Impaired Lakes in Wisconsin
519 of 1,449 graded Wisconsin lakes (36%) are officially listed as impaired under Clean Water Act §303(d) in the most recent EPA ATTAINS reporting cycle. 75 have an approved TMDL restoration plan.
Top Causes of Impairment in Wisconsin
297
Nutrients (phosphorus, nitrogen)
135
Mercury
89
Cause unknown
26
PCBs
16
Metals (other than mercury)
15
Turbidity
13
Pathogens (E. coli, fecal)
5
PFAS
All 519 EPA-Listed Impaired Lakes in Wisconsin
| Lake | County | Grade | Causes | TMDL |
|---|---|---|---|---|
| Round Lake | Waupaca | A | Nutrients (phosphorus, nitrogen) | — |
| Beasley Lake | Waupaca | A | Nutrients (phosphorus, nitrogen) | — |
| Clear Lake | Oneida | A | Mercury | — |
| Sugar Camp Lake | Oneida | A | Mercury | — |
| Pike Lake | Polk | A | Nutrients (phosphorus, nitrogen) | — |
| Hemlock Lake | Oneida | A | Mercury | — |
| White Lake | Oconto | A | Nutrients (phosphorus, nitrogen) | — |
| Alva Lake | Oneida | A | Mercury | — |
| Franklin Lake | Oneida | A | Mercury | — |
| Sand Lake | Rusk | A | Mercury | — |
| Crystal Lake | Bayfield | A | Mercury | — |
| Crystal Lake | Sheboygan | A | Mercury | — |
| Perch Lake | Oneida | A | Mercury | — |
| White Birch Lake | Vilas | A | Mercury | — |
| Paddock Lake | Kenosha | A | Nutrients (phosphorus, nitrogen) | — |
| Sunset Lake | Vilas | A | Nutrients (phosphorus, nitrogen) | — |
| Ballard Lake | Vilas | A | Mercury | — |
| Moose Lake | Waukesha | A | Nutrients (phosphorus, nitrogen) | — |
| Mary Lake | Lincoln | A | Mercury | — |
| Dorothy Lake | Oneida | A | Mercury | — |
| Bird Lake | Oneida | A | Mercury | — |
| Buffalo Lake | Oneida | A | Nutrients (phosphorus, nitrogen) | — |
| Clear Lake | Rock | A | Cause unknown | — |
| Pope Lake | Waupaca | A | Nutrients (phosphorus, nitrogen) | — |
| Middle Mckenzie Lake | Burnett | A | Nutrients (phosphorus, nitrogen) | — |
| Clara Lake-Deep Hole | Lincoln | A | Mercury | — |
| Hodstradt Lake | Oneida | A | Mercury | — |
| Arbutus Lake | Forest | A | Cause unknown | — |
| Lake Buteau | Lincoln | A | Mercury | — |
| Slim Lake | Washburn | A | Nutrients (phosphorus, nitrogen) | — |
| Hewitt Lake | Iron | A | Mercury | — |
| Okauchee Lake-Site No. 4-at Okauchee | Waukesha | A | Nutrients (phosphorus, nitrogen) | — |
| Okauchee Lake-Site No. 3-at Okauchee | Waukesha | A | Nutrients (phosphorus, nitrogen) | — |
| Day Lake | Vilas | A | Mercury | — |
| Round Lake Northeast Site | Chippewa | A | Mercury | — |
| Nc Cheq Bay Lake | Ashland | A | Toxic organics | — |
| Trego Lake | Washburn | A | Cause unknown | — |
| Tambling Lake | Vilas | A | Cause unknown | — |
| Greater Bass Lake | Langlade | A | Mercury | — |
| Lac Courte Oreilles Lake | Sawyer | A | Cause unknown | — |
| Whitefish Lake | Sawyer | A | Mercury | — |
| Big Cedar Lake-South Site-Near West Bend | Washington | A | Cause unknown | — |
| Lake Beulah Station 2 | Walworth | A | Nutrients (phosphorus, nitrogen) | — |
| Lake Beulah | Walworth | A | Nutrients (phosphorus, nitrogen) | — |
| Okauchee Lake | Waukesha | A | Nutrients (phosphorus, nitrogen) | — |
| Oconomowoc Lake 2 | Waukesha | A | Nutrients (phosphorus, nitrogen) | — |
| Spider Lake | Vilas | A | Nutrients (phosphorus, nitrogen) | — |
| Silver Lake | Barron | A | Mercury | — |
| Silver Lake | Vilas | A | Cause unknown | — |
| Round Lake | Shawano | A | Cause unknown | ✓ |
| Mirror Lake | Waupaca | A | Cause unknown | — |
| Bass Lake | Vilas | A | Cause unknown | — |
| Bass Lake | Lincoln | A | Mercury | — |
| Clear Lake | Rusk | A | Nutrients (phosphorus, nitrogen) | — |
| Marl Lake | Waupaca | A | Nutrients (phosphorus, nitrogen) | — |
| Indian Lake | Oneida | A | Mercury | — |
| Long Lake | Waupaca | A | Nutrients (phosphorus, nitrogen) | — |
| Long Lake | Lincoln | A | Mercury | — |
| Crescent Lake | Oneida | A | Mercury | — |
| Red Cedar Lake | Barron | A | Nutrients (phosphorus, nitrogen) | — |
| Shadow Lake | Waupaca | A | Cause unknown | — |
| Pipe Lake | Polk | A | Mercury | — |
| Armour Lake | Vilas | A | Mercury | — |
| Big Dummy Lake | Barron | A | Nutrients (phosphorus, nitrogen) | — |
| Diamond Lake | Bayfield | A | Mercury | — |
| Church Pine Lake | Polk | A | Nutrients (phosphorus, nitrogen) | — |
| Echo Lake | Barron | A | Cause unknown | — |
| Wind Lake | Polk | A | Nutrients (phosphorus, nitrogen) | — |
| Oconomowoc Lake Site | Waukesha | A | Nutrients (phosphorus, nitrogen) | — |
| Meta Lake | Vilas | A | Cause unknown | — |
| Forest Lake | Fond du Lac | A | Mercury, Nutrients (phosphorus, nitrogen) | — |
