A red sun low over Slim Lake through wildfire haze, its reflection a column of orange on the water

Reservoirs in Iowa

116 of 330 graded Iowa lakes (35%) are man-made reservoirs in the USACE National Inventory of Dams. 84 carry a High or Significant hazard rating.

Reading the Iowa reservoir landscape

Iowa hosts 116 man-made reservoirs in the USACE National Inventory of Dams — a dense reservoir landscape that reflects significant federal, state, and utility-led impoundment construction over the 20th century. Reservoir lakes behave differently than natural lakes: water levels are managed for the dam's primary purpose, residence time depends on inflow and release schedules, and depth profiles follow the original river-valley topography rather than the bowl shape of glacial lakes.

Recreation is the headline purpose for the largest share of Iowa's reservoirs — lakes where the dam exists explicitly to create surface water for fishing, boating, and adjacent shoreline development. Pool levels are typically maintained more stably than at flood-control or hydro reservoirs, which supports fixed-dock access, consistent boat ramps, and the kind of shoreline economy that natural-lake counterparts in the state share.

The USACE National Inventory of Dams (NID) catalogs every dam in the United States above a size threshold — typically 25 feet in height or 50 acre-feet in maximum storage, plus all dams classified as high-hazard regardless of size. The reservoir records below pull NID fields (year built, hazard class, maximum storage, surface area at normal pool, dam length, primary purpose) and pair them with water-quality data where the impoundment also appears in EPA's lake-monitoring inventory.

Why these Iowa reservoirs were built

Recreation

Water Supply

Flood Risk Reduction

Fire Protection, Stock, Or Small Fish Pond

Other

Fish and Wildlife Pond

Debris Control

116

Total reservoirs

27,951

Total surface acres

412,645

Normal storage (ac-ft)

High or Significant hazard

All 116 Iowa reservoirs (by surface area)

