Lake Water Quality Answers
Direct answers to the questions people most often ask about lakes across our 41 covered states. Each answer pulls from EPA water quality data, EPA National Lakes Assessment ecoregion classes, and DNR fish surveys. Drill into a specific lake, a state, a county, or a general topic.
By State
Minnesota
Wisconsin
Illinois
Michigan
Pennsylvania
New York
Missouri
Indiana
North Dakota
Florida
Colorado
North Carolina
Vermont
Oregon
Arkansas
Oklahoma
Kansas
Nebraska
Nevada
Montana
Tennessee
Alabama
Virginia
Kentucky
Georgia
British Columbia
Cleanest Lakes by County
Top counties by lake count in each state. See all 2589 counties →
Minnesota
- Cleanest lakes in St. Louis County(604 lakes)
- Cleanest lakes in Itasca County(579 lakes)
- Cleanest lakes in Cook County(469 lakes)
- Cleanest lakes in Lake County(447 lakes)
- Cleanest lakes in Cass County(397 lakes)
- Cleanest lakes in Otter Tail County(381 lakes)
- Cleanest lakes in Crow Wing County(320 lakes)
- Cleanest lakes in Becker County(306 lakes)
Wisconsin
- Cleanest lakes in Vilas County(400 lakes)
- Cleanest lakes in Oneida County(305 lakes)
- Cleanest lakes in Burnett County(168 lakes)
- Cleanest lakes in Washburn County(161 lakes)
- Cleanest lakes in Polk County(151 lakes)
- Cleanest lakes in Bayfield County(147 lakes)
- Cleanest lakes in Sawyer County(120 lakes)
- Cleanest lakes in Iron County(109 lakes)
Illinois
- Cleanest lakes in Cook County(68 lakes)
- Cleanest lakes in Lake County(65 lakes)
- Cleanest lakes in Mason County(21 lakes)
- Cleanest lakes in Macoupin County(17 lakes)
- Cleanest lakes in McHenry County(15 lakes)
- Cleanest lakes in Jackson County(14 lakes)
- Cleanest lakes in Fulton County(14 lakes)
- Cleanest lakes in Williamson County(13 lakes)
Michigan
- Cleanest lakes in Oakland County(214 lakes)
- Cleanest lakes in Marquette County(160 lakes)
- Cleanest lakes in Gogebic County(136 lakes)
- Cleanest lakes in Iron County(126 lakes)
- Cleanest lakes in Schoolcraft County(123 lakes)
- Cleanest lakes in Livingston County(100 lakes)
- Cleanest lakes in Alger County(96 lakes)
- Cleanest lakes in Cass County(87 lakes)
Iowa
- Cleanest lakes in Dickinson County(24 lakes)
- Cleanest lakes in Emmet County(12 lakes)
- Cleanest lakes in Jackson County(12 lakes)
- Cleanest lakes in Polk County(11 lakes)
- Cleanest lakes in Louisa County(9 lakes)
- Cleanest lakes in Black Hawk County(8 lakes)
- Cleanest lakes in Des Moines County(8 lakes)
- Cleanest lakes in Kossuth County(8 lakes)
Ohio
- Cleanest lakes in Portage County(23 lakes)
- Cleanest lakes in Summit County(18 lakes)
- Cleanest lakes in Mahoning County(11 lakes)
- Cleanest lakes in Columbiana County(9 lakes)
- Cleanest lakes in Geauga County(9 lakes)
- Cleanest lakes in Allen County(8 lakes)
- Cleanest lakes in Perry County(8 lakes)
- Cleanest lakes in Stark County(8 lakes)
Pennsylvania
- Cleanest lakes in Wayne County(97 lakes)
- Cleanest lakes in Pike County(59 lakes)
- Cleanest lakes in Susquehanna County(48 lakes)
- Cleanest lakes in Lackawanna County(41 lakes)
- Cleanest lakes in Luzerne County(37 lakes)
- Cleanest lakes in Monroe County(34 lakes)
- Cleanest lakes in Schuylkill County(22 lakes)
- Cleanest lakes in Bradford County(22 lakes)
New York
- Cleanest lakes in Hamilton County(198 lakes)