| Turtle Lake | Walworth | A | Cause unknown | — |
| Horsehead Lake | Vilas | A | Mercury, Nutrients (phosphorus, nitrogen) | — |
| Maple Lake | Oneida | A | Mercury | — |
| Windigo Lake | Sawyer | A | Mercury | — |
| Korth Lake | Shawano | A | Cause unknown | — |
| Lynx Lake | Vilas | A | Mercury | — |
| Seven Island Lake | Lincoln | A | Mercury | — |
| Snipe Lake | Vilas | A | Mercury | — |
| Pine Lake | Shawano | A | Cause unknown | ✓ |
| Moon Lake | Vilas | A | Nutrients (phosphorus, nitrogen) | — |
| Spirit Lake | Oneida | A | Mercury | — |
| Fowler Lake | Waukesha | A | Nutrients (phosphorus, nitrogen), PCBs | — |
| Columbia Lake | Waupaca | A | Nutrients (phosphorus, nitrogen) | — |
| Gilmore Lake | Washburn | A | Nutrients (phosphorus, nitrogen) | — |
| Elkhart Lake | Sheboygan | A | Mercury | — |
| Lake Beulah | Walworth | A | Nutrients (phosphorus, nitrogen) | — |
| Alma Lake | Vilas | A | Nutrients (phosphorus, nitrogen) | — |
| Axhandle Lake | Chippewa | A | Mercury | — |
| Irving Lake | Vilas | A | Mercury | — |
| Tuma Lake | Manitowoc | A | Nutrients (phosphorus, nitrogen) | ✓ |
| Finger Lake | Vilas | A | Cause unknown | — |
| Antler Lake | Polk | A | Nutrients (phosphorus, nitrogen) | — |
| Okauchee Lake | Waukesha | A | Nutrients (phosphorus, nitrogen) | — |
| Hunter Lake | Vilas | A | Nutrients (phosphorus, nitrogen) | — |
| Lone Stone Lake | Oneida | A | Mercury | — |
| Big Mckenzie Lake | Washburn | A | Nutrients (phosphorus, nitrogen) | — |
| De Neveu Lake | Fond du Lac | A | Nutrients (phosphorus, nitrogen) | — |
| Upper Gresham Lake | Vilas | A | Mercury | — |
| Little Dummy Lake | Barron | A | Nutrients (phosphorus, nitrogen) | — |
| Little Cedar Lake | Washington | A | Cause unknown | — |
| Hilbert Lake | Marinette | A | Cause unknown | — |
| Taylor Lake | Waupaca | A | Nutrients (phosphorus, nitrogen) | ✓ |
| Sand Lake | Sawyer | B | Mercury | — |
| Green Lake | Green Lake | B | Nutrients (phosphorus, nitrogen) | ✓ |
| Spider Lake | Iron | B | Mercury | — |
| Pickerel Lake | Forest | B | Cause unknown | — |
| Pickerel Lake | Portage | B | Nutrients (phosphorus, nitrogen) | — |
| Pickerel Lake | Lincoln | B | Mercury | — |
| North Turtle Lake | Vilas | B | Nutrients (phosphorus, nitrogen) | — |
| Balsam Lake | Washburn | B | Nutrients (phosphorus, nitrogen) | — |
| Whitefish Lake | Oneida | B | Mercury | — |
| Round Lake | Chippewa | B | Mercury | — |
| Round Lake | Polk | B | Nutrients (phosphorus, nitrogen) | — |
| Cedar Lake | Iron | B | Mercury | — |
| Deep Lake | Washburn | B | Nutrients (phosphorus, nitrogen) | — |
| Bass Lake | Price | B | Mercury | — |
| Bass Lake | Barron | B | Nutrients (phosphorus, nitrogen) | — |
| Pioneer Lake | Vilas | B | Nutrients (phosphorus, nitrogen) | — |
| Oxbow Lake | Vilas | B | Mercury, Nutrients (phosphorus, nitrogen) | — |
| Long Lake | Washburn | B | Nutrients (phosphorus, nitrogen) | — |
| Long Lake | Oneida | B | Mercury | — |
| North Lake | Waukesha | B | Nutrients (phosphorus, nitrogen) | — |
| Camelot Lake | Adams | B | Cause unknown | — |
| Stone Lake | Vilas | B | Nutrients (phosphorus, nitrogen) | — |
| Grass Lake | Shawano | B | Cause unknown | ✓ |
| Island Lake | Vilas | B | Nutrients (phosphorus, nitrogen) | — |
| Saint Croix Flowage Lake | Douglas | B | Mercury | — |
| Little Sand Lake | Forest | B | Mercury | — |
| Walsh Lake | Forest | B | Mercury | — |
| Little Pine Lake | Iron | B | Mercury | — |
| Tahkodah Lake | Bayfield | B | Mercury | — |
| Sand Lake | Barron | B | Cause unknown | — |
| Sand Lake | Iron | B | Mercury | — |
| Sand Lake | Florence | B | Mercury | — |
| Annabelle Lake | Vilas | B | Mercury | — |
| Lower Vermillion Lake | Barron | B | Cause unknown | — |
| Schnur Lake | Price | B | Mercury, Nutrients (phosphorus, nitrogen) | — |
| Beaver Lake | Chippewa | B | Nutrients (phosphorus, nitrogen) | — |
| Pensaukee Lake | Shawano | B | Nutrients (phosphorus, nitrogen) | ✓ |
| Youngs Lake Waupaca Co | Waupaca | B | Nutrients (phosphorus, nitrogen) | — |
| Virgin Lake | Oneida | B | Mercury | — |
| Lake Nebagamon | Douglas | B | Mercury | — |
| Otter Lake | Waupaca | B | Nutrients (phosphorus, nitrogen) | ✓ |
| Big Moon Lake at | Barron | B | Nutrients (phosphorus, nitrogen) | — |
| Porcupine Lake | Oconto | B | Nutrients (phosphorus, nitrogen) | — |
| Hill Lake | Oneida | B | Nutrients (phosphorus, nitrogen) | ✓ |
| Camelot Lake | Adams | B | Cause unknown | — |
| Durphee Lake | Sawyer | B | Cause unknown | — |
| Lake Julia | Oneida | B | Mercury | — |
