Most Polluted Lakes in Minnesota & Wisconsin

The 50 lakes with the lowest water quality grades. These lakes have high phosphorus, excessive algae, or very low visibility. Swimming is generally not recommended.

Rank	Lake	County	State	Grade	Clarity	Phosphorus	Algae
1	Kabetogama Lake	St. Louis	MN	F	2.6 ft	—	—
2	North Long Lake	Ramsey	MN	F	2.5 ft	102 µg/L	—
3	Mud Lake	Hennepin	MN	F	0.9 ft	150 µg/L	—
4	Mud Lake	Hennepin	MN	F	3 ft	196 µg/L	—
5	Mud Lake	Otter Tail	MN	F	1.6 ft	—	—
6	Mud Lake	Stearns	MN	F	3 ft	166 µg/L	—
7	Snelling Lake	Hennepin	MN	F	1.6 ft	—	—
8	Pike Lake	Scott	MN	F	2 ft	181.5 µg/L	—
9	Pike Lake	Ramsey	MN	F	2.3 ft	125 µg/L	—
10	Horseshoe Lake	Rice	MN	F	2 ft	—	—
11	Long Lake	Cottonwood	MN	F	1 ft	—	—
12	Unnamed Lake	Ramsey	MN	F	1 ft	172.5 µg/L	—
13	Unnamed Lake	Meeker	MN	F	0.7 ft	224 µg/L	—
14	Unnamed Lake	Benton	MN	F	1.5 ft	—	—
15	Unnamed Lake	Becker	MN	F	1.2 ft	—	—
16	Unnamed Lake	Pope	MN	F	3 ft	—	—
17	Unnamed Lake	Douglas	MN	F	3.3 ft	—	—
18	Unnamed Lake	Otter Tail	MN	F	1.3 ft	—	—
19	Unnamed Lake	Becker	MN	F	2.4 ft	—	—
20	Unnamed Lake	Big Stone	MN	F	2 ft	518.5 µg/L	—
21	Unnamed Lake	Stevens	MN	F	1.1 ft	—	—
22	Unnamed Lake	Swift	MN	F	0.7 ft	224 µg/L	—
23	Unnamed Lake	Wright	MN	F	1.6 ft	—	—
24	Unnamed Lake	Watonwan	MN	F	1 ft	275 µg/L	—
25	Unnamed Lake	Itasca	MN	F	3.3 ft	—	—
26	Unnamed Lake	Grant	MN	F	0.7 ft	269 µg/L	—
27	Unnamed Lake	Hennepin	MN	F	—	220.5 µg/L	—
28	Jonathan Lake	Carver	MN	F	1.5 ft	157.5 µg/L	—
29	Peltier Lake	Anoka	MN	F	2 ft	361.5 µg/L	—
30	Tetonka Lake	Le Sueur	MN	F	3 ft	363 µg/L	—
31	Wakanda Lake	Kandiyohi	MN	F	0.5 ft	—	—
32	Saint Johns Lake	Kandiyohi	MN	F	0.5 ft	188 µg/L	—
33	Clear Lake	Meeker	MN	F	2.5 ft	140 µg/L	—
34	Clear Lake	Brown	MN	F	0.8 ft	196 µg/L	55.6 µg/L
35	Clear Lake	Waseca	MN	F	2.5 ft	151 µg/L	—
36	Clear Lake	Stevens	MN	F	0.7 ft	288 µg/L	—
37	Eagle Lake	Carver	MN	F	2.3 ft	165.5 µg/L	—
38	Eagle Lake	Blue Earth	MN	F	1 ft	—	—
39	Ballantyne Lake	Blue Earth	MN	F	2.5 ft	91 µg/L	—
40	Fish Lake	Kanabec	MN	F	2 ft	—	—
41	Fish Lake	Becker	MN	F	1 ft	136 µg/L	—
42	Sand Lake	Stearns	MN	F	2.5 ft	—	—
43	Hook Lake	McLeod	MN	F	3 ft	—	—
44	Wheeler North Lake	Kandiyohi	MN	F	1 ft	303 µg/L	—
45	Venus Lake	Douglas	MN	F	2.6 ft	—	—
46	Allie Lake	Renville	MN	F	2 ft	232 µg/L	98.3 µg/L
47	Shell Lake	St. Louis	MN	F	3 ft	—	—
48	Roberds Lake	Rice	MN	F	2 ft	300 µg/L	—
49	Charlotte Lake	Stevens	MN	F	0.9 ft	237 µg/L	—
50	Island Lake	Lyon	MN	F	2 ft	123 µg/L	—