- Cleanest lakes in Franklin County(134 lakes)
- Cleanest lakes in Essex County(129 lakes)
- Cleanest lakes in Sullivan County(112 lakes)
- Cleanest lakes in Herkimer County(110 lakes)
- Cleanest lakes in St. Lawrence County(103 lakes)
- Cleanest lakes in Warren County(67 lakes)
- Cleanest lakes in Orange County(61 lakes)
Missouri
- Cleanest lakes in Jackson County(27 lakes)
- Cleanest lakes in Warren County(15 lakes)
- Cleanest lakes in Boone County(15 lakes)
- Cleanest lakes in St. Charles County(14 lakes)
- Cleanest lakes in Vernon County(14 lakes)
- Cleanest lakes in Cass County(13 lakes)
- Cleanest lakes in Ste. Genevieve County(10 lakes)
- Cleanest lakes in St. Francois County(10 lakes)
Indiana
- Cleanest lakes in Steuben County(47 lakes)
- Cleanest lakes in Noble County(41 lakes)
- Cleanest lakes in Kosciusko County(40 lakes)
- Cleanest lakes in LaGrange County(35 lakes)
- Cleanest lakes in LaPorte County(14 lakes)
- Cleanest lakes in Marshall County(12 lakes)
- Cleanest lakes in Whitley County(11 lakes)
- Cleanest lakes in Sullivan County(10 lakes)
North Dakota
- Cleanest lakes in Rolette County(80 lakes)
- Cleanest lakes in Kidder County(54 lakes)
- Cleanest lakes in Stutsman County(51 lakes)
- Cleanest lakes in Bottineau County(47 lakes)
- Cleanest lakes in McLean County(43 lakes)
- Cleanest lakes in Nelson County(37 lakes)
- Cleanest lakes in Burke County(37 lakes)
- Cleanest lakes in McHenry County(32 lakes)
South Dakota
- Cleanest lakes in Marshall County(52 lakes)
- Cleanest lakes in Day County(29 lakes)
- Cleanest lakes in Codington County(23 lakes)
- Cleanest lakes in Clark County(21 lakes)
- Cleanest lakes in Roberts County(20 lakes)
- Cleanest lakes in Lake County(18 lakes)
- Cleanest lakes in Bennett County(16 lakes)
- Cleanest lakes in Miner County(15 lakes)
Florida
- Cleanest lakes in Orange County(445 lakes)
- Cleanest lakes in Lake County(343 lakes)
- Cleanest lakes in Polk County(225 lakes)
- Cleanest lakes in Hillsborough County(189 lakes)
- Cleanest lakes in Seminole County(167 lakes)
- Cleanest lakes in Putnam County(122 lakes)
- Cleanest lakes in Highlands County(108 lakes)
- Cleanest lakes in Marion County(108 lakes)
Colorado
- Cleanest lakes in Larimer County(91 lakes)
- Cleanest lakes in Weld County(55 lakes)
- Cleanest lakes in Boulder County(36 lakes)
- Cleanest lakes in Mesa County(31 lakes)
- Cleanest lakes in Jefferson County(29 lakes)
- Cleanest lakes in Grand County(25 lakes)
- Cleanest lakes in Delta County(24 lakes)
- Cleanest lakes in Jackson County(22 lakes)
North Carolina
- Cleanest lakes in Wake County(18 lakes)
- Cleanest lakes in Moore County(14 lakes)
- Cleanest lakes in Cumberland County(14 lakes)
- Cleanest lakes in Richmond County(13 lakes)
- Cleanest lakes in Guilford County(13 lakes)
- Cleanest lakes in Bladen County(12 lakes)
- Cleanest lakes in Gaston County(10 lakes)
- Cleanest lakes in Orange County(10 lakes)
Vermont
- Cleanest lakes in Rutland County(42 lakes)
- Cleanest lakes in Orleans County(39 lakes)
- Cleanest lakes in Caledonia County(34 lakes)
- Cleanest lakes in Washington County(29 lakes)
- Cleanest lakes in Windsor County(26 lakes)
- Cleanest lakes in Windham County(25 lakes)
- Cleanest lakes in Essex County(22 lakes)
- Cleanest lakes in Bennington County(21 lakes)
Texas
