Lake Water Quality Answers
Direct answers to the questions people most often ask about lakes across our 36 covered states. Each answer pulls from EPA water quality data, Metropolitan Council grading methodology, 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
South Dakota
Florida
Colorado
North Carolina
Vermont
Oregon
Arkansas
Oklahoma
Kansas
Nebraska
Nevada
Arizona
Montana
New Mexico
Tennessee
Alabama
Virginia
Kentucky
Washington
Wyoming
Georgia
Cleanest Lakes by County
Top counties by lake count in each state. See all 1319 counties →
Minnesota
- Cleanest lakes in St. Louis County(208 lakes)
- Cleanest lakes in Lake County(152 lakes)
- Cleanest lakes in Itasca County(146 lakes)
- Cleanest lakes in Cass County(130 lakes)
- Cleanest lakes in Cook County(126 lakes)
- Cleanest lakes in Crow Wing County(121 lakes)
- Cleanest lakes in Hennepin County(104 lakes)
- Cleanest lakes in Becker County(102 lakes)
Wisconsin
- Cleanest lakes in Vilas County(191 lakes)
- Cleanest lakes in Oneida County(133 lakes)
- Cleanest lakes in Polk County(74 lakes)
- Cleanest lakes in Oconto County(60 lakes)
- Cleanest lakes in Burnett County(57 lakes)
- Cleanest lakes in Bayfield County(51 lakes)
- Cleanest lakes in Sawyer County(49 lakes)
- Cleanest lakes in Washburn County(46 lakes)
Illinois
- Cleanest lakes in Cook County(61 lakes)
- Cleanest lakes in Lake County(15 lakes)
- Cleanest lakes in Marion County(6 lakes)
- Cleanest lakes in McHenry County(5 lakes)
- Cleanest lakes in Macoupin County(3 lakes)
- Cleanest lakes in Randolph County(3 lakes)
- Cleanest lakes in Richland County(3 lakes)
- Cleanest lakes in Wayne County(3 lakes)
Michigan
- Cleanest lakes in Iron County(36 lakes)
- Cleanest lakes in Oakland County(35 lakes)
- Cleanest lakes in Gogebic County(35 lakes)
- Cleanest lakes in Benzie County(31 lakes)
- Cleanest lakes in Kalkaska County(22 lakes)
- Cleanest lakes in Cass County(20 lakes)
- Cleanest lakes in Livingston County(19 lakes)
- Cleanest lakes in Charlevoix County(18 lakes)
Iowa
- Cleanest lakes in Dickinson County(8 lakes)
- Cleanest lakes in Polk County(8 lakes)
- Cleanest lakes in Black Hawk County(7 lakes)
- Cleanest lakes in Union County(6 lakes)
- Cleanest lakes in Scott County(5 lakes)
- Cleanest lakes in Adair County(5 lakes)
- Cleanest lakes in Cerro Gordo County(4 lakes)
- Cleanest lakes in Hardin County(4 lakes)
Ohio
- Cleanest lakes in Warren County(4 lakes)
- Cleanest lakes in Clark County(4 lakes)
- Cleanest lakes in Harrison County(2 lakes)
- Cleanest lakes in Richland County(2 lakes)
- Cleanest lakes in Lawrence County(1 lakes)
- Cleanest lakes in Carroll County(1 lakes)
- Cleanest lakes in Ashland County(1 lakes)
- Cleanest lakes in Noble County(1 lakes)
Pennsylvania
- Cleanest lakes in Pike County(1 lakes)
- Cleanest lakes in Wyoming County(1 lakes)
- Cleanest lakes in Bucks County(1 lakes)
New York
- Cleanest lakes in Chautauqua County(14 lakes)
- Cleanest lakes in Putnam County(13 lakes)
- Cleanest lakes in Warren County(9 lakes)
- Cleanest lakes in Essex County(9 lakes)
- Cleanest lakes in Franklin County(9 lakes)
- Cleanest lakes in Madison County(8 lakes)
- Cleanest lakes in Herkimer County(7 lakes)
- Cleanest lakes in Fulton County(7 lakes)
Missouri
- Cleanest lakes in Jackson County(27 lakes)