Reservoir	County	Grade	Surface area	Year built	Purpose	Hazard
Rathbun Lake	Appanoose	C	11,013 ac	1969	Flood Risk Reduction	High
Lake Macbride	Johnson	D	950 ac	1930	Recreation	Significant
Big Creek Lake	Polk	F	885 ac	1970	Flood Risk Reduction	High
Three Mile Lake	Union	D	880 ac	1995	Flood Risk Reduction	Significant
Little River Lake	Decatur	F	787 ac	1984	Flood Risk Reduction	High
Lake Icaria	Adams	F	700 ac	1974	Flood Risk Reduction	Significant
Brushy Creek Lake	Webster	F	690 ac	1998	Recreation	High
Lake of the Hills	Scott	C	657 ac	1972	Other	High
Rock Creek Max Depth Lake	Jasper	F	640 ac	—	Recreation	Significant
Rock Creek Beach Lake	Jasper	NR	640 ac	—	Recreation	Significant
Twelve Mile Lake	Union	F	633 ac	1983	Flood Risk Reduction	High
Lake Sugema	Van Buren	F	574 ac	1992	Recreation	High
Pleasant Creek Lake	Linn	D	410 ac	1977	Flood Risk Reduction	High
Lost Grove Lake	Scott	C	350 ac	2012	Recreation	High
Green Valley Lake	Union	F	336 ac	1953	Recreation	Significant
West Lake Osceola	Clarke	D	306 ac	1935	Water Supply	Significant
Lake Darling Max Depth	Washington	F	304 ac	1950	Recreation	Significant
Roberts Creek Lake	Marion	F	296 ac	1968	Recreation	Significant
Center Lake	Dickinson	F	287 ac	2009	Recreation	Low
Badger Creek Max Depth Lake	Madison	F	276 ac	1980	Recreation	Significant
Lake Belva Deer	Keokuk	F	247 ac	2001	Recreation	Significant
Dale Maffitt Reservoir	Dallas	A	230 ac	1944	Water Supply	High
Easter Lake	Polk	D	218 ac	1967	Recreation	Significant
Summit Lake	Union	F	202 ac	1935	Recreation	Low
Prairie Rose Lake	Shelby	F	200 ac	1960	Recreation	Significant
Lake Geode	Des Moines	F	195 ac	1949	Recreation	Significant
Big Hollow Lake	Des Moines	F	178 ac	2008	Recreation	Significant
Lake Anita	Cass	F	171 ac	1970	Recreation	Significant
Hawthorn Lake	Mahaska	D	160 ac	1979	Recreation	Significant
Don Williams Lake	Boone	F	160 ac	1965	Recreation	Significant
Morris Lake	Lucas	F	155 ac	1993	Water Supply	Significant
Viking Lake	Montgomery	F	148 ac	1957	Recreation	Significant
Lake Miami Max Depth	Monroe	F	140 ac	1966	Recreation	Significant
Volga Lake	Fayette	F	135 ac	1980	Recreation	Significant
Swan Lake Max Depth	Carroll	F	130 ac	1935	Fish and Wildlife Pond	Low
Lake of Three Fires Max Depth	Taylor	F	125 ac	1967	Recreation	Significant
Union Grove Lake	Tama	F	117 ac	1920	Recreation	Significant
Cedar Lake	Linn	F	115 ac	—	Flood Risk Reduction	Low
Arrowhead Lake	Sac	B	110 ac	—	Other	Low
Upper Pine Lake	Hardin	F	110 ac	1934	Recreation	Significant
Hickory Grove Lake	Story	D	107 ac	1966	Recreation	Significant
Bob White Lake	Wayne	B	104 ac	1900	Recreation	Significant
Diamond Lake	Poweshiek	F	93 ac	1952	Water Supply	Significant
Red Haw Lake	Lucas	F	93 ac	1934	Recreation	High
Lake Iowa	Iowa	F	92 ac	1962	Recreation	Significant
Iowa Lkt Lake	Iowa	NR	92 ac	1962	Recreation	Significant
Lake Fisher	Davis	F	87 ac	1937	Water Supply	Significant
Lower Pine Lake	Hardin	F	85 ac	1922	Recreation	Significant
Pine Lake South Beach	Hardin	NR	85 ac	1922	Recreation	Significant
Lpinelk T Lake	Hardin	NR	85 ac	1922	Recreation	Significant
Cedar Lake	Madison	F	84 ac	1939	Water Supply	Significant
Ellis Lake	Lucas	F	80 ac	1993	Water Supply	Significant
Binder Lake	Adams	D	79.4 ac	1942	Water Supply	Significant
Loch Ayr Lake	Ringgold	D	78 ac	1930	Water Supply	Significant
Lake Pahoja	Lyon	F	71.5 ac	1974	Fire Protection, Stock, Or Small Fish Pond	Significant
Briggs Woods Lake	Hamilton	F	70 ac	1968	Recreation	Significant
Sands Timber Lake	Taylor	F	70 ac	1993	Flood Risk Reduction	Significant
Littlefield Lake	Audubon	F	69 ac	1977	Flood Risk Reduction	High
Corydon Reservoir	Wayne	F	66.9 ac	1974	Recreation	Significant
Crawford Creek Lake	Ida	F	63 ac	1976	Recreation	Significant
Otter Creek Lake	Tama	D	60 ac	1968	Recreation	Significant
Smith Lake	Kossuth	F	53 ac	1965	Recreation	Significant
Badger Lake	Webster	F	50 ac	1963	Recreation	Significant
Lake Hendricks	Howard	F	50 ac	1960	Recreation	Significant
Greenfield Lake	Adair	F	49.6 ac	1979	Water Supply	High
Hooper Pond Lake	Warren	D	44.8 ac	1996	Recreation	Significant
Meadow Lake	Adair	F	42 ac	1964	Recreation	Significant
Fogle Lake	Ringgold	F	41.5 ac	1996	Recreation	Significant
Mill Creek Lake	O'Brien	D	40 ac	1934	Recreation	Low
Casey Lake	Tama	F	39.2 ac	1970	Recreation	Low
Hannen Lake	Benton	F	39 ac	1959	Recreation	Significant
Silver Lake Max Depth	Delaware	F	39 ac	1948	Recreation	Low
Yellow Smoke Lake	Crawford	D	38.4 ac	1980	Recreation	High
Mckinley Lake	Union	F	38 ac	1920	Recreation	Significant
Pierce Creek Lake	Page	F	38 ac	1969	Fire Protection, Stock, Or Small Fish Pond	Significant
Lake Meyer	Winneshiek	D	37.6 ac	1966	Recreation	Significant
Humeston Reservoir	Wayne	F	37.4 ac	1916	Water Supply	Significant
Beaver Lake	Dallas	F	34 ac	1990	Recreation	Significant
Mormon Trail Lake	Adair	B	33 ac	1965	Recreation	Low
Dog Creek Lake	O'Brien	D	29.3 ac	1967	Other	Significant
Railroad Lake	Scott	C	29 ac	1983	Recreation	Significant
Kent Park Lake	Johnson	B	28.7 ac	1972	Recreation	Low
Nodaway Lake	Adair	D	27 ac	1936	Water Supply	Significant
Central Park Lake	Jones	D	25 ac	1965	Recreation	Low
Williamson Pond Max Depth	Lucas	F	25 ac	1915	Recreation	Low
Central Park Lake	Jones	NR	25 ac	1965	Recreation	Low
Windmill Lake	Taylor	F	24.5 ac	1969	Recreation	Low
Lake Orient	Adair	F	23.4 ac	1969	Water Supply	Significant
Rodgers Lake	Benton	F	23 ac	1977	Recreation	Significant
Eldred Sherwood Lake	Hancock	F	23 ac	1967	Other	Low
Lacey Keosauqua Lake	Van Buren	A	23 ac	1930	Recreation	Low
White Oak Lake	Mahaska	F	20 ac	1983	Recreation	Significant
Willow Lake	Harrison	B	19 ac	1976	Debris Control	Low
Mariposa Lake	Jasper	B	18.7 ac	1952	Recreation	Low
Slipbluff Lake	Decatur	A	18 ac	1970	Recreation	Low
Green Castle Lake	Marshall	C	17 ac	1954	Recreation	Significant
Wilson Lake	Taylor	F	16.5 ac	1967	Recreation	Low
Oldham Lake	Monona	C	16.1 ac	1963	Fire Protection, Stock, Or Small Fish Pond	Low
Fin And Feather Lake	Cerro Gordo	F	16 ac	1972	Recreation	Low
Arrowhead Lake	Pottawattamie	F	15.7 ac	1959	Fire Protection, Stock, Or Small Fish Pond	Low
Cold Springs Lake	Cass	D	15.5 ac	1949	Recreation	Low
Poll Miller Park Lake	Lee	B	15.2 ac	1971	Recreation	Low
Spring Lake	Cherokee	D	15 ac	—	Recreation	Low
Thayer Lake	Union	F	14.1 ac	1930	Recreation	Low
Blue Grass Lake	Scott	C	13.8 ac	1974	Recreation	Significant
East Lake Osceola	Clarke	F	13 ac	1915	Water Supply	Significant
Springbrook Lake	Guthrie	D	12 ac	1934	Recreation	Significant
Fort des Moines Park Pond	Polk	F	11.6 ac	1977	Recreation	High
Nelson Lake	Crawford	F	11 ac	1964	Recreation	Low
Moorehead Lake	Ida	D	10.9 ac	1966	Fire Protection, Stock, Or Small Fish Pond	Low
Crystal Lake Max Depth	Hancock	F	9.7 ac	2003	—	Low
Gustafson Lake	Buena Vista	D	9.7 ac	1974	Recreation	Significant
Lambach Lake	Scott	C	9 ac	1972	Recreation	Low
Manteno Lake	Shelby	D	4.4 ac	1964	Fire Protection, Stock, Or Small Fish Pond	Low
Thomas Mitchell Lake	Polk	C	4.2 ac	1971	Recreation	Significant
South Prairie Lake	Black Hawk	F	—	1994	Flood Risk Reduction	High