- Cleanest lakes in Brazoria County(71 lakes)
- Cleanest lakes in Henderson County(36 lakes)
- Cleanest lakes in Smith County(30 lakes)
- Cleanest lakes in Cameron County(28 lakes)
- Cleanest lakes in Liberty County(26 lakes)
- Cleanest lakes in Chambers County(23 lakes)
- Cleanest lakes in Harris County(22 lakes)
- Cleanest lakes in Navarro County(22 lakes)
Oregon
- Cleanest lakes in Lake County(124 lakes)
- Cleanest lakes in Klamath County(90 lakes)
- Cleanest lakes in Harney County(70 lakes)
- Cleanest lakes in Lane County(41 lakes)
- Cleanest lakes in Malheur County(39 lakes)
- Cleanest lakes in Deschutes County(30 lakes)
- Cleanest lakes in Linn County(22 lakes)
- Cleanest lakes in Jefferson County(22 lakes)
Arkansas
- Cleanest lakes in Arkansas County(76 lakes)
- Cleanest lakes in Jefferson County(28 lakes)
- Cleanest lakes in Prairie County(27 lakes)
- Cleanest lakes in Desha County(27 lakes)
- Cleanest lakes in Pulaski County(22 lakes)
- Cleanest lakes in Chicot County(21 lakes)
- Cleanest lakes in Crittenden County(21 lakes)
- Cleanest lakes in Miller County(20 lakes)
Oklahoma
- Cleanest lakes in Osage County(21 lakes)
- Cleanest lakes in McCurtain County(17 lakes)
- Cleanest lakes in Pittsburg County(12 lakes)
- Cleanest lakes in Comanche County(12 lakes)
- Cleanest lakes in Kay County(11 lakes)
- Cleanest lakes in Carter County(9 lakes)
- Cleanest lakes in Rogers County(9 lakes)
- Cleanest lakes in Creek County(9 lakes)
Kansas
- Cleanest lakes in Johnson County(20 lakes)
- Cleanest lakes in Linn County(11 lakes)
- Cleanest lakes in Sedgwick County(8 lakes)
- Cleanest lakes in Bourbon County(6 lakes)
- Cleanest lakes in Osage County(6 lakes)
- Cleanest lakes in Miami County(6 lakes)
- Cleanest lakes in Wyandotte County(6 lakes)
- Cleanest lakes in Greenwood County(5 lakes)
Nebraska
- Cleanest lakes in Cherry County(161 lakes)
- Cleanest lakes in Sheridan County(101 lakes)
- Cleanest lakes in Garden County(80 lakes)
- Cleanest lakes in Grant County(23 lakes)
- Cleanest lakes in Brown County(17 lakes)
- Cleanest lakes in Rock County(16 lakes)
- Cleanest lakes in Holt County(12 lakes)
- Cleanest lakes in Morrill County(8 lakes)
Nevada
- Cleanest lakes in Washoe County(61 lakes)
- Cleanest lakes in Churchill County(42 lakes)
- Cleanest lakes in Elko County(33 lakes)
- Cleanest lakes in Humboldt County(21 lakes)
- Cleanest lakes in Nye County(16 lakes)
- Cleanest lakes in Clark County(10 lakes)
- Cleanest lakes in Lincoln County(7 lakes)
- Cleanest lakes in White Pine County(7 lakes)
Arizona
- Cleanest lakes in Coconino County(69 lakes)
- Cleanest lakes in Apache County(59 lakes)
- Cleanest lakes in Navajo County(22 lakes)
- Cleanest lakes in Maricopa County(16 lakes)
- Cleanest lakes in Yavapai County(13 lakes)
- Cleanest lakes in Mohave County(13 lakes)
- Cleanest lakes in Pima County(9 lakes)
- Cleanest lakes in Graham County(9 lakes)
Idaho
- Cleanest lakes in Owyhee County(34 lakes)
- Cleanest lakes in Valley County(26 lakes)
- Cleanest lakes in Idaho County(26 lakes)
- Cleanest lakes in Kootenai County(22 lakes)
- Cleanest lakes in Fremont County(18 lakes)
- Cleanest lakes in Custer County(17 lakes)
- Cleanest lakes in Bonner County(13 lakes)
- Cleanest lakes in Blaine County(12 lakes)
Montana
- Cleanest lakes in Flathead County(108 lakes)