- Cleanest lakes in Warren County(16 lakes)
- Cleanest lakes in Stone County(13 lakes)
- Cleanest lakes in Boone County(11 lakes)
- Cleanest lakes in Taney County(10 lakes)
- Cleanest lakes in Clay County(9 lakes)
- Cleanest lakes in St. Louis County(9 lakes)
- Cleanest lakes in Hickory County(8 lakes)
Indiana
- Cleanest lakes in Kosciusko County(14 lakes)
- Cleanest lakes in Lake County(2 lakes)
- Cleanest lakes in Monroe County(2 lakes)
- Cleanest lakes in Steuben County(1 lakes)
- Cleanest lakes in Marshall County(1 lakes)
- Cleanest lakes in Johnson County(1 lakes)
- Cleanest lakes in Starke County(1 lakes)
North Dakota
- Cleanest lakes in Rolette County(14 lakes)
- Cleanest lakes in Williams County(9 lakes)
- Cleanest lakes in Nelson County(9 lakes)
- Cleanest lakes in Ramsey County(8 lakes)
- Cleanest lakes in Stutsman County(7 lakes)
- Cleanest lakes in Grant County(6 lakes)
- Cleanest lakes in Mountrail County(5 lakes)
- Cleanest lakes in Benson County(4 lakes)
South Dakota
- Cleanest lakes in Roberts County(2 lakes)
- Cleanest lakes in Pennington County(1 lakes)
- Cleanest lakes in Charles Mix County(1 lakes)
Colorado
- Cleanest lakes in Larimer County(7 lakes)
- Cleanest lakes in Grand County(6 lakes)
- Cleanest lakes in La Plata County(4 lakes)
- Cleanest lakes in Jackson County(4 lakes)
- Cleanest lakes in Delta County(4 lakes)
- Cleanest lakes in Weld County(4 lakes)
- Cleanest lakes in Lake County(3 lakes)
- Cleanest lakes in Rio Blanco County(3 lakes)
North Carolina
- Cleanest lakes in Wake County(14 lakes)
- Cleanest lakes in Orange County(7 lakes)
- Cleanest lakes in Chatham County(7 lakes)
- Cleanest lakes in Gaston County(5 lakes)
- Cleanest lakes in Yadkin County(5 lakes)
- Cleanest lakes in Randolph County(5 lakes)
- Cleanest lakes in Bladen County(5 lakes)
- Cleanest lakes in Guilford County(5 lakes)
Vermont
- Cleanest lakes in Rutland County(30 lakes)
- Cleanest lakes in Orleans County(30 lakes)
- Cleanest lakes in Caledonia County(23 lakes)
- Cleanest lakes in Windsor County(21 lakes)
- Cleanest lakes in Windham County(19 lakes)
- Cleanest lakes in Essex County(19 lakes)
- Cleanest lakes in Washington County(17 lakes)
- Cleanest lakes in Bennington County(16 lakes)
Texas
- Cleanest lakes in Tom Green County(6 lakes)
- Cleanest lakes in Denton County(5 lakes)
- Cleanest lakes in Hill County(5 lakes)
- Cleanest lakes in Harris County(5 lakes)
- Cleanest lakes in Smith County(4 lakes)
- Cleanest lakes in Marion County(4 lakes)
- Cleanest lakes in Comal County(3 lakes)
- Cleanest lakes in Val Verde County(3 lakes)
Oregon
- Cleanest lakes in Klamath County(17 lakes)
- Cleanest lakes in Jefferson County(10 lakes)
- Cleanest lakes in Deschutes County(9 lakes)
- Cleanest lakes in Jackson County(7 lakes)
- Cleanest lakes in Baker County(4 lakes)
- Cleanest lakes in Lane County(3 lakes)
- Cleanest lakes in Douglas County(3 lakes)
- Cleanest lakes in Umatilla County(3 lakes)
Arkansas
- Cleanest lakes in Benton County(13 lakes)
- Cleanest lakes in Washington County(11 lakes)
- Cleanest lakes in Pulaski County(9 lakes)
- Cleanest lakes in Garland County(8 lakes)
- Cleanest lakes in Sharp County(6 lakes)
- Cleanest lakes in Chicot County(6 lakes)
- Cleanest lakes in Carroll County(4 lakes)
