Minnesota Lake Water Quality

Water quality grades for 2,248 monitored lakes across 74 counties.

Minnesota's 2,248 graded lakes draw on monitoring done by the Minnesota Pollution Control Agency and the Minnesota DNR, plus volunteer Citizen Lake Monitoring Network samplers who do the actual Secchi-disk work most years. Around 29% of the state's lakes pull an A — 657 top-tier waters. The B and C brackets together hold most of the rest, with the F bracket capturing 281 stressed lakes mostly in the agricultural south of the state.

Most Minnesota lakes sit in the mesotrophic band — moderate productivity, decent clarity, capable of supporting both warm-water and cool-water fisheries. This is the band where well-managed working lakes tend to land. The cleanest county on average is Hubbard (grade B); the most-stressed is Benton. The gap between the top and bottom counties is large enough that "Minnesota lake water quality" hides real local variation.

Rank	Lake	County	Grade	Clarity	Max Depth
1	East Fox Lake	Crow Wing	A	16.1 ft	65 ft
2	Deep Portage Lake	Cass	A	15.4 ft	105 ft
3	Little Wabana Lake	Itasca	A	23.8 ft	57 ft
4	Clearwater Lake	Cook	A	30 ft	65 ft
5	Clearwater Lake	Lake	A	18 ft	46 ft
6	Lower Hay Lake	Crow Wing	A	19 ft	100 ft
7	Latoka Lake	Douglas	A	19 ft	108 ft
8	Bad Medicine Lake	Becker	A	25 ft	84 ft
9	Big Sugar Bush Lake	Becker	A	17 ft	42 ft
10	Pelican Lake	Otter Tail	A	16.1 ft	55 ft
11	Fullers Lake: East Basin	Beltrami	A	49.2 ft	-
12	Birch Lake	Wright	A	15 ft	52 ft
13	Birch Lake	Cook	A	18 ft	69 ft
14	Birch Lake	Unknown	A	15 ft	34 ft
15	Round Lake	Aitkin	A	15.3 ft	59 ft
16	Round Lake	Cook	A	16.5 ft	45 ft
17	Round Lake	Beltrami	A	59.1 ft	-
18	Pike Lake	Cook	A	17.8 ft	45 ft
19	Pike Lake	St. Louis	A	18 ft	60 ft
20	Whitefish Lake	Crow Wing	A	15.1 ft	138 ft
21	Horseshoe Lake	Cass	A	21 ft	51 ft
22	Long Lake	Clearwater	A	20 ft	80 ft
23	Long Lake	Cass	A	21.8 ft	115 ft
24	Long Lake	Beltrami	A	20 ft	87 ft
25	Long Lake	Becker	A	20 ft	61 ft

Rank	Lake	County	Grade	Clarity
1	Lower Sioux Hank Lake	Redwood	F	-
2	Dune Lake	Beltrami	F	-
3	Fourth Lake	Chisago	F	-
4	Gonz Lake	Wright	F	-
5	Snyder Lake	Hennepin	F	-
6	East Arctic Lake	Scott	F	-
7	Tadd Lake	Kandiyohi	F	1.6 ft
8	Manomin Lake	Lake	F	2 ft
9	South Stanchfield Lake	Isanti	F	2.5 ft
10	Kauppi Lake	St. Louis	F	3 ft
11	Kansas Lake	Watonwan	F	1.6 ft
12	North Stanchfield Lake	Isanti	F	2.8 ft
13	Upper Tad Lake	Kandiyohi	F	1 ft
14	Gleason Lake	Hennepin	F	1.7 ft
15	Mountain Lake	Cottonwood	F	1.2 ft
16	Bella Lake	Nobles	F	1 ft
17	Beaulieu Lake	Mahnomen	F	1.3 ft
18	Olson Lake	Big Stone	F	0.7 ft
19	Little Kettle Lake	Carlton	F	3.3 ft
20	Grossman Slough Lake	Stevens	F	2.3 ft
21	Grey Cloud Slough Lake	Washington	F	3.3 ft
22	Mcmahon Lake	Scott	F	3 ft
23	Greenleaf Lake	Meeker	F	2.8 ft
24	Fisher Lake	Scott	F	0.7 ft
25	Marshan Lake	Anoka	F	1.2 ft

Minnesota Lake Water Quality

Lake Map

Counties

Top 25 Cleanest Lakes

25 Lakes Needing Attention