As of 2023[update] , the U.S. state of Washington has 1,242 dams that are able to impound 10 acre-feet or more of water and are regulated by the Washington State Department of Ecology (DOE). These include dams that produce hydroelectricity and create reservoirs for irrigation, drinking water, or recreational uses. According to the DOE, approximately 52 percent of dams in the state are privately-owned, while 31 percent are owned by local governments.[ 1]
The Chief Joseph Dam , a concrete gravity dam on the Columbia River near Bridgeport, Washington
Approximately 87 percent of dams in Washington are earth fill dams , with the second most-common type being concrete gravity dams (6%). Only 113 dams in the state are taller than 50 feet (15 m). King County has 123 dams—the most of any county in the state.[ 1] The majority of dams were built between 1960 and 1999.[ 1] Proposals to remove underused dams and restore fish habitats emerged in the early 21st century with support from the state's Native American tribes; the first major dam removal was the Condit Dam near White Salmon in 2011, which was followed by two dams on the Elwha River near Port Angeles . As of 2024[update] , 39 dams in Washington have been removed.[ 2]
The largest dam in Washington, in terms of structural volume, reservoir capacity, and electricity production, is the Grand Coulee Dam on the Columbia River . It is the largest power station in the United States with a nameplate capacity of 6,809 megawatts and one of the largest concrete structures in the world.[ 3] The tallest dam is Mossyrock Dam on the Cowlitz River in Lewis County , at 606 feet (185 m).[ 4] The longest dam is O'Sullivan Dam on Crab Creek , at 19,000 feet (5,800 m); it is among the longest earth fill dams in the United States.[ 5]
Key
† Located on state border with Oregon
Dams and reservoirs in Washington over 25 feet (7.6 m)[ 1]
Dam
County
River
Reservoir
Type
Installed capacity (MW)
Height
Reservoir capacity
Year
Owner
Primary purpose(s)
ft
m
acre.ft
dam3
Alder Dam
Pierce /Thurston
Nisqually River
Alder Lake
Arch
50.0
330
100
241,950
298,440
1945
Tacoma Power
Hydroelectric
Bonneville Dam †
Skamania
Columbia River
Lake Bonneville
Gravity
1,242.0
197
60
537,000
662,000
1937
U.S. Army Corps of Engineers
Hydroelectric, Navigation
Boundary Dam
Pend Oreille
Pend Oreille River
Boundary Lake
Arch-gravity
1,070.0
340
100
95,000
117,000
1967
Seattle City Light
Hydroelectric
Box Canyon Dam
Pend Oreille
Pend Oreille River
Box Canyon Reservoir
Gravity
90.0
62
19
60,000
74,000
1956
Pend Oreille Public Utility District
Hydroelectric
Chief Joseph Dam
Douglas /Okanogan
Columbia River
Rock Island Pool
Gravity
2,620.0
135
41
516,000
636,000
1979
U.S. Army Corps of Engineers
Hydroelectric
Cle Elum Dam
Kittitas
Cle Elum River
Cle Elum Lake [ n 1]
Earthfill
165
50
436,900
538,900
1933
U.S. Bureau of Reclamation
Irrigation
Culmback Dam
Snohomish
Sultan River
Spada Lake
Rockfill
112.0
262
80
165,774
204,479
1965
City of Everett , Snohomish County PUD
Water supply
Cushman Dam No. 1
Mason
North Fork Skokomish River
Lake Cushman
Arch
43.2
235
72
453,400
559,300
1926
Tacoma Power
Hydroelectric
Cushman Dam No. 2
Mason
North Fork Skokomish River
Lake Kokanee
Arch
81.0
175
53
8,000
9,900
1930
Tacoma Power
Hydroelectric
Diablo Dam
Whatcom
Skagit River
Diablo Lake
Arch
129.0
389
119
88,500
109,200
1930
Seattle City Light
Hydroelectric
Dry Falls Dam [ n 2]
Grant
Grand Coulee