| Freedom Lakes | Polk | B | Nutrients (phosphorus, nitrogen) | — |
| Lamont Lake | Polk | B | Nutrients (phosphorus, nitrogen) | — |
| Lower Phantom Lake | Waukesha | B | Nutrients (phosphorus, nitrogen) | — |
| Shannon Lake | Vilas | B | Mercury | — |
| Hidden Valley Lake 1 | Lafayette | B | Nutrients (phosphorus, nitrogen) | — |
| Mccullough Lake | Vilas | B | Cause unknown | — |
| Dads Lake | Vilas | B | Cause unknown | — |
| Big Cedar Lake | Washington | B | Cause unknown | — |
| Army Lake | Walworth | B | Nutrients (phosphorus, nitrogen) | — |
| Long Lake -Spread Eagle Chain | Florence | B | Mercury | — |
| Little Carr Lake | Oneida | B | Mercury | — |
| Big Carr Lake | Oneida | B | Mercury | — |
| Green Lake | Green Lake | B | Nutrients (phosphorus, nitrogen) | ✓ |
| Cross Lake | Kenosha | B | Nutrients (phosphorus, nitrogen) | — |
| Morton Lake | Vilas | B | Cause unknown | — |
| Prong Lake | Vilas | B | Nutrients (phosphorus, nitrogen) | — |
| Mcnutt Lake | Oneida | B | Nutrients (phosphorus, nitrogen) | ✓ |
| Oneonta Lake | Marinette | B | Cause unknown | — |
| Okauchee Lake-Site No. 1-Near Okauchee | Waukesha | B | Nutrients (phosphorus, nitrogen) | — |
| L St Germain Lk Site K @ S. Bay Lake | Vilas | B | Nutrients (phosphorus, nitrogen) | — |
| Siskiwit Lake | Bayfield | B | Mercury | — |
| Delavan Lake | Walworth | B | Nutrients (phosphorus, nitrogen) | — |
| Little Rice Lake | Forest | B | Mercury | — |
| Siskiwit Lake | Bayfield | B | Mercury | — |
| East Wetland Inlet To Lake Ree | Bayfield | B | Mercury | — |
| Calkins Lake | Chippewa | B | Mercury | — |
| Dace Lake | Polk | B | Cause unknown | — |
| Green Lake | Green Lake | B | Nutrients (phosphorus, nitrogen) | ✓ |
| Delavan Lake | Walworth | B | Nutrients (phosphorus, nitrogen) | — |
| Delavan Lake | Walworth | B | Nutrients (phosphorus, nitrogen) | — |
| Green Lake | Green Lake | B | Nutrients (phosphorus, nitrogen) | ✓ |
| Okauchee Lake-Site No. 2-at Okauchee | Waukesha | B | Nutrients (phosphorus, nitrogen) | — |
| Lake St. Croix | St. Croix | B | Nutrients (phosphorus, nitrogen) | ✓ |
| Balsam Lake | Polk | B | Cause unknown | — |
| Silver Lake | Columbia | B | Mercury, Metals (other than mercury), PCBs | — |
| Little Friess Lake | Washington | B | Cause unknown | — |
| Bone Lake | Polk | B | Nutrients (phosphorus, nitrogen) | — |
| Turtle Flambeau Flowage Lake | Iron | B | Mercury, Nutrients (phosphorus, nitrogen) | — |
| Bear Lake | Forest | B | Cause unknown | — |
| Bear Lake | Barron | B | Nutrients (phosphorus, nitrogen) | — |
| Crescent Lake | Polk | B | Nutrients (phosphorus, nitrogen) | — |
| Rainbow Lake | Vilas | B | Nutrients (phosphorus, nitrogen) | — |
| Island Lake | Oneida | B | Mercury | — |
| Big Lake | Polk | B | Nutrients (phosphorus, nitrogen) | — |
| Lac la Belle Lake | Waukesha | B | Nutrients (phosphorus, nitrogen), PCBs | — |
| Mid Lake | Oneida | B | Mercury | — |
| Mcdonald Lake | Vilas | B | Nutrients (phosphorus, nitrogen) | — |
| Bahr Lake | Shawano | B | Cause unknown | — |
| Crane Lake | Forest | B | Cause unknown | — |
| Horseshoe Lake | Polk | B | Cause unknown | — |
| Auburn Lake | Fond du Lac | B | Mercury, Nutrients (phosphorus, nitrogen) | — |
| Spring Lake | Portage | B | Nutrients (phosphorus, nitrogen) | ✓ |
| St Croix Flowage Lake | Douglas | B | Mercury | — |
| Beaver Lake | Vilas | B | Cause unknown | — |
| Robinson Pond | Jackson | B | Mercury | — |
| Pine Lake | Iron | B | Mercury | — |
| Lipsett Lake | Burnett | B | Cause unknown | — |
| Lake Minnesuing | Douglas | B | Mercury | — |
| Loveless Lake | Polk | B | Nutrients (phosphorus, nitrogen) | — |
| Big Bass Lake | Marathon | B | Mercury | — |
| Bear Trap Lake | Polk | B | Cause unknown | — |
| English Lake | Manitowoc | B | Nutrients (phosphorus, nitrogen) | ✓ |
| Clarey Lake | Polk | B | Nutrients (phosphorus, nitrogen) | — |
| Van Zile Lake | Forest | B | Mercury | — |
| Silver Lake West Basin | Columbia | B | Mercury, Metals (other than mercury), PCBs | — |
| Black Hawk Lake | Iowa | B | Cause unknown | — |
| Lake Pesobic | Lincoln | B | Mercury | — |
| Oneida Lake | Oneida | B | Cause unknown | — |
| Little Bearskin Lake | Oneida | B | Cause unknown | — |
| Kasbaum Lake | Manitowoc | B | Nutrients (phosphorus, nitrogen) | ✓ |
| Moccasin Lake | Oneida | B | Mercury | — |
| Mckenzie Lake | Polk | B | Nutrients (phosphorus, nitrogen) | — |
| Lake Thirty | Barron | B | Nutrients (phosphorus, nitrogen) | — |
| Lake Content | Vilas | B | Nutrients (phosphorus, nitrogen) | — |
