Oligotrophic

Oligotrophic Lakes Across 12 States

Low nutrients, clear water, excellent for swimming. 980 lakes (18% of all graded lakes).

An oligotrophic lake is what most people picture when they think of pristine northern lake country: clarity to depth, no algal scum, cold water that holds dissolved oxygen all the way to the bottom even in August. Across the 12 states LakeQuality covers, 980 lakes register as oligotrophic — 35% 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.

Oligotrophic Mesotrophic Eutrophic Hypereutrophic

Lake	County	State	Grade	Clarity	Depth
East Fox Lake	Crow Wing	MN	A	16.4 ft	65 ft
Bad Medicine Lake	Becker	MN	A	25 ft	84 ft
Big Sugar Bush Lake	Becker	MN	A	16.5 ft	42 ft
Round Lake	Cook	MN	A	16.5 ft	45 ft
Round Lake	Beltrami	MN	A	18 ft	38 ft
Horseshoe Lake	Cass	MN	A	21 ft	51 ft
Long Lake	Cass	MN	A	21.5 ft	115 ft
Long Lake	Clearwater	MN	A	20.5 ft	80 ft
Long Lake	Beltrami	MN	A	20 ft	87 ft
Long Lake	Becker	MN	A	19.3 ft	61 ft
Long Lake	Cass	MN	A	17 ft	37 ft
Long Lake	Itasca	MN	A	16.7 ft	72 ft
Long Lake	Itasca	MN	A	16.9 ft	85 ft
Dead Lake	Hubbard	MN	A	16 ft	34 ft
West Twin Lake	Crow Wing	MN	A	20 ft	-
Sunshine Lake	St. Louis	MN	A	20 ft	37 ft
Otter Lake	Otter Tail	MN	A	18 ft	64 ft
Ossawinnamakee Lake	Crow Wing	MN	A	20 ft	63 ft
Clear Lake	Crow Wing	MN	A	18 ft	63 ft
Clear Lake	Itasca	MN	A	14.9 ft	30 ft
Eagle Lake	Otter Tail	MN	A	22.6 ft	46 ft
West Fox Lake	Crow Wing	MN	A	15 ft	55 ft
Spearhead Lake	Hubbard	MN	A	15 ft	81 ft
Ida Lake	Douglas	MN	A	16.4 ft	106 ft
Star Lake	Crow Wing	MN	A	19 ft	83 ft
Star Lake	Otter Tail	MN	A	17 ft	94 ft
Fish Lake	Otter Tail	MN	A	18 ft	69 ft
Jenny Lake	Lake	MN	A	15.5 ft	93 ft
Hamlet Lake	Crow Wing	MN	A	18.5 ft	88 ft
Birch Lake	Cook	MN	A	18 ft	69 ft
Birch Lake	Unknown	MN	A	15 ft	34 ft
Woman Lake	Cass	MN	A	15 ft	-
Girl Lake	Cass	MN	A	17.6 ft	81 ft
Charlotte Lake	Wright	MN	A	17.1 ft	46 ft
Bass Lake	Otter Tail	MN	A	17.4 ft	-
Bass Lake	Crow Wing	MN	A	16.1 ft	47 ft
Bass Lake	Itasca	MN	A	18.2 ft	65 ft
Bass Lake	Cass	MN	A	-	55 ft
Crooked Lake	Stearns	MN	A	15.5 ft	35 ft
Crooked Lake	Hubbard	MN	A	19 ft	-
Crooked Lake	Crow Wing	MN	A	15 ft	54 ft
Cedar Lake	Morrison	MN	A	16.2 ft	88 ft
Square Lake	Washington	MN	A	17 ft	68 ft
Lower Bottle Lake	Hubbard	MN	A	15 ft	110 ft
Big Pine Lake	Aitkin	MN	A	17 ft	78 ft
Strawberry Lake	Becker	MN	A	17.5 ft	40 ft
Mcavity Lake	Itasca	MN	A	17.3 ft	29 ft
Gull Lake	Cook	MN	A	15.5 ft	-
Deep Portage Lake	Cass	MN	A	15.4 ft	105 ft
Little Wabana Lake	Itasca	MN	A	24 ft	57 ft
Clearwater Lake	Cook	MN	A	29 ft	65 ft
Clearwater Lake	Lake	MN	A	18 ft	46 ft
Lower Hay Lake	Crow Wing	MN	A	18.5 ft	100 ft
