65	Lizzie Lake	Otter Tail	16.4 ft	66 ft	39
66	Turtle Lake	Becker	23 ft	73 ft	34
67	Turtle Lake	Itasca	17.1 ft	54 ft	36
68	Lower Bottle Lake	Hubbard	15 ft	110 ft	38
69	Pokegama Lake	Itasca	16.1 ft	112 ft	39
70	Sandy Lake	Beltrami	16 ft	-	37
71	Pickerel Lake	Becker	18 ft	74 ft	37
72	Strawberry Lake	Becker	17.5 ft	40 ft	34
73	Gull Lake	Cook	15.5 ft	-	37
74	Henderson Lake	Kandiyohi	13.5 ft	57 ft	38
75	Upper Birch Lake	Isanti	10.8 ft	-	39
76	Upper Bottle Lake	Hubbard	16 ft	55 ft	39
77	Courthouse Lake	Carver	18.9 ft	57 ft	39
78	Silver Lake	St. Louis	19.3 ft	29 ft	39
79	Heart Lake	Beltrami	14.5 ft	-	39
80	West Battle Lake	Otter Tail	18 ft	108 ft	37
81	Wabana Lake	Itasca	18 ft	115 ft	36
82	Roy Lake	Crow Wing	11.7 ft	26 ft	40
83	Little Mantrap Lake	Hubbard	17 ft	54 ft	37
84	Clitherall Lake	Otter Tail	14.1 ft	69 ft	40
85	Kimball Lake	Crow Wing	18.4 ft	77 ft	36
86	Baby Lake	Cass	12.5 ft	69 ft	40
87	Crystal Lake	Cass	16 ft	40 ft	36
88	West Sylvia Lake	Wright	22 ft	97 ft	34
89	Serpent Lake	Crow Wing	25 ft	65 ft	35
90	North Twin Lake	Beltrami	17.4 ft	59 ft	36
91	Stuart Lake	Otter Tail	17.5 ft	49 ft	40
92	North Star Lake	Itasca	19 ft	90 ft	36
93	Pleasant Lake	Cass	15.5 ft	72 ft	39
94	Little Bass Lake	Beltrami	16 ft	22 ft	38
95	Pulaski Lake	Wright	18 ft	-	38
96	Little Mcdonald Lake	Otter Tail	26.5 ft	109 ft	33
97	Bay Lake	Crow Wing	18.5 ft	74 ft	36
98	Webb Lake	Cass	18 ft	84 ft	38
99	Little Hubert Lake	Crow Wing	18 ft	41 ft	39
100	Big Trout Lake	Crow Wing	16.9 ft	128 ft	37

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 →Ontario version →Québec version →Nova Scotia version →British Columbia version →Newfoundland and Labrador version →All Minnesota lakes →

Source: EPA National Aquatic Resource Surveys, 2026.