| Okauchee Lake Site | Waukesha | B | Nutrients (phosphorus, nitrogen) | — |
| Okauchee Lake Deep Hole Usgs | Waukesha | B | Nutrients (phosphorus, nitrogen) | — |
| Ocauchee Lake | Waukesha | B | Nutrients (phosphorus, nitrogen) | — |
| Delavan Lake | Walworth | C | Nutrients (phosphorus, nitrogen) | — |
| Pickerel Lake | Vilas | C | Cause unknown | — |
| Round Lake | Price | C | Nutrients (phosphorus, nitrogen) | — |
| Round Lake | Oneida | C | Mercury | — |
| Bass Lake | Oneida | C | Mercury | — |
| Townline Lake | Oneida | C | Mercury | — |
| Indian Lake | Oneida | C | Cause unknown | — |
| Milwaukee Harbor Lake | Milwaukee | C | Metals (other than mercury), Pathogens (E. coli, fecal), PCBs | ✓ |
| Long Lake | Polk | C | Nutrients (phosphorus, nitrogen) | — |
| Long Lake | Polk | C | Nutrients (phosphorus, nitrogen) | — |
| Long Lake | Shawano | C | Cause unknown | ✓ |
| Birch Lake | Oneida | C | Cause unknown | — |
| Birch Lake | Washburn | C | Nutrients (phosphorus, nitrogen) | — |
| Nelson Lake | Sawyer | C | Nutrients (phosphorus, nitrogen) | — |
| Dog Lake | Oneida | C | Mercury | — |
| Lakeshore State Park Fish Shocking | Milwaukee | C | Metals (other than mercury), Pathogens (E. coli, fecal), PCBs | ✓ |
| Rock Lake | Vilas | C | Nutrients (phosphorus, nitrogen) | — |
| Delavan Lake | Walworth | C | Nutrients (phosphorus, nitrogen) | — |
| Wolf Lake | Portage | C | Nutrients (phosphorus, nitrogen) | — |
| Green Lake | Green Lake | C | Nutrients (phosphorus, nitrogen) | ✓ |
| Fawn Lake | Vilas | C | Nutrients (phosphorus, nitrogen) | — |
| Mud Lake | Polk | C | Cause unknown | — |
| Deer Lake | Oneida | C | Mercury | — |
| Duck Lake | Langlade | C | Nutrients (phosphorus, nitrogen) | — |
| Big Arbor Vitae Lake | Vilas | C | Nutrients (phosphorus, nitrogen) | — |
| Little Sand Lake | Barron | C | Cause unknown | — |
| Bearskin Lake | Oneida | C | Cause unknown | — |
| Stella Lake | Vilas | C | Mercury | — |
| Lake Esadore | Taylor | C | Mercury | — |
| Amnicon Lake | Douglas | C | Cause unknown, Turbidity | — |
| Found Lake | Vilas | C | Cause unknown | — |
| Ward Lake | Polk | C | Nutrients (phosphorus, nitrogen) | — |
| Whitewater Lake | Walworth | C | Nutrients (phosphorus, nitrogen) | — |
| Laurel Lake | Oneida | C | Mercury, Nutrients (phosphorus, nitrogen) | — |
| West Horsehead Lake | Oneida | C | Mercury | — |
| Big Trade Lake | Burnett | C | Nutrients (phosphorus, nitrogen) | — |
| Wood Lake | Burnett | C | Nutrients (phosphorus, nitrogen) | — |
| Hancock Lake | Oneida | C | Cause unknown | — |
| White Mound Lake | Sauk | C | Cause unknown | — |
| Shawano Lake | Shawano | C | Nutrients (phosphorus, nitrogen) | ✓ |
| Bullhead Lake | Langlade | C | Nutrients (phosphorus, nitrogen) | — |
| Big Stone Lake | Oneida | C | Mercury, Nutrients (phosphorus, nitrogen) | — |
| Pine Lake | Forest | C | Cause unknown | — |
| Moon Lake | Barron | C | Nutrients (phosphorus, nitrogen) | — |
| Milwaukee Harbor Lake | Milwaukee | C | Metals (other than mercury), Pathogens (E. coli, fecal), PCBs | ✓ |
| Lake Sherwood | Adams | C | Cause unknown | — |
| Amacoy Lake | Rusk | C | Cause unknown | — |
| North Pipe Lake | Polk | C | Cause unknown | — |
| Milwaukee Harbor Lake | Milwaukee | C | Metals (other than mercury), Pathogens (E. coli, fecal), PCBs | ✓ |
| Enterprise Lake | Langlade | C | Cause unknown | — |
| Yellow Lake | Burnett | C | Nutrients (phosphorus, nitrogen) | — |
| Arrowhead Lake | Adams | C | Cause unknown | — |
| Collins Lake | Portage | C | Mercury, Nutrients (phosphorus, nitrogen) | ✓ |
| Granite Lake at | Barron | C | Cause unknown | — |
| Big Twin Lake | Green Lake | C | Nutrients (phosphorus, nitrogen) | ✓ |
| Tichigan Lake | Racine | C | PCBs | — |
| Red Bass Lake | Vilas | C | Nutrients (phosphorus, nitrogen) | — |
| Williams Lake | Marquette | C | PCBs | — |
| Easton Lake | Adams | C | Cause unknown | — |
| Voltz Lake | Kenosha | C | Nutrients (phosphorus, nitrogen) | — |
| Mineral Lake | Ashland | C | Nutrients (phosphorus, nitrogen) | — |
| Poskin Lake | Barron | C | Nutrients (phosphorus, nitrogen) | — |
| Swan Lake | Walworth | C | Nutrients (phosphorus, nitrogen) | — |
| High Falls Reservoir at | Marinette | C | Mercury | — |
| Twin Falls Flowage Us Twin Falls Dam Lake | Florence | C | Mercury | — |
| Little Fork Lake | Oneida | C | Mercury | — |
| Smith Lake | Vilas | C | Nutrients (phosphorus, nitrogen) | — |
| Range Line Lake | Vilas | C | Cause unknown | — |
| North Lake West Basin | Waukesha | C | Nutrients (phosphorus, nitrogen) | — |
