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 Sacajawea, WA (South Central Washington, US West Region, USA, Washington) |
406,500 ac-ft | Named after the Shoshone woman, Sacajawea, who was a member of the Lewis and Clark expedition, Lake Sacajawea is located in south-central Washington. … |
| Lake Entiat, WA (North Central Washington, US West Region, USA, Washington) |
382,000 ac-ft | (Also known as Rocky Reach Reservoir) No trip to the north central part of Washington would be complete without a visit to Lake Entiat and the Rocky Reach Dam. Lake Entiat is a 9,100 acre … |
| Lake Wenatchee, WA (North Central Washington, US West Region, USA, Washington) |
364,560 ac-ft | Lake Wenatchee is a high mountain lake located in the Wenatchee National Forest in the Cascade Mountains of Washington state. Fed by the Little Wenatc … |
| Lake Sammamish, WA (Seattle & Puget Sound Region, WA, US West Region, USA, Washington) |
283,860 ac-ft | At just under 5,000 acres, Lake Sammamish is one of the major recreational lakes in the state. The lake provides activities for fishermen, boaters, je … |
| Lake Celilo, OR/WA (Mt. Hood-The Gorge Region, OR, Oregon, Southwest Washington, US West Region, USA, Washington) |
277,000 ac-ft | (Also known as Dalles Lock and Dam) Beautiful and serene Lake Celilo is located off of I-84 about an hour and a half east of Portland, Oregon. Lake Celilo stretches 24 miles long and str … |
| Lake Osoyoos, WA / Canada (British Columbia, Canada, Canada, North Central Washington, US West Region, USA, Washington) |
266,800 ac-ft | (Also known as Osoyoos Lake) Lake Osoyoos spans more than 5,700 acres and straddles the border of British Columbia, Canada and Washington state in the United States. The Okanagan … |
| Lake Spokane, WA (Northeast Washington, US West Region, USA, Washington) |
243,341 ac-ft | (Also known as Long Lake) Lake Spokane, a 24 mile long reservoir, is so named because of its close proximity to Spokane, Washington. However, some people call it Long Lake, aft … |
| Kachess Lake, WA (North Central Washington, US West Region, USA, Washington) |
239,000 ac-ft | “Kachess” means “more fish,” a name that aptly describes Lake Kachess in North Central region of Washington. The lake is full of fish, and anglers can … |
| Keechelus Lake, WA (North Central Washington, US West Region, USA, Washington) |
157,900 ac-ft | (Also known as Lake Keechelus, Keechelus Reservoir) It is a picture postcard – snow capped mountains mirrored back in clean, clear, mountain water. Set against the backdrop of Washington’s Cascade Mount … |
| Moses Lake, WA (North Central Washington, US West Region, USA, Washington) |
131,000 ac-ft | Located where Washington State’s Pacific coast transforms into the arid desert of the eastern half, Moses Lake has over 6,800 acres of surface area en … |
| Coldwater Lake, WA (Southwest Washington, US West Region, USA, Washington) |
70,000 ac-ft | Today Coldwater Lake is a peaceful, scenic 750-acre lake, but the violence of Mount St. Helens created the lake in 1980. On May 18, 1980, a 5.1 magnit … |
| American Lake, WA (Seattle & Puget Sound Region, WA, US West Region, USA, Washington) |
60,000 ac-ft | Less than three miles inland from Puget Sound, American Lake is one of the lesser known vacation destinations in Washington’s Seattle-King County Regi … |