Largest lakes & reservoirs in Washington by water volume
This is a comparison for lakes within USA > West > Washington > - Compared by Largest Lakes - Water Volume in acre-foot.For some lakes, "Largest Lakes - Water Volume" is unknown or does not apply, so this table may display fewer lakes than the total 58 articles we have published for Washington lakes.
Note: In the United States, an acre foot is a unit of volume used to refer to large-scale bodies of water. It is defined by the volume of water needed to cover 1 acre of surface area to a depth of 1 foot.
Search results: Sort lakes by water volume
Lake name ![]() |
Water vol. in ac-ft ![]() |
Lake description |
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Lake Roosevelt (Northeast Washington, USA, Washington, West) |
9,402,000 ac-ft | (Also known as Lake Franklin D. Roosevelt) Lake Roosevelt, located approximately 90 miles northwest of Spokane, Washington, covers 82,000 acres with a shoreline of 630 miles. Lake Roosevelt, al… |
Lake Washington WA (Seattle & Puget Sound, USA, Washington, West) |
2,350,000 ac-ft | Lake Washington has the distinction of being the second largest natural lake in the state of Washington. This glacial lake is long and narrow, a “ribb… |
Riffe Lake (Seattle & Puget Sound, USA, Washington, West) |
1,686,000 ac-ft | (Also known as Riffe Reservoir, Mossyrock Lake, Davisson Lake) Riffe Lake by any other name would still be a fantastic recreational spot. The name confusion for this man-made reservoir in the Seattle and Puget Sou… |
Lake Wallula (Eastern, Oregon, South Central Washington, USA, Washington, West) |
1,350,000 ac-ft | Lake Wallula, a 64 mile long reservoir, is a wide open glassy lake that extends from northeastern Oregon to southeastern Washington. Lake Wallula rece… |
Banks Lake (North Central Washington, USA, Washington, West) |
1,275,000 ac-ft | Banks Lake is a 27 mile equalizing reservoir and part of the Columbia Basin Project, a major water resource project to provide irrigation water to fer… |
Lake Chelan (North Central Washington, USA, Washington, West) |
1,040,000 ac-ft | From the Salish Indian word for “deep notch”, Lake Chelan is the third deepest lake in the United States with a maximum depth of almost 1500 feet. Lak… |
Lake Ozette (Olympic Peninsula & Pacific Coast, USA, Washington, West) |
1,012,310 ac-ft | (Also known as Ozette Lake) Nestled in dense forest just a few miles from the Pacific Coast, Lake Ozette sits snuggled into Washington’s Olympic Peninsula tourism region, on the… |
Ross Lake (British Columbia, Canada, North Central Washington, USA, Washington, West) |
770,000 ac-ft | (Also known as Ross Reservoir) Spectacular Ross Lake is one of the seldom seen gems in north-central Washington. This fantastic 22-mile long reservoir covers 11,680 acres along the… |
Whatcom Lake (Northwest Washington & Islands, USA, Washington, West) |
767,700 ac-ft | (Also known as Lake Whatcom) Whatcom Lake is a 5,000-acre natural lake surrounded by mountainous terrain located in Whatcom County, Washington. Whatcom is from a Nooksack Indian w… |
Potholes Reservoir (North Central Washington, USA, Washington, West) |
500,000 ac-ft | Potholes Reservoir was formed by the building of the O’Sullivan Dam which is one of the largest earthfill dams in the United States. The name “pothole… |
Lake Cushman (Olympic Peninsula & Pacific Coast, USA, Washington, West) |
450,000 ac-ft | Nestled in the foothills of the majestic Olympic Mountains, Lake Cushman is known for its clear, blue water and alpine beauty. With 23 miles of shorel… |
Cle Elum Lake (North Central Washington, USA, Washington, West) |
436,900 ac-ft | (Also known as Lake Cle Elum) Providing much needed water to the dry, fertile soil of north-central Washington, Cle Elum Lake is the largest of four irrigation storage reservoirs i… |