- Cleanest lakes in Ashley County(4 lakes)
Oklahoma
- Cleanest lakes in Kay County(6 lakes)
- Cleanest lakes in Cleveland County(5 lakes)
- Cleanest lakes in Seminole County(3 lakes)
- Cleanest lakes in Osage County(3 lakes)
- Cleanest lakes in Pottawatomie County(2 lakes)
- Cleanest lakes in Delaware County(2 lakes)
- Cleanest lakes in Caddo County(2 lakes)
- Cleanest lakes in Pushmataha County(2 lakes)
Kansas
- Cleanest lakes in Johnson County(17 lakes)
- Cleanest lakes in Linn County(9 lakes)
- Cleanest lakes in Sedgwick County(6 lakes)
- Cleanest lakes in Greenwood County(5 lakes)
- Cleanest lakes in Woodson County(5 lakes)
- Cleanest lakes in Miami County(5 lakes)
- Cleanest lakes in Douglas County(5 lakes)
- Cleanest lakes in Osage County(5 lakes)
Nebraska
- Cleanest lakes in Douglas County(6 lakes)
- Cleanest lakes in Cherry County(4 lakes)
- Cleanest lakes in Lincoln County(3 lakes)
- Cleanest lakes in Saunders County(3 lakes)
- Cleanest lakes in Dakota County(2 lakes)
- Cleanest lakes in Dawes County(2 lakes)
- Cleanest lakes in Gosper County(2 lakes)
- Cleanest lakes in Keith County(2 lakes)
Nevada
- Cleanest lakes in Washoe County(13 lakes)
- Cleanest lakes in Elko County(11 lakes)
- Cleanest lakes in Humboldt County(6 lakes)
- Cleanest lakes in Clark County(5 lakes)
- Cleanest lakes in Churchill County(4 lakes)
- Cleanest lakes in Lyon County(4 lakes)
- Cleanest lakes in Douglas County(3 lakes)
- Cleanest lakes in White Pine County(2 lakes)
Arizona
- Cleanest lakes in Coconino County(14 lakes)
- Cleanest lakes in Maricopa County(9 lakes)
- Cleanest lakes in Apache County(8 lakes)
- Cleanest lakes in Yavapai County(7 lakes)
- Cleanest lakes in Navajo County(4 lakes)
- Cleanest lakes in Pima County(4 lakes)
- Cleanest lakes in Mohave County(4 lakes)
- Cleanest lakes in Graham County(2 lakes)
Idaho
- Cleanest lakes in Valley County(9 lakes)
- Cleanest lakes in Kootenai County(5 lakes)
- Cleanest lakes in Bonneville County(5 lakes)
- Cleanest lakes in Power County(5 lakes)
- Cleanest lakes in Bear Lake County(4 lakes)
- Cleanest lakes in Elmore County(4 lakes)
- Cleanest lakes in Canyon County(2 lakes)
- Cleanest lakes in Blaine County(2 lakes)
Montana
- Cleanest lakes in Flathead County(75 lakes)
- Cleanest lakes in Missoula County(43 lakes)
- Cleanest lakes in Lake County(26 lakes)
- Cleanest lakes in Lincoln County(17 lakes)
- Cleanest lakes in Lewis and Clark County(11 lakes)
- Cleanest lakes in Carbon County(3 lakes)
- Cleanest lakes in Broadwater County(3 lakes)
- Cleanest lakes in Beaverhead County(2 lakes)
New Mexico
- Cleanest lakes in Rio Arriba County(13 lakes)
- Cleanest lakes in Otero County(4 lakes)
- Cleanest lakes in San Juan County(4 lakes)
- Cleanest lakes in Eddy County(4 lakes)
- Cleanest lakes in Lincoln County(4 lakes)
- Cleanest lakes in Quay County(3 lakes)
- Cleanest lakes in Chaves County(3 lakes)
- Cleanest lakes in San Miguel County(3 lakes)
Tennessee
- Cleanest lakes in Hamilton County(4 lakes)
- Cleanest lakes in Roane County(4 lakes)
- Cleanest lakes in Hawkins County(4 lakes)
- Cleanest lakes in Shelby County(4 lakes)
- Cleanest lakes in Meigs County(3 lakes)
- Cleanest lakes in Stewart County(3 lakes)
- Cleanest lakes in Davidson County(3 lakes)
