Grade F Lakes, Very Poor

719 lakes (13% of all graded lakes)

Grade F is the bottom of the rubric: clarity often under 3 feet, very high phosphorus, dense algal communities, frequent harmful-algal-bloom risk. 719 lakes (13% of the dataset) end up here.

A large share of the bracket reads as hypereutrophic — heavy nutrient loading, persistent blooms, low summer transparency. These conditions are usually structural rather than transient. Almost none of the F-grade bracket is deep — 3% of lakes here break 50 feet. The combination of shallow basin plus high nutrient input is what produces an F.

A B C D F

719

Total Lakes

States Covered

MN 309WI 114IA 99MO 82IL 48MI 22ND 18NY 15IN 6OH 5SD 1

Lake	County	State	Clarity	Depth	Fish
Mud Lake	Washington	MN	1.2 ft	-	0
Emily Lake	Chisago	MN	1.6 ft	-	0
Rice Lake	Scott	MN	1.7 ft	-	0
Victoria Lake	Hennepin	MN	1.2 ft	-	0
Pioneer Lake	Chisago	MN	2 ft	8 ft	4
Budd Lake	Martin	MN	3.2 ft	23 ft	20
Mcmahon Lake	Scott	MN	2.3 ft	14 ft	9
Thole Lake	Scott	MN	2.8 ft	12 ft	12
Dickman Lake	Dakota	MN	1.6 ft	-	0
Willmert Lake	Martin	MN	3.3 ft	8 ft	11
Cottontail Lake	Jackson	MO	1.6 ft	-	0
Lamar City Lk. South Arm Lake	Barton	MO	2.1 ft	-	0
Mallard Lake	St. Louis	MO	1.9 ft	-	0
Lake of the Woods-Kc	Jackson	MO	2 ft	-	0
Lamar City Lk. East Arm Lake	Barton	MO	1.9 ft	-	0
Little Dixie Lk. Lake	Callaway	MO	1.7 ft	-	0
Harrisonville City Lake	Cass	MO	1.9 ft	-	0
Lamar City Lk. Nr. Dam Lake	Barton	MO	2 ft	-	0
Lake St. Louis by Dam	St. Charles	MO	2.3 ft	-	0
Raintree Lake	Cass	MO	2.5 ft	-	0
Table Rock L. @ Hampton Hollow Lake	Stone	MO	2.6 ft	-	0
Lamar City Lk. Up Northern Arm Lake	Barton	MO	1.8 ft	-	0
Blind Pony Lake	Saline	MO	2.3 ft	-	0
Mark Twain Lake	Monroe	MO	2.5 ft	-	0
Coot Lake	Jackson	MO	1.6 ft	-	0
Harrison County Lake	Harrison	MO	1.5 ft	-	0
Pomme de Terre Lake	Hickory	MO	1.2 ft	-	0
Fon-du-Lac Reservoir	Jefferson	MO	1.3 ft	-	0
Marceline Lake	Linn	MO	1.9 ft	-	0
Rocky Fork Lake	Boone	MO	2.3 ft	-	0
Mckay Park Lake	Cole	MO	1 ft	-	0
Edwin A Pape Lake	Lafayette	MO	1.8 ft	-	0
Harrisonville Lake	Cass	MO	1.1 ft	-	0
Elmwood Lake	Sullivan	MO	2.7 ft	-	0
Western Stump Lake	Nelson	ND	4.3 ft	77.1 ft	4
Eastern Stump Lake	Nelson	ND	4.7 ft	-	0
Kabetogama Lake	St. Louis	MN	2.6 ft	80 ft	16
North Long Lake	Ramsey	MN	2.5 ft	-	0
Snelling Lake	Hennepin	MN	1.8 ft	9.5 ft	10
Horseshoe Lake	Rice	MN	2 ft	26 ft	13
Long Lake	Stearns	MN	2.5 ft	35 ft	23
Long Lake	Cottonwood	MN	1 ft	-	0
Long Lake	Hennepin	MN	3.3 ft	33 ft	14
Long Lake	Dakota	MN	1.6 ft	-	0
Jonathan Lake	Carver	MN	1.5 ft	-	3
Peltier Lake	Anoka	MN	2.5 ft	18 ft	16
Clear Lake	Meeker	MN	3 ft	18 ft	13
Clear Lake	Brown	MN	0.8 ft	8 ft	12