| South Harper Lake | Taylor | C | Mercury | — |
| Little St. Germain Lk-South Bay-Nr St. Germain Lake | Vilas | C | Nutrients (phosphorus, nitrogen) | — |
| Lake Chetac North Basin | Sawyer | C | Nutrients (phosphorus, nitrogen) | — |
| Lake Lorraine | Walworth | C | Nutrients (phosphorus, nitrogen) | — |
| Potter Lake | Walworth | C | Nutrients (phosphorus, nitrogen) | — |
| Dowling Lake | Douglas | C | Cause unknown | — |
| Big Round Lake | Polk | C | Nutrients (phosphorus, nitrogen) | — |
| Potter Lake | Walworth | C | Nutrients (phosphorus, nitrogen) | — |
| Cranberry Lake | Oneida | C | Cause unknown | — |
| Round Lake | Burnett | C | Nutrients (phosphorus, nitrogen) | — |
| Cedar Lake | Polk | C | Nutrients (phosphorus, nitrogen) | ✓ |
| Rice Lake | Barron | C | Nutrients (phosphorus, nitrogen) | — |
| Rice Lake | Vilas | C | Nutrients (phosphorus, nitrogen) | — |
| Hidden Valley Lake | Lafayette | C | Nutrients (phosphorus, nitrogen) | — |
| Lake Alice | Lincoln | C | Oxygen depletion (low DO) | — |
| Cooley Lake | Oconto | C | Nutrients (phosphorus, nitrogen) | — |
| Butternut Lake | Price | C | Mercury, Nutrients (phosphorus, nitrogen) | — |
| Lake Puckaway | Green Lake | C | Cause unknown, Nutrients (phosphorus, nitrogen), Turbidity | ✓ |
| Lake Emily | Dodge | C | Nutrients (phosphorus, nitrogen) | ✓ |
| Loon Lake | Chippewa | C | Mercury | — |
| Hartlaub Lake | Manitowoc | C | Nutrients (phosphorus, nitrogen) | ✓ |
| Lake Desair | Barron | C | Nutrients (phosphorus, nitrogen), Turbidity | — |
| Lake Mohawksin | Lincoln | C | Oxygen depletion (low DO), PFAS | — |
| Little St Germain Lake | Vilas | C | Nutrients (phosphorus, nitrogen) | — |
| Porcupine Lake-Deep Hole | Oconto | C | Nutrients (phosphorus, nitrogen) | — |
| Lake Kegonsa | Dane | C | Nutrients (phosphorus, nitrogen), PFAS | ✓ |
| Milwaukee River Lake | Milwaukee | C | Metals (other than mercury), Pathogens (E. coli, fecal), PCBs | ✓ |
| Holcombe Flowage Lake | Chippewa | C | Nutrients (phosphorus, nitrogen), Turbidity | — |
| Fourmile Lake | Oneida | C | Mercury | — |
| White Clay Lake | Shawano | C | Nutrients (phosphorus, nitrogen) | ✓ |
| Friess Lake | Washington | C | Nutrients (phosphorus, nitrogen) | — |
| Horseshoe Lake | Manitowoc | C | Nutrients (phosphorus, nitrogen) | ✓ |
| Milwaukee Harbor North Half Lake | Milwaukee | C | Metals (other than mercury), Pathogens (E. coli, fecal), PCBs | ✓ |
| Milwaukee Harbor Lake | Milwaukee | C | Metals (other than mercury), Pathogens (E. coli, fecal), PCBs | ✓ |
| Upper Turtle Lake | Barron | C | Nutrients (phosphorus, nitrogen) | — |
| North Spirit Lake | Price | C | Cause unknown | — |
| Moose Lake | Sawyer | C | Mercury | — |
| Muskellunge Lake | Vilas | C | Cause unknown | — |
| Milwaukee Harbor Lake | Milwaukee | C | Metals (other than mercury), Pathogens (E. coli, fecal), PCBs | ✓ |
| Otter Lake | Vilas | C | Nutrients (phosphorus, nitrogen) | — |
| Lower Turtle Lake | Barron | C | Nutrients (phosphorus, nitrogen) | — |
| Lower Spring Lake | Jefferson | C | Nutrients (phosphorus, nitrogen) | — |
| Lost Lake | Vilas | C | Cause unknown | — |
| Harpt Lake | Manitowoc | C | Nutrients (phosphorus, nitrogen) | ✓ |
| North White Ash Lake | Polk | C | Nutrients (phosphorus, nitrogen) | — |
| Scattering Rice Lake | Vilas | C | Cause unknown | — |
| Mauthe Lake | Fond du Lac | C | Mercury, Nutrients (phosphorus, nitrogen) | — |
| Wapogasset Lake | Polk | C | Nutrients (phosphorus, nitrogen) | — |
| Camelia Lake | Polk | C | Nutrients (phosphorus, nitrogen) | — |
| Little Trade Lake | Burnett | C | Nutrients (phosphorus, nitrogen) | — |
| Schoenick Lake at | Shawano | C | Nutrients (phosphorus, nitrogen) | — |
| Lake Wingra | Dane | C | PCBs | — |
| Bakkens Pond | Sauk | C | Nutrients (phosphorus, nitrogen) | — |
| Little Arbor Vitae Lake | Vilas | C | Nutrients (phosphorus, nitrogen) | — |
| Lake Mendota | Dane | C | Nutrients (phosphorus, nitrogen) | ✓ |
| Little Blake Lake | Polk | C | Nutrients (phosphorus, nitrogen) | — |
| Magnor Lake | Polk | C | Nutrients (phosphorus, nitrogen) | — |
| Little Bass Lake | Polk | C | Nutrients (phosphorus, nitrogen) | — |
| Unnamed Rusk Co -Deep Hole Lake | Rusk | C | Mercury | — |
| Alexander Lake | Lincoln | C | Cause unknown | — |
| Hill Slough Lake | Sauk | C | Nutrients (phosphorus, nitrogen) | — |
| Lake Montanis | Barron | D | Nutrients (phosphorus, nitrogen) | — |
| Mccann Lake | Rusk | D | Nutrients (phosphorus, nitrogen) | — |
| Mirror Lake | Sauk | D | Nutrients (phosphorus, nitrogen) | — |