Latoka Lake	Douglas	MN	A	19 ft	108 ft
Fullers Lake: East Basin	Beltrami	MN	A	15 ft	-
Pike Lake	Cook	MN	A	17.4 ft	45 ft
Pike Lake	St. Louis	MN	A	18 ft	60 ft
Unnamed Lake	Otter Tail	MN	A	15.1 ft	95 ft
Maple Lake	Itasca	MN	A	15.3 ft	39 ft
Shallow Lake	Itasca	MN	A	16.4 ft	85 ft
Trout Lake	Itasca	MN	A	16 ft	135 ft
Trout Lake	Itasca	MN	A	18 ft	157 ft
Trout Lake	Cook	MN	A	18.4 ft	77 ft
Eddy Lake	Lake	MN	A	17 ft	95 ft
Cowdry Lake	Douglas	MN	A	17.1 ft	52 ft
Bear Lake	Lake	MN	A	17.4 ft	31 ft
Blue Lake	Hubbard	MN	A	17.3 ft	84 ft
Blue Lake	Crow Wing	MN	A	20 ft	48 ft
Partridge Lake	Crow Wing	MN	A	16.2 ft	42 ft
Sand Lake	Cass	MN	A	20 ft	54 ft
Tofte Lake	Lake	MN	A	18.5 ft	73 ft
Green Lake	Beltrami	MN	A	18.5 ft	-
Big Mcdonald Lake	Otter Tail	MN	A	17.4 ft	46 ft
Island Lake	Cass	MN	A	15.5 ft	45 ft
Island Lake	Crow Wing	MN	A	15.1 ft	76 ft
Island Lake	Cass	MN	A	17.5 ft	40 ft
Island Lake	Beltrami	MN	A	16 ft	-
Island Lake	Hubbard	MN	A	16.4 ft	32 ft
Moose Lake	Beltrami	MN	A	15.1 ft	71 ft
Portage Lake	Cass	MN	A	21 ft	84 ft
Lizzie Lake	Otter Tail	MN	A	16.4 ft	66 ft
Eagles Nest Lake	St. Louis	MN	A	15.5 ft	49 ft
Turtle Lake	Becker	MN	A	23 ft	73 ft
Turtle Lake	Itasca	MN	A	17.1 ft	54 ft
Rice Lake	Itasca	MN	A	15 ft	68 ft
Pokegama Lake	Itasca	MN	A	16.1 ft	112 ft
Sandy Lake	Beltrami	MN	A	16 ft	-
Pickerel Lake	Becker	MN	A	18 ft	74 ft
Pickerel Lake	Clearwater	MN	A	16.1 ft	60 ft
Middle Cormorant Lake	Becker	MN	A	15.1 ft	40 ft
Upper Bottle Lake	Hubbard	MN	A	16 ft	55 ft
Ox Yoke Lake	Cass	MN	A	17.5 ft	42 ft
Ottertrack Lake	Lake	MN	A	20 ft	70 ft
West Battle Lake	Otter Tail	MN	A	18 ft	108 ft
Wabana Lake	Itasca	MN	A	18 ft	115 ft
Little Mantrap Lake	Hubbard	MN	A	17 ft	54 ft
Caribou Lake	Itasca	MN	A	31 ft	152 ft
Kimball Lake	Crow Wing	MN	A	18.4 ft	77 ft
West Sylvia Lake	Wright	MN	A	22 ft	97 ft
Serpent Lake	Crow Wing	MN	A	25 ft	65 ft

Showing 100 of 980 oligotrophic lakes.

Frequently Asked Questions

What is an oligotrophic lake?

Low nutrients, clear water, excellent for swimming. There are 980 oligotrophic lakes across the 12 states LakeQuality covers, representing 18% of all graded lakes.

Can you swim in oligotrophic lakes?

Oligotrophic lakes are excellent for swimming, they have crystal clear water with minimal algae and very low nutrient levels.

Featured Oligotrophic Lakes

East Fox Lake

Crow Wing County, MN · Grade A

Bad Medicine Lake

Becker County, MN · Grade A

Big Sugar Bush Lake

Becker County, MN · Grade A

Round Lake

Cook County, MN · Grade A

Round Lake

Beltrami County, MN · Grade A

Horseshoe Lake

Cass County, MN · Grade A

Source: EPA National Aquatic Resource Surveys, 2026.