Banks Lake
Earthfill
123
37
1,275,000
1,573,000
1949
U.S. Bureau of Reclamation
Irrigation
Gorge Dam
Whatcom
Skagit River
Gorge Lake
Gravity
199.2
300
91
9,700
12,000
1961
Seattle City Light
Hydroelectric
Grand Coulee Dam
Grant /Okanogan
Columbia River
Franklin Delano Roosevelt Lake
Gravity
6,809.0
550
170
9,562,000
11,795,000
1942
U.S. Bureau of Reclamation
Irrigation, Hydroelectric, Flood control
Hiram M. Chittenden Locks and Dam
King
Lake Washington Ship Canal
Lake Washington [ n 3]
Gravity
0
26
7.9
458,000
565,000
1916
U.S. Army Corps of Engineers
Navigation
Howard A. Hanson Dam
King
Green River
Howard A. Hanson Reservoir
Earthfill
235
72
136,700
168,600
1961
U.S. Army Corps of Engineers
Flood control, Water supply
John Day Dam †
Klickitat
Columbia River
Lake Umatilla
Gravity
2,160.0
184
56
2,530,000
3,120,000
1971
U.S. Army Corps of Engineers
Hydroelectric, Navigation
Ice Harbor Dam
Franklin /Walla Walla
Snake River
Lake Sacajawea
Gravity
603.0
100
30
249,000
307,000
1962
U.S. Army Corps of Engineers
Hydroelectric, Navigation
Kachess Dam
Kittitas
Kachess River
Kachess Lake [ n 4]
Earthfill
112
34
239,000
295,000
1912
U.S. Bureau of Reclamation
Irrigation
Keechelus Dam
Kittitas
Yakima River
Keechelus Lake [ n 5]
Earthfill
128
39
157,900
194,800
1917
U.S. Bureau of Reclamation
Irrigation
LaGrande Dam
Pierce /Thurston
Nisqually River
LaGrande Reservoir
Gravity
65.0
192
59
2,700
3,300
1945
Tacoma Power
Hydroelectric
Lake Chelan Dam
Chelan
Chelan River
Lake Chelan [ n 6]
Gravity
59.2
40
12
677,400
835,600
1927
Chelan County Public Utility District
Hydroelectric
Lake Tapps (Multiple dikes)
Pierce
Off-stream
Lake Tapps
Earthfill
48,258
59,525
1911
Cascade Water Alliance
Recreation, Water supply (proposed)
Little Goose Dam
Columbia /Whitman
Snake River
Lake Bryan
Gravity
810.0
96
29
516,300
636,800
1970
U.S. Army Corps of Engineers
Hydroelectric, Navigation
Long Lake Dam
Lincoln /Stevens
Spokane River
Long Lake
Gravity
71.0
213
65
105,000
130,000
1915
Avista
Hydroelectric
Lower Baker Dam
Skagit
Baker River
Lake Shannon
Arch
79.0
285
87
161,470
199,170
1925
Puget Sound Energy
Hydroelectric
Lower Granite Dam
Garfield /Whitman
Snake River
Lower Granite Lake
Gravity
810.0
100
30
440,200
543,000
1975
U.S. Army Corps of Engineers
Hydroelectric, Navigation
Lower Monumental Dam
Franklin /Walla Walla
Snake River
Lake Herbert G. West
Gravity
810.0
100
30
432,000
533,000
1969
U.S. Army Corps of Engineers
Hydroelectric, Navigation
Masonry Dam
King
Cedar River
Chester Morse Lake /Masonry Pool [ n 7]
Arch-gravity
30.0
215
66
93,900
115,800
1915
Seattle Public Utilities
Water supply, Hydroelectric
Mayfield Dam
Lewis
Cowlitz River
Lake Mayfield
Arch-gravity
162.0
250
76
133,764
164,995
1963
Tacoma Power
Hydroelectric
McNary Dam †
Benton
Columbia River
Lake Wallula
Gravity
986.0
183
56
1,350,000
1,670,000
1954
U.S. Army Corps of Engineers
Hydroelectric, Navigation
Merwin Dam
Clark /Cowlitz
Lewis River
Lake Merwin
Arch-gravity
136.0
313
95
422,000
521,000
1931
PacifiCorp
Hydroelectric
Mossyrock Dam
Lewis
Cowlitz River
Riffe Lake
Arch
300.0
606
185
1,685,000
2,078,000
1968
Tacoma Power
Hydroelectric
Mud Mountain Dam
King
White River
Mud Mountain Lake
Earth/rockfill
0
432
132
106,000
131,000
1948
U.S. Army Corps of Engineers
Flood control
Pinto Dam
Grant
Off-stream
Billy Clapp Lake
Earthfill
130
40
21,200
26,100
1948
U.S. Bureau of Reclamation
Irrigation
Priest Rapids Dam
Grant /Yakima