| Bass Lake | Burnett | D | Nutrients (phosphorus, nitrogen) | — |
| Clear Lake | Rock | D | Cause unknown | — |
| Rice Lake | Walworth | D | Nutrients (phosphorus, nitrogen) | — |
| Indian Lake | Langlade | D | Mercury | — |
| Little Butternut Lake | Polk | D | Nutrients (phosphorus, nitrogen) | — |
| Planting Ground Lake | Oneida | D | Mercury | — |
| Chain Lake | Chippewa | D | Mercury | — |
| Pike Lake | Price | D | Nutrients (phosphorus, nitrogen) | — |
| Turner Lake | Price | D | Nutrients (phosphorus, nitrogen) | — |
| Moen Lake | Oneida | D | Mercury | — |
| Mud Lake | Washburn | D | Nutrients (phosphorus, nitrogen) | — |
| Duck Lake | Vilas | D | Nutrients (phosphorus, nitrogen) | — |
| Boot Lake | Vilas | D | Cause unknown | — |
| Eagle Lake | Vilas | D | Cause unknown | — |
| Solberg Lake | Price | D | Mercury | — |
| Hat Rapids Flowage Lake | Oneida | D | Mercury | — |
| Emma Lake | Oneida | D | Mercury | — |
| Milwaukee Harbor South Half Lake | Milwaukee | D | Metals (other than mercury), Pathogens (E. coli, fecal), PCBs | ✓ |
| Milwaukee Harbor Lake | Milwaukee | D | Metals (other than mercury), Pathogens (E. coli, fecal), PCBs | ✓ |
| Crystal Lake | Oneida | D | Nutrients (phosphorus, nitrogen) | — |
| Lac Sault Dore Lake | Price | D | Nutrients (phosphorus, nitrogen) | — |
| Second Lake | Oneida | D | Mercury | — |
| Lake Mallalieu | St. Croix | D | Nutrients (phosphorus, nitrogen) | — |
| Deep Hole Lake | Langlade | D | Nutrients (phosphorus, nitrogen) | — |
| Lake Waubesa | Dane | D | Nutrients (phosphorus, nitrogen), PFAS | ✓ |
| Yellow Birch Lake | Vilas | D | Nutrients (phosphorus, nitrogen) | — |
| Third Lake | Oneida | D | Mercury | — |
| Upper Park Falls Flowage Lake | Price | D | Mercury, Metals (other than mercury) | — |
| Tug Lake | Lincoln | D | Mercury | — |
| Lynx Lake | Vilas | D | Nutrients (phosphorus, nitrogen) | — |
| Bullhead Lake | Manitowoc | D | Nutrients (phosphorus, nitrogen) | ✓ |
| Big Butternut Lake | Polk | D | Nutrients (phosphorus, nitrogen) | — |
| Gass Lake | Manitowoc | D | Nutrients (phosphorus, nitrogen) | ✓ |
| Vincent Lake | Polk | D | Nutrients (phosphorus, nitrogen) | — |
| Pelican Lake | Oneida | D | Cause unknown | — |
| Old Taylor Lake | Waupaca | D | Nutrients (phosphorus, nitrogen) | ✓ |
| Spirit River Flowage Lake | Lincoln | D | Mercury, Nutrients (phosphorus, nitrogen) | — |
| Amik Lake | Vilas | D | Nutrients (phosphorus, nitrogen) | — |
| Deep Hole Lake | Langlade | D | Nutrients (phosphorus, nitrogen) | — |
| Horse Lake | Polk | D | Nutrients (phosphorus, nitrogen) | — |
| Milwaukee Harbor Estuary Lake | Milwaukee | D | Metals (other than mercury), Pathogens (E. coli, fecal), PCBs | ✓ |
| Granite Lake South Basin | Barron | D | Cause unknown | — |
| Dowling Lake | Douglas | D | Cause unknown | — |
| Deep Hole Lake | Langlade | D | Nutrients (phosphorus, nitrogen) | — |
| Wilson Flowage Lake | Price | D | Nutrients (phosphorus, nitrogen) | — |
| Clam Lake | Burnett | D | Nutrients (phosphorus, nitrogen) | — |
| Lake Shangrila -Benet | Kenosha | D | Nutrients (phosphorus, nitrogen) | — |
| Moon Bay Lake | Chippewa | D | Nutrients (phosphorus, nitrogen) | — |
| Caldron Falls Reservoir | Marinette | D | Mercury | — |
| Dunn Lake | Vilas | D | Cause unknown | — |
| Largon Lake | Polk | D | Nutrients (phosphorus, nitrogen) | — |
| Lake Wissota | Chippewa | D | Nutrients (phosphorus, nitrogen), PCBs | — |
| Lake Monona | Dane | D | Nutrients (phosphorus, nitrogen), PFAS, PCBs | ✓ |
| Musser Lake | Price | D | Mercury, Nutrients (phosphorus, nitrogen) | — |
| Hallie Lake | Chippewa | D | Turbidity | — |
| Apple River Flowage Lake | Polk | D | Nutrients (phosphorus, nitrogen) | — |
| Ne Bay Lake | Vilas | D | Cause unknown | — |
| Turtle-Flambeau Flowage Lake | Iron | D | Mercury, Nutrients (phosphorus, nitrogen) | — |
| Swan Lake | Columbia | D | Cause unknown | ✓ |
| Seneca Lake | Vilas | D | Nutrients (phosphorus, nitrogen) | — |
| Lac la Belle Lake | Waukesha | D | Nutrients (phosphorus, nitrogen), PCBs | — |
| Sheas Lake | Kewaunee | D | Nutrients (phosphorus, nitrogen) | ✓ |
| Madeline Lake | Oneida | D | Mercury | — |
| Omer Lake | Polk | D | Nutrients (phosphorus, nitrogen) | — |
| Big Doctor Lake | Burnett | D | Nutrients (phosphorus, nitrogen) | — |
| Big Round Deep Hole South Lake | Polk | D | Nutrients (phosphorus, nitrogen) | — |
| Catfish Lake | Vilas | D | Cause unknown | — |
| Kettle Lake | Langlade | D | Mercury | — |
| Pokegama Lake | Barron | D | Nutrients (phosphorus, nitrogen) | — |