- Cleanest lakes in Glacier County(70 lakes)
- Cleanest lakes in Lincoln County(50 lakes)
- Cleanest lakes in Missoula County(46 lakes)
- Cleanest lakes in Phillips County(42 lakes)
- Cleanest lakes in Carbon County(38 lakes)
- Cleanest lakes in Lake County(38 lakes)
- Cleanest lakes in Beaverhead County(28 lakes)
New Mexico
- Cleanest lakes in Colfax County(40 lakes)
- Cleanest lakes in McKinley County(35 lakes)
- Cleanest lakes in Chaves County(33 lakes)
- Cleanest lakes in Rio Arriba County(24 lakes)
- Cleanest lakes in Cibola County(18 lakes)
- Cleanest lakes in Eddy County(15 lakes)
- Cleanest lakes in Catron County(15 lakes)
- Cleanest lakes in San Juan County(14 lakes)
Tennessee
- Cleanest lakes in Shelby County(18 lakes)
- Cleanest lakes in Lauderdale County(17 lakes)
- Cleanest lakes in Hardeman County(14 lakes)
- Cleanest lakes in Cumberland County(13 lakes)
- Cleanest lakes in Stewart County(11 lakes)
- Cleanest lakes in Henderson County(9 lakes)
- Cleanest lakes in Obion County(8 lakes)
- Cleanest lakes in Fayette County(7 lakes)
Alabama
- Cleanest lakes in Tuscaloosa County(27 lakes)
- Cleanest lakes in Baldwin County(26 lakes)
- Cleanest lakes in Shelby County(21 lakes)
- Cleanest lakes in Jefferson County(18 lakes)
- Cleanest lakes in Hale County(15 lakes)
- Cleanest lakes in Sumter County(15 lakes)
- Cleanest lakes in Covington County(10 lakes)
- Cleanest lakes in St. Clair County(10 lakes)
Virginia
- Cleanest lakes in Franklin County(15 lakes)
- Cleanest lakes in Caroline County(14 lakes)
- Cleanest lakes in James City County(13 lakes)
- Cleanest lakes in Spotsylvania County(13 lakes)
- Cleanest lakes in Sussex County(12 lakes)
- Cleanest lakes in Chesterfield County(12 lakes)
- Cleanest lakes in Stafford County(11 lakes)
- Cleanest lakes in York County(10 lakes)
Kentucky
- Cleanest lakes in Ballard County(18 lakes)
- Cleanest lakes in Christian County(12 lakes)
- Cleanest lakes in Logan County(9 lakes)
- Cleanest lakes in Hopkins County(7 lakes)
- Cleanest lakes in Hardin County(4 lakes)
- Cleanest lakes in Grant County(4 lakes)
- Cleanest lakes in Lincoln County(3 lakes)
- Cleanest lakes in Ohio County(3 lakes)
Utah
- Cleanest lakes in Duchesne County(45 lakes)
- Cleanest lakes in Box Elder County(31 lakes)
- Cleanest lakes in Summit County(28 lakes)
- Cleanest lakes in Garfield County(16 lakes)
- Cleanest lakes in Uintah County(15 lakes)
- Cleanest lakes in Millard County(14 lakes)
- Cleanest lakes in Juab County(14 lakes)
- Cleanest lakes in Sanpete County(13 lakes)
Washington
- Cleanest lakes in King County(92 lakes)
- Cleanest lakes in Okanogan County(58 lakes)
- Cleanest lakes in Snohomish County(52 lakes)
- Cleanest lakes in Grant County(48 lakes)
- Cleanest lakes in Skagit County(40 lakes)
- Cleanest lakes in Pierce County(39 lakes)
- Cleanest lakes in Spokane County(39 lakes)
- Cleanest lakes in Chelan County(38 lakes)
Wyoming
- Cleanest lakes in Fremont County(134 lakes)
- Cleanest lakes in Sublette County(117 lakes)
- Cleanest lakes in Carbon County(71 lakes)
- Cleanest lakes in Albany County(67 lakes)
- Cleanest lakes in Park County(60 lakes)
- Cleanest lakes in Teton County(57 lakes)
- Cleanest lakes in Natrona County(36 lakes)
- Cleanest lakes in Johnson County(32 lakes)
Georgia