- Cleanest lakes in Rhea County(2 lakes)
Alabama
- Cleanest lakes in Tuscaloosa County(7 lakes)
- Cleanest lakes in Tallapoosa County(3 lakes)
- Cleanest lakes in Elmore County(3 lakes)
- Cleanest lakes in Randolph County(3 lakes)
- Cleanest lakes in Covington County(3 lakes)
- Cleanest lakes in Wilcox County(3 lakes)
- Cleanest lakes in Lauderdale County(3 lakes)
- Cleanest lakes in Sumter County(3 lakes)
Virginia
- Cleanest lakes in Franklin County(12 lakes)
- Cleanest lakes in Pulaski County(8 lakes)
- Cleanest lakes in Bedford County(6 lakes)
- Cleanest lakes in Stafford County(6 lakes)
- Cleanest lakes in Spotsylvania County(6 lakes)
- Cleanest lakes in Amherst County(5 lakes)
- Cleanest lakes in Patrick County(4 lakes)
- Cleanest lakes in Chesterfield County(4 lakes)
Kentucky
- Cleanest lakes in Ballard County(8 lakes)
- Cleanest lakes in Christian County(4 lakes)
- Cleanest lakes in Ohio County(3 lakes)
- Cleanest lakes in Hopkins County(3 lakes)
- Cleanest lakes in Logan County(3 lakes)
- Cleanest lakes in Grant County(3 lakes)
- Cleanest lakes in Madison County(3 lakes)
- Cleanest lakes in Laurel County(2 lakes)
Utah
- Cleanest lakes in Daggett County(14 lakes)
- Cleanest lakes in Wasatch County(14 lakes)
- Cleanest lakes in Box Elder County(13 lakes)
- Cleanest lakes in Summit County(12 lakes)
- Cleanest lakes in Utah County(11 lakes)
- Cleanest lakes in Uintah County(10 lakes)
- Cleanest lakes in Garfield County(8 lakes)
- Cleanest lakes in Rich County(7 lakes)
Washington
- Cleanest lakes in Pierce County(8 lakes)
- Cleanest lakes in Thurston County(8 lakes)
- Cleanest lakes in Snohomish County(6 lakes)
- Cleanest lakes in Grant County(5 lakes)
- Cleanest lakes in Grays Harbor County(2 lakes)
- Cleanest lakes in Ferry County(2 lakes)
- Cleanest lakes in King County(2 lakes)
- Cleanest lakes in Clark County(2 lakes)
Wyoming
- Cleanest lakes in Fremont County(34 lakes)
- Cleanest lakes in Carbon County(27 lakes)
- Cleanest lakes in Albany County(21 lakes)
- Cleanest lakes in Park County(19 lakes)
- Cleanest lakes in Platte County(15 lakes)
- Cleanest lakes in Lincoln County(13 lakes)
- Cleanest lakes in Sweetwater County(13 lakes)
- Cleanest lakes in Teton County(12 lakes)
Georgia
- Cleanest lakes in Harris County(4 lakes)
- Cleanest lakes in Hall County(4 lakes)
- Cleanest lakes in Troup County(3 lakes)
- Cleanest lakes in Forsyth County(3 lakes)
- Cleanest lakes in Dougherty County(2 lakes)
- Cleanest lakes in Rabun County(2 lakes)
- Cleanest lakes in Union County(2 lakes)
- Cleanest lakes in Greene County(2 lakes)
Massachusetts
- Cleanest lakes in Worcester County(24 lakes)
- Cleanest lakes in Plymouth County(15 lakes)
- Cleanest lakes in Middlesex County(14 lakes)
- Cleanest lakes in Barnstable County(12 lakes)
- Cleanest lakes in Berkshire County(7 lakes)
- Cleanest lakes in Essex County(7 lakes)
- Cleanest lakes in Franklin County(5 lakes)
- Cleanest lakes in Hampshire County(4 lakes)
Topics & Definitions
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Lake-Specific Answers
Every 1,000 answerable lake has three dedicated Q&A pages: swim safety, cleanliness, and (where data exists) fish species. Featured lakes below — search the full set on any lake page or the search page.