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LakeQuality

Reservoirs in Wisconsin

60 of 185 graded Wisconsin lakes (32%) are man-made reservoirs in the USACE National Inventory of Dams. 36 carry a High or Significant hazard rating.

Why these Wisconsin reservoirs were built

47
Recreation
5
Other
4
Navigation
3
Water Supply
1
Fire Protection, Stock, Or Small Fish Pond
60
Total reservoirs
20,471
Total surface acres
348,964
Normal storage (ac-ft)
36
High or Significant hazard

All 60 Wisconsin reservoirs (by surface area)

ReservoirCountyGradeSurface areaYear builtPurposeHazard
Otisco LakeOnondagaD2,291 ac1956RecreationHigh
Lake PlacidEssexA2,173 ac1904RecreationLow
Hemlock LakeLivingstonB2,054 ac1926Water SupplyHigh
Peck LakeFultonB1,300 ac1910OtherSignificant
Lake BonaparteLewisA1,286 ac1933OtherLow
Silver LakeWyomingC761 ac1982RecreationSignificant
Canadice LakeOntarioA657 ac1947Water SupplyHigh
Galway LakeSaratogaB564 ac1982RecreationHigh
Deruyter ReservoirMadisonA560 ac1863NavigationHigh
South LakeHerkimerA499 ac1901RecreationHigh
Lincoln PondEssexA475 ac1911RecreationHigh
Cuba LakeAlleganyB465 ac1872RecreationHigh
Friends LakeWarrenB450 ac1954RecreationLow
Friends LakeWarrenA450 ac1954RecreationLow
Deer River Flow LakeFranklinF403 ac1904RecreationLow
Burden LakeRensselaerA369 ac1916RecreationSignificant
Tuscarora LakeMadisonA362 ac1850NavigationHigh
Kinderhook LakeColumbiaD350 ac1886OtherLow
Findley LakeChautauquaC330 ac1820RecreationLow
Brantingham LakeLewisB327 ac1914RecreationLow
Sleepy Hollow LakeGreeneD324 ac1972RecreationHigh
Lake MoraineMadisonA260 ac1836NavigationHigh
Jamesville ReservoirOnondagaD252 ac1874NavigationHigh
Pleasant LakeFultonB248 ac1926OtherLow
Lake CarmelPutnamD240 ac1930RecreationHigh
Pleasure LakeSullivanD218 ac1875RecreationHigh
Hadlock PondWashingtonB194 ac1896RecreationHigh
Lime LakeCattaraugusC154 ac1850RecreationSignificant
Upper Little York LakeCortlandB150 ac2015RecreationSignificant
Bradley Brook ReservoirMadisonA141 ac1878OtherSignificant
Otter LakeOneidaD135 ac1880RecreationLow
Oquaga LakeBroomeA134 ac—RecreationLow
Hatch LakeMadisonB134 ac1836RecreationLow
Canada LakeFultonB128 ac1923RecreationSignificant
Robinson PondColumbiaB125 ac1915RecreationSignificant
Kirk LakePutnamD124 ac1871RecreationSignificant
Duane LakeSchenectadyD120 ac1926RecreationLow
Roaring Brook LakePutnamC112 ac1959RecreationHigh
Genegantslet LakeChenangoB112 ac1900RecreationHigh
Lake LuzerneWarrenA111 ac1860RecreationSignificant
Sagamore LakePutnamD96 ac1946RecreationSignificant
Plymouth ReservoirChenangoD77 ac1827RecreationSignificant
Guilford LakeChenangoB74 ac1827Water SupplyHigh
Barrett PondPutnamB70 ac1920RecreationLow
Swamp PondSullivanD64 ac1920RecreationLow
Sage PondOswegoD60 ac1957RecreationSignificant
Kasoag LakeOswegoC58 ac1820RecreationLow
Seven Hills LakePutnamD56 ac1957RecreationLow
Lake PeekskillPutnamD52 ac1928RecreationHigh
China PondPutnamA45 ac1927RecreationLow
Ellis LakeCortlandC43.6 ac1902RecreationHigh
Lake TibetPutnamD40 ac1950Fire Protection, Stock, Or Small Fish PondLow
Beaver LakeBroomeD40 ac1939RecreationLow
Deer LakeBroomeD32 ac—RecreationLow
Lake ForestWarrenC28 ac1973RecreationLow
Howlands LakeWestchesterF26 ac1895RecreationSignificant
Lake LincolndaleWestchesterF22 ac1935RecreationHigh
Truitt PondChenangoF19 ac1947RecreationLow
Lake LucilleRocklandF17 ac1935RecreationHigh
Anawanda LakeSullivanA9 ac1952RecreationLow

Frequently Asked Questions

How many reservoirs are in Wisconsin?

60 of 185 graded Wisconsin lakes (32%) are man-made reservoirs in the USACE National Inventory of Dams. 36 are rated High or Significant hazard, meaning failure would put downstream lives or property at substantial risk. The oldest matched dam dates to 1820.

What's the largest reservoir in Wisconsin?

The largest matched reservoir in Wisconsin is Otisco Lake in Onondaga County at 2,291 acres of normal surface area, impounded by the Otisco Lake Dam (completed 1956).

What's the difference between a reservoir and a natural lake?

A reservoir is a body of water impounded by a man-made dam — typically built for flood control, hydroelectric power, water supply, irrigation, or recreation. A natural lake formed without human intervention, usually from glacial scouring, volcanic activity, or river meandering. Reservoirs typically have shoreline that fluctuates with seasonal water level management, while natural lakes have more stable shorelines. The USACE National Inventory of Dams classifies every regulated dam in the United States, which is how we identify which LakeGrade lakes are actually reservoirs.

What does the hazard class mean?

USACE assigns each dam a hazard potential classification based on what would happen downstream if the dam failed — NOT how likely the dam is to fail. "Low" hazard means dam failure would cause no probable loss of life and only low economic loss. "Significant" means probable loss of life is unlikely but appreciable economic damage would occur. "High" means probable loss of life and significant economic damage. The classification is about consequence, not condition. Many High-hazard dams are perfectly safe; they're rated High because populated areas have grown downstream over time.

Where does this reservoir data come from?

Every reservoir record on this page is matched to the USACE National Inventory of Dams (NID), the federal database of all dams ≥25 ft tall or impounding ≥50 acre-feet, plus any dam that poses a Significant or High hazard regardless of size. The NID is published by the U.S. Army Corps of Engineers and updated annually. Surface area, storage capacity, dam height, and hazard classification come directly from NID records.

Data source

Reservoir data from the USACE National Inventory of Dams (NID), the federal database of all regulated dams. Dam attributes (height, year completed, storage capacity, hazard class) are matched to LakeGrade lakes by proximity and dam-name similarity. Some lakes may be reservoirs that aren't matched if the dam record uses a name substantially different from our lake name.