Largest lakes & reservoirs in Washington by water volume
The estimated volume of water that a lake contains is measured at the lake’s normal elevation. By this measure, the world’s largest freshwater lake is Siberia’s Lake Baikal.Water Volume can be measured in acre-feet, in cubic miles, or in cubic kilometers. One acre-foot is the amount of water needed to cover one acre (43,560 square feet) to a depth of one foot. One cubic mile equals 3,379,200 acre-feet. One cubic kilometer equals 810,713 acre-feet. 1 acre-foot is equal to 325,851 US gallons. Siberia’s Lake Baikal contains about 6,276,367,740,000,000 gallons of freshwater – nearly 1 million gallons for every living person on earth.
The other – and more widely used – measure of a lake’s size is the lake’s surface acreage. By that measure, the world’s largest freshwater lake is North America’s Lake Superior.
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.
You can find many of the the world’s largest lakes (by water volume) on LakeLubbers. Note: For some lakes, the water volume data is unknown or does not apply, so you may see fewer lakes than the total 58 articles we have published for Washington lakes.
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Below are lakes within USA > US West Region > Washington > Compared by water volume. This list does not represent all lakes in Washington, only the 58 Washington lake articles we have published on the LakeLubbers website.
Lake name  |
Water vol. in ac-ft |
Lake description |
|---|---|---|
| Lake Roosevelt, WA (Northeast Washington, US West Region, USA, Washington) |
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 Region, WA, US West Region, USA, Washington) |
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 Region, WA, US West Region, USA, Washington) |
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, OR/WA (Eastern Oregon, Oregon, South Central Washington, US West Region, USA, Washington) |
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, WA (North Central Washington, US West Region, USA, Washington) |
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, WA (North Central Washington, US West Region, USA, Washington) |
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, WA (Olympic Peninsula & Pacific Coast Region, WA, US West Region, USA, Washington) |
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, Canada, North Central Washington, US West Region, USA, Washington) |
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, WA (Northwest Washington & Islands, WA, US West Region, USA, Washington) |
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, WA (North Central Washington, US West Region, USA, Washington) |
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, WA (Olympic Peninsula & Pacific Coast Region, WA, US West Region, USA, Washington) |
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, WA (North Central Washington, US West Region, USA, Washington) |
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… |