Clear Lake	Waseca	MN	2.5 ft	34 ft	12
Clear Lake	Stevens	MN	0.7 ft	-	0
Clear Lake	Le Sueur	MN	1.2 ft	18 ft	11
Eagle Lake	Carver	MN	2 ft	14 ft	8
Eagle Lake	Blue Earth	MN	1 ft	9 ft	0
Fish Lake	Kanabec	MN	2 ft	8 ft	21
Fish Lake	Becker	MN	1 ft	-	0
Hook Lake	McLeod	MN	2.5 ft	18 ft	3
Allie Lake	Renville	MN	3 ft	12 ft	13
Roberds Lake	Rice	MN	2.5 ft	43 ft	18
Grace Lake	Carver	MN	2.6 ft	22 ft	11
Charlotte Lake	Stevens	MN	0.9 ft	20 ft	10
Cedar Lake	Scott	MN	2 ft	13 ft	10
Wing Lake	Hennepin	MN	2.1 ft	-	0
Rhine Lake	Pine	MN	2.5 ft	8 ft	9
Lawrence Lake	Houston	MN	2.3 ft	-	0
Mud Lake	Hennepin	MN	0.9 ft	-	0
Mud Lake	Hennepin	MN	3 ft	-	0
Mud Lake	Otter Tail	MN	1.6 ft	-	0
Mud Lake	Stearns	MN	3 ft	20 ft	16
Mud Lake	Martin	MN	1.6 ft	19 ft	17
Pike Lake	Scott	MN	2.3 ft	9 ft	0
Pike Lake	Ramsey	MN	2.3 ft	16 ft	13
Unnamed Lake	Meeker	MN	0.7 ft	15 ft	10
Unnamed Lake	Benton	MN	1.5 ft	-	0
Unnamed Lake	Becker	MN	1.2 ft	-	0
Unnamed Lake	Swift	MN	0.7 ft	-	0
Unnamed Lake	Watonwan	MN	1 ft	-	0
Unnamed Lake	Douglas	MN	3.3 ft	-	0
Unnamed Lake	Becker	MN	2.4 ft	76 ft	17
Unnamed Lake	Otter Tail	MN	1.3 ft	-	0
Unnamed Lake	Big Stone	MN	2 ft	15 ft	8
Unnamed Lake	Wright	MN	1.6 ft	-	0
Unnamed Lake	Pope	MN	3 ft	-	0
Unnamed Lake	Itasca	MN	3.3 ft	-	0
Unnamed Lake	Stevens	MN	1.1 ft	-	0
Unnamed Lake	Grant	MN	0.7 ft	-	0
Unnamed Lake	Brown	MN	0.3 ft	-	0
Unnamed Lake	Hennepin	MN	-	-	0
Tetonka Lake	Le Sueur	MN	3 ft	35 ft	19
Wakanda Lake	Kandiyohi	MN	0.5 ft	-	0
Saint Johns Lake	Kandiyohi	MN	0.5 ft	-	0
Sand Lake	Stearns	MN	2.5 ft	15 ft	0
Wheeler North Lake	Kandiyohi	MN	1 ft	-	0
Union Lake	Rice	MN	3 ft	10 ft	0
Venus Lake	Douglas	MN	3 ft	-	0
Island Lake	Lyon	MN	2 ft	8 ft	6
Emily Lake	Pope	MN	2 ft	6 ft	26
Rice Lake	Hennepin	MN	2.3 ft	11.5 ft	16
Rice Lake	Anoka	MN	2.6 ft	-	0
Rice Lake	Morrison	MN	2 ft	8 ft	0
Thompson Lake	St. Louis	MN	3 ft	9 ft	8

Showing 100 of 719 Grade F lakes.

Frequently Asked Questions

How many lakes have a grade of F?

There are 719 Grade F (Very Poor) lakes across the 12 states LakeQuality covers, led by Minnesota (309) and Wisconsin (114). This represents 13% of all graded lakes.

What does a Grade F mean?

Grade F means very poor water quality with less than 3 ft visibility, very high phosphorus and algae. Potential for harmful algae toxins. Do not swim. Fish kills may occur.

Featured Grade F Lakes

Mud Lake

Washington County, MN · 1.2 ft clarity

Emily Lake

Chisago County, MN · 1.6 ft clarity

Rice Lake

Scott County, MN · 1.7 ft clarity

Victoria Lake

Hennepin County, MN · 1.2 ft clarity

Pioneer Lake

Chisago County, MN · 2 ft clarity

Budd Lake

Martin County, MN · 3.2 ft clarity

Source: EPA National Aquatic Resource Surveys, 2026.