Frequently Asked Questions

How many reservoirs are in Iowa?

116 of 330 graded Iowa lakes (35%) are man-made reservoirs in the USACE National Inventory of Dams. 84 are rated High or Significant hazard, meaning failure would put downstream lives or property at substantial risk. The oldest matched dam dates to 1900.

What's the largest reservoir in Iowa?

The largest matched reservoir in Iowa is Rathbun Lake in Appanoose County at 11,013 acres of normal surface area, impounded by the Rathbun Dam (completed 1969).

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 LakeQuality 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.

Where to stay near Iowa reservoirs

Compare cabins, lodges, and vacation rentals near the largest reservoirs in Iowa — live availability and prices for boating, fishing, and lake trips.

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More on reservoirs and water quality

Are Reservoirs Cleaner Than Natural Lakes?

Dam-built reservoirs and natural lakes graded side by side on the same nutrient and algae measurements — the gap, the reasons behind it, and the exceptions.

Do Deeper Lakes Have Better Water Quality?

Surveyed maximum depth against A–F nutrient-and-algae grades: the pattern, the shallow lakes that still grade an A, and why land use beats bathymetry.

Lake Water Quality Grades Explained: What A–F Means

How lakes are graded A–F on nutrients and algae using EPA ecoregion condition classes, what each letter means in the water, and why an A is not a clearance.

Why Lakes Turn Green: Phosphorus and Nutrient Pollution

How phosphorus and nutrient runoff drive algae growth and turn lakes green, where the nutrients come from, and what it means for a lake's grade.

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 LakeQuality 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.