| Bittersweet Lake | Vilas | D | Nutrients (phosphorus, nitrogen) | — |
| Big Blake Lake | Polk | D | Nutrients (phosphorus, nitrogen) | — |
| Birch Lake | Sawyer | D | Nutrients (phosphorus, nitrogen) | — |
| Lake Chetac | Sawyer | D | Nutrients (phosphorus, nitrogen) | — |
| Park Lake | Columbia | D | Nutrients (phosphorus, nitrogen), Turbidity | ✓ |
| Lake of the Woods Barron Co. at | Barron | D | Nutrients (phosphorus, nitrogen) | — |
| Tainter Lake | Dunn | D | Nutrients (phosphorus, nitrogen) | ✓ |
| Long Trade Lake | Polk | D | Nutrients (phosphorus, nitrogen) | — |
| Mud Lake | Jefferson | D | Nutrients (phosphorus, nitrogen) | — |
| Mud Lake | Polk | D | Nutrients (phosphorus, nitrogen) | — |
| Petenwell Flowage Lake | Juneau | D | Dioxins, Mercury, Nutrients (phosphorus, nitrogen) +2 more | ✓ |
| Apple Lake | St. Croix | D | Nutrients (phosphorus, nitrogen) | ✓ |
| Peterson Lake | Oconto | D | Nutrients (phosphorus, nitrogen) | — |
| Hoerth Lake | Oconto | D | Nutrients (phosphorus, nitrogen) | — |
| Lake Dubay | Marathon | D | Nutrients (phosphorus, nitrogen) | ✓ |
| Spring Lake | Columbia | D | Nutrients (phosphorus, nitrogen) | — |
| Leota Lake | Rock | D | Nutrients (phosphorus, nitrogen) | — |
| Spirit Lake | Taylor | D | Nutrients (phosphorus, nitrogen) | — |
| White Ash Lake | Polk | D | Nutrients (phosphorus, nitrogen) | — |
| Weyers Lake | Manitowoc | D | Nutrients (phosphorus, nitrogen) | ✓ |
| Carstens Lake | Manitowoc | D | Nutrients (phosphorus, nitrogen) | ✓ |
| Lazy Lake | Columbia | D | Nutrients (phosphorus, nitrogen) | — |
| Pella Lake | Shawano | D | Cause unknown | — |
| Alabama Lake | Polk | D | Nutrients (phosphorus, nitrogen) | — |
| Eau Claire Lake | Eau Claire | D | Nutrients (phosphorus, nitrogen) | — |
| Lake Menomin | Dunn | D | Nutrients (phosphorus, nitrogen) | ✓ |
| East Bay Lake | Vilas | F | Cause unknown | — |
| Lake Redstone | Sauk | F | Nutrients (phosphorus, nitrogen) | ✓ |
| Cranberry Lake | Taylor | F | Nutrients (phosphorus, nitrogen) | — |
| Beaver Dam Lake | Dodge | F | Nutrients (phosphorus, nitrogen) | ✓ |
| Prairie Lake | Barron | F | Nutrients (phosphorus, nitrogen) | — |
| Indian Lake | Dane | F | Nutrients (phosphorus, nitrogen) | — |
| Big Eau Pleine Lake | Marathon | F | Nutrients (phosphorus, nitrogen) | ✓ |
| Long Lake | Manitowoc | F | Nutrients (phosphorus, nitrogen) | ✓ |
| Long Lake | Price | F | Nutrients (phosphorus, nitrogen) | — |
| Lake Winneconne | Winnebago | F | Cause unknown, Nutrients (phosphorus, nitrogen), Turbidity | ✓ |
| Lake Butte des Morts | Winnebago | F | Cause unknown, Nutrients (phosphorus, nitrogen), Turbidity | ✓ |
| Island Lake | Iron | F | Mercury | — |
| Mud Lake | Polk | F | Nutrients (phosphorus, nitrogen) | — |
| Mud Lake | Barron | F | Nutrients (phosphorus, nitrogen) | — |
| Altoona Lake | Eau Claire | F | Nutrients (phosphorus, nitrogen) | — |
| Eagle Lake | Racine | F | Nutrients (phosphorus, nitrogen) | — |
| Comus Lake | Walworth | F | Nutrients (phosphorus, nitrogen) | — |
| Fox Lake | Dodge | F | Nutrients (phosphorus, nitrogen), Turbidity | ✓ |
| Crowley Flowage Lake | Price | F | Mercury | — |
| Dynamite Lake | Langlade | F | Nutrients (phosphorus, nitrogen) | — |
| Lake Poygan | Winnebago | F | Cause unknown, Nutrients (phosphorus, nitrogen), Turbidity | ✓ |
| Lake Koshkonong | Jefferson | F | Nutrients (phosphorus, nitrogen), Turbidity | ✓ |
| Lower Park Falls Flowage Lake | Price | F | Mercury, Metals (other than mercury) | — |
| Ludden Lake | Iowa | F | Nutrients (phosphorus, nitrogen) | — |
| Tenmile Lake | Barron | F | Nutrients (phosphorus, nitrogen) | — |
| Beckers Lake | Calumet | F | Nutrients (phosphorus, nitrogen) | ✓ |
| Upper Kelly Lake | Waukesha | F | Nutrients (phosphorus, nitrogen) | — |
| Staples Lake | Barron | F | Nutrients (phosphorus, nitrogen) | — |
| West Bay Lake | Vilas | F | Cause unknown | — |
| Mason Lake | Adams | F | Nutrients (phosphorus, nitrogen) | ✓ |
| Lake Wisconsin Columbia Co. | Columbia | F | Mercury, Nutrients (phosphorus, nitrogen), PCBs | ✓ |
| Buffalo Lake | Marquette | F | PCBs | — |
| Tiedman Pond | Dane | F | Nutrients (phosphorus, nitrogen) | — |
| Klaus Lake | Oconto | F | Nutrients (phosphorus, nitrogen) | — |
| Clam River Flowage Lake | Burnett | F | Nutrients (phosphorus, nitrogen) | — |
| Pixley Flowage Lake | Price | F | Mercury | — |
| Upper Vermillion Lake | Barron | F | Nutrients (phosphorus, nitrogen) | — |
| Chequamegon Waters Flowage Lake | Taylor | F | Nutrients (phosphorus, nitrogen) | — |
