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

Reservoirs in Oregon

37 of 659 graded Oregon lakes (6%) are man-made reservoirs in the USACE National Inventory of Dams. 33 carry a High or Significant hazard rating.

Reading the Oregon reservoir landscape

37 reservoirs in Oregon appear in the USACE National Inventory of Dams. That's a meaningful share — reservoir lakes carry their own ecology and access patterns distinct from natural lakes, including managed water levels, drawdowns timed to the dam's purpose, and shoreline mix dominated by structures built post-impoundment.

The leading reservoir purpose in Oregon is flood control. Flood-control reservoirs typically hold water at a low pool except during high-water events, when the dam captures and slowly releases excess inflow downstream. That operating pattern means shallow shoreline access, exposed mudflats during low-pool seasons, and water-level fluctuations that limit fixed-dock development. The fishing and recreation use tends to concentrate in the deeper main-channel areas year-round.

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 Oregon reservoirs were built

Flood Risk Reduction

Irrigation

Hydroelectric

Recreation

Fish and Wildlife Pond

Other

Water Supply

Total reservoirs

157,855

Total surface acres

4,143,364

Normal storage (ac-ft)

High or Significant hazard

All 37 Oregon reservoirs (by surface area)

Reservoir	County	Grade	Surface area	Year built	Purpose	Hazard
Fremont Bridge Lake	Klamath	D	85,000 ac	1921	Hydroelectric	High
Wickiup Reservoir	Deschutes	C	11,330 ac	1949	Fish and Wildlife Pond	High
Crane Prairie Reservoir	Deschutes	D	4,940 ac	1940	Irrigation	High
Crane Prairie Reservoir	Deschutes	D	4,940 ac	1940	Irrigation	High
Crescent Lake	Klamath	A	4,008 ac	1956	Irrigation	High
Round Butte Dam Forebay Lake	Jefferson	D	4,000 ac	1964	Hydroelectric	High
Billy Chinook Reservoir	Jefferson	C	4,000 ac	1964	Hydroelectric	High
Green Peter Lake	Linn	A	3,720 ac	1967	Flood Risk Reduction	High
Siltcoos Lake	Lane	D	3,585 ac	1964	Other	Low
Detroit Lake	Marion	B	3,490 ac	1953	Flood Risk Reduction	High
Lost Creek Lake	Jackson	C	3,430 ac	1976	Flood Risk Reduction	High
Prineville Reservoir	Crook	D	3,028 ac	1961	Flood Risk Reduction	High
Phillips Lake	Baker	NR	2,235 ac	1968	Flood Risk Reduction	High
Howard Prairie Lake	Jackson	D	1,990 ac	1958	Hydroelectric	High
Cold Springs Reservoir	Umatilla	F	1,550 ac	1908	Irrigation	High
Wallowa Lake	Wallowa	A	1,530 ac	1931	Irrigation	High
Timothy Lake	Clackamas	A	1,430 ac	1956	Hydroelectric	High
Cougar Lake	Lane	A	1,280 ac	1963	Flood Risk Reduction	High
Foster Lake	Linn	C	1,220 ac	1967	Flood Risk Reduction	High
Mckay Lake	Umatilla	NR	1,200 ac	1927	Flood Risk Reduction	High
Henry Hagg Lake	Washington	A	1,157 ac	1975	Irrigation	High
Applegate Lake	Jackson	A	1,041 ac	1980	Flood Risk Reduction	High
Bully Creek Lake	Malheur	D	985 ac	1963	Flood Risk Reduction	High
Blue River Lake	Lane	B	975 ac	1968	Flood Risk Reduction	High
Fourmile Lake	Klamath	A	962 ac	1922	Flood Risk Reduction	Low
Unity Reservoir	Baker	D	960 ac	1938	Irrigation	High
Thief Valley Reservoir	Union	F	807 ac	1932	Irrigation	High
Emigrant Lake	Jackson	C	806 ac	1960	Flood Risk Reduction	Low
Galesville Reservoir	Douglas	A	640 ac	1985	Irrigation	High
Lemolo Lake	Douglas	D	419.1 ac	1955	Hydroelectric	High
Fish Lake	Jackson	D	415 ac	1908	Flood Risk Reduction	High
Willow Creek Reservoir	Morrow	NR	269 ac	1982	Flood Risk Reduction	High
Pine Hollow Reservoir	Wasco	D	235 ac	1969	Irrigation	High
Hawks Lake	Klamath	NR	227 ac	1973	Recreation	Low
Horse Heaven Reservoir Along East Shore	Crook	NR	28.1 ac	1953	Irrigation	Significant
Haskins Reservoir	Yamhill	NR	23 ac	1930	Water Supply	Significant
Devil'S Lake	Lincoln	D	—	—	Recreation	High

Frequently Asked Questions

How many reservoirs are in Oregon?

37 of 659 graded Oregon lakes (6%) are man-made reservoirs in the USACE National Inventory of Dams. 33 are rated High or Significant hazard, meaning failure would put downstream lives or property at substantial risk. The oldest matched dam dates to 1908.

What's the largest reservoir in Oregon?

The largest matched reservoir in Oregon is Fremont Bridge Lake in Klamath County at 85,000 acres of normal surface area, impounded by the Link River Diversion Dam (completed 1921).

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 Oregon reservoirs

Compare cabins, lodges, and vacation rentals near the largest reservoirs in Oregon — 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.