- Cleanest lakes in Lowndes County(24 lakes)
- Cleanest lakes in Carroll County(17 lakes)
- Cleanest lakes in Harris County(15 lakes)
- Cleanest lakes in Fulton County(15 lakes)
- Cleanest lakes in Bulloch County(14 lakes)
- Cleanest lakes in Henry County(13 lakes)
- Cleanest lakes in Coweta County(12 lakes)
- Cleanest lakes in Emanuel County(12 lakes)
Massachusetts
- Cleanest lakes in Worcester County(220 lakes)
- Cleanest lakes in Plymouth County(104 lakes)
- Cleanest lakes in Middlesex County(97 lakes)
- Cleanest lakes in Barnstable County(94 lakes)
- Cleanest lakes in Berkshire County(72 lakes)
- Cleanest lakes in Essex County(57 lakes)
- Cleanest lakes in Hampden County(37 lakes)
- Cleanest lakes in Bristol County(37 lakes)
Ontario
- Cleanest lakes in Kenora District County(321 lakes)
- Cleanest lakes in Thunder Bay District County(288 lakes)
- Cleanest lakes in Nipissing District County(266 lakes)
- Cleanest lakes in Sudbury District County(260 lakes)
- Cleanest lakes in Parry Sound District County(229 lakes)
- Cleanest lakes in Algoma District County(215 lakes)
- Cleanest lakes in Haliburton County(187 lakes)
- Cleanest lakes in Muskoka District County(170 lakes)
Québec
- Cleanest lakes in Les Laurentides County(118 lakes)
- Cleanest lakes in Matawinie County(110 lakes)
- Cleanest lakes in Les Pays-d'en-Haut County(109 lakes)
- Cleanest lakes in Antoine-Labelle County(69 lakes)
- Cleanest lakes in Argenteuil County(48 lakes)
- Cleanest lakes in La Vallée-de-la-Gatineau County(36 lakes)
- Cleanest lakes in Papineau County(33 lakes)
- Cleanest lakes in Maskinongé County(32 lakes)
Nova Scotia
- Cleanest lakes in Halifax County(239 lakes)
- Cleanest lakes in Guysborough County(105 lakes)
- Cleanest lakes in Lunenburg County(99 lakes)
- Cleanest lakes in Yarmouth County(78 lakes)
- Cleanest lakes in Digby County(70 lakes)
- Cleanest lakes in Queens County(60 lakes)
- Cleanest lakes in Annapolis County(55 lakes)
- Cleanest lakes in Kings County(44 lakes)
British Columbia
- Cleanest lakes in Squamish County(9 lakes)
- Cleanest lakes in Okanagan River County(8 lakes)
- Cleanest lakes in Campbell River County(6 lakes)
- Cleanest lakes in Victoria County(6 lakes)
- Cleanest lakes in Quesnel River County(5 lakes)
- Cleanest lakes in Lower Fraser County(5 lakes)
- Cleanest lakes in Cowichan County(5 lakes)
- Cleanest lakes in Parksville County(5 lakes)
Newfoundland and Labrador
- Cleanest lakes in Terra Nova County(9 lakes)
- Cleanest lakes in Newfoundland County(6 lakes)
- Cleanest lakes in Labrador County(2 lakes)
Topics & Definitions
Lake-Specific Answers
Every 3,147 answerable lake has dedicated Q&A pages: swim safety and cleanliness for all of them, plus fish species, pollution status and name confusion where the data supports it. Featured lakes below — search the full set on any lake page or the search page.
Rainy Lake
Koochiching County, Minnesota
Mille Lacs Lake
Aitkin County, Minnesota
Upper Red Lake
Beltrami County, Minnesota
Kabekona Bay Lake
Cass County, Minnesota
Steamboat Bay Lake
Cass County, Minnesota
Lake Winnibigoshish
Cass County, Minnesota
Tamarack Bay Lake
Cass County, Minnesota
Third River Flowage Lake
Itasca County, Minnesota
East Vermilion Lake
St. Louis County, Minnesota
West Vermilion Lake
St. Louis County, Minnesota