| Odana Pond | Dane | F | Nutrients (phosphorus, nitrogen), Salinity / chlorides | — |
| Little Green Lake | Green Lake | F | Nutrients (phosphorus, nitrogen) | ✓ |
| Lotus Lake | Polk | F | Nutrients (phosphorus, nitrogen) | — |
| Prairie Lake | Barron | F | Nutrients (phosphorus, nitrogen) | — |
| Yellowstone Lake | Lafayette | F | Nutrients (phosphorus, nitrogen) | — |
| Mead Lake | Clark | F | Nutrients (phosphorus, nitrogen), Turbidity | ✓ |
| Lake Delton | Sauk | F | Nutrients (phosphorus, nitrogen) | ✓ |
| Lake Shangri-la | Kenosha | F | Nutrients (phosphorus, nitrogen) | — |
| Lake Wisconsin Palisade Street Bay | Sauk | F | Mercury, Nutrients (phosphorus, nitrogen), PCBs | ✓ |
| North Bay Lake | Vilas | F | Cause unknown | — |
| Neshonoc Lake | La Crosse | F | Mercury, Nutrients (phosphorus, nitrogen), Turbidity | — |
| Prairie Lake | Barron | F | Nutrients (phosphorus, nitrogen) | — |
| Little Twin Lake | Green Lake | F | Nutrients (phosphorus, nitrogen) | — |
| Pepin Lake | Pepin | F | Nutrients (phosphorus, nitrogen) | — |
| St. Louis River Outlet Upstream of John A. Blatnik Memorial Bridge Lake | Douglas | F | Mercury, Metals (other than mercury), PCBs | — |
| Upper Clam Lake | Burnett | F | Nutrients (phosphorus, nitrogen) | — |
| Carrol Lake | Oneida | F | Nutrients (phosphorus, nitrogen) | — |
| Mead Lake Nb Test Site | Clark | F | Nutrients (phosphorus, nitrogen), Turbidity | ✓ |
| Mead Lake Nb Control Site | Clark | F | Nutrients (phosphorus, nitrogen), Turbidity | ✓ |
| Dexter Lake | Wood | F | Nutrients (phosphorus, nitrogen), Pathogens (E. coli, fecal) | — |
| Lake Tomah | Monroe | F | Nutrients (phosphorus, nitrogen) | — |
| Mb-2a Cul Lake | Sawyer | F | Mercury | — |
| Little Yellow Lake | Burnett | F | Nutrients (phosphorus, nitrogen) | — |
| Silver Creek Estuary Lake | Green Lake | F | Pathogens (E. coli, fecal) | — |
| Graber Pond | Dane | F | Nutrients (phosphorus, nitrogen) | — |
| Lower Kelly Lake | Waukesha | F | Nutrients (phosphorus, nitrogen) | — |
Frequently Asked Questions
How many lakes are impaired in Wisconsin?
519 of 1,449 graded Wisconsin lakes (36%) are listed as impaired in the most recent EPA ATTAINS reporting cycle. Of those, 466 are on the federal Clean Water Act §303(d) list and 75 have an approved Total Maximum Daily Load (TMDL) restoration plan.
What does Clean Water Act §303(d) mean?
Section 303(d) of the federal Clean Water Act requires every state to identify waters that don't meet water quality standards even after pollution control measures. Each listed water must then have a Total Maximum Daily Load (TMDL) developed — a plan that caps how much of each pollutant can enter the waterbody. The "303(d) list" is the impaired-waters list. The EPA reviews each state's list every two years.
What are the top causes of impairment in Wisconsin?
The most common causes flagged across Wisconsin's impaired lakes are: Nutrients (phosphorus, nitrogen) (297 lakes); Mercury (135 lakes); Cause unknown (89 lakes); PCBs (26 lakes); Metals (other than mercury) (16 lakes); Turbidity (15 lakes). Mercury is widespread in fish tissue across the upper Midwest from atmospheric deposition. Nutrient impairment (phosphorus, nitrogen) typically reflects agricultural runoff and urban stormwater.
Can I swim in an impaired lake?
It depends on the cause of impairment. A lake impaired for "mercury in fish tissue" is generally safe to swim in — the warning is about long-term consumption of fish. A lake impaired for "pathogens" (E. coli) or "algal growth" may pose a swimming risk and often has a separate beach advisory. Check the cause categories listed for each lake below, and consult your state health department's beach monitoring program for current advisories.
Where does this impairment data come from?
Every impairment record on this page comes from the EPA's ATTAINS (Assessment and TMDL Tracking and Implementation System) public dataset, the federal repository of state-reported water quality assessments. EPA ATTAINS is published as GeoParquet files on the EPA Office of Water S3 bucket and refreshed several times per year. Causes and use-support codes follow EPA's standard taxonomy.
Data source
Impairment data from the EPA ATTAINS (Assessment and TMDL Tracking and Implementation System) public dataset. Assessment unit IDs are matched to LakeGrade waterbodies by name and proximity; some lakes may not appear here if their ATTAINS name doesn't match our naming convention. For an official query, consult Wisconsin's state water-quality agency.