Columbia River
Priest Rapids Lake
Gravity/ Embankment
955.6
178
54
237,100
292,500
1961
Grant County Public Utility District
Hydroelectric
Rock Island Dam
Chelan /Douglas
Columbia River
Rock Island Pool
Gravity
623.7
135
41
131,000
162,000
1933
Chelan County Public Utility District
Hydroelectric
Rocky Reach Dam
Chelan /Douglas
Columbia River
Lake Entiat
Gravity
1,299.6
130
40
382,000
471,000
1969
Chelan County Public Utility District
Hydroelectric
Ross Dam
Whatcom
Skagit River
Ross Lake
Arch
460.0
540
160
1,435,000
1,770,000
1949
Seattle City Light
Hydroelectric
Skookumchuck Dam
Thurston
Skookumchuck River
Skookumchuck Reservoir
Earthfill
1.0
190
58
34,800
42,900
1970
TransAlta
Water supply
South Fork Tolt River Dam
King
South Fork Tolt River
South Fork Tolt Reservoir
Earthfill
6.55
200
61
57,900
71,400
1964
Seattle Public Utilities
Water supply
Swift Dam
Skamania
Lewis River
Swift Reservoir
Earthfill
240.0
512
156
755,600
932,000
1958
PacifiCorp
Hydroelectric
The Dalles Dam †
Klickitat
Columbia River
Lake Celilo
Gravity
1,878.3
200
61
330,000
410,000
1957
U.S. Army Corps of Engineers
Hydroelectric, navigation
Tieton Dam
Yakima
Tieton River
Rimrock Lake
Earthfill
15.6
319
97
203,600
251,100
1925
U.S. Bureau of Reclamation
Irrigation
Toutle River Sediment Retention Structure
Cowlitz
North Fork Toutle River
[ n 8]
Earthfill
0
184
56
160,000
200,000
1989
U.S. Army Corps of Engineers
Sediment control
Upper Baker Dam
Whatcom
Baker River
Baker Lake
Arch
91.0
312
95
285,000
352,000
1959
Puget Sound Energy
Hydroelectric
Wanapum Dam
Grant /Kittitas
Columbia River
Lake Wanapum
Gravity/ Embankment
1,040.0
185
56
796,000
982,000
1963
Grant County Public Utility District
Hydroelectric
Wells Dam
Chelan /Douglas
Columbia River
Lake Pateros
Gravity
851.4
160
49
331,200
408,500
1967
Douglas County Public Utility District
Hydroelectric
Wynoochee Dam
Grays Harbor
Wynoochee River
Wynoochee Lake
Gravity
10.8
175
53
69,405
85,610
1972
City of Aberdeen
Water supply
Yale Dam
Clark /Cowlitz
Lewis River
Yale Lake
Earthfill
134.0
323
98
402,000
496,000
1953
PacifiCorp
Hydroelectric
^ Natural lake raised by dam.
^ Holds Banks Lake along with the smaller North Dam .
^ Natural lake with its ocean outlet re-routed via the ship canal. The lock and dam structure maintains the lake level.
^ Natural lake raised by dam.
^ Natural lake raised by dam.
^ Natural lake raised by dam.
^ Chester Morse Lake is a natural lake enlarged by the Chester Morse Dam in 1900. When Masonry Dam was constructed in 1915 it submerged the old dam and created a new body of water, just downstream and connected to Chester Morse Lake, called Masonry Pool.
^ The Sediment Retention Structure was constructed to trap debris flow sediment after the 1980 eruption of Mount St. Helens . The basin behind the dam is almost entirely filled with silt.
^ a b c d Inventory of Dams Report (PDF) (Report). Washington State Department of Ecology . December 2023. Retrieved November 14, 2024 .
^ a b c Bartoo-Smith, Nika; Breda, Isabella (July 7, 2024). "Why 'deadbeat dam' removals are so difficult in WA, PNW" . The Seattle Times . Retrieved November 14, 2024 .
^ "Grand Coulee Dam Statistics and Facts" (PDF) . United States Bureau of Reclamation . December 2021. Retrieved November 14, 2024 .
^ Holden Givens, Linda (June 2, 2022). "Mossyrock — Thumbnail History" . HistoryLink . Retrieved November 14, 2024 .
^ Tate, Cassandra (August 31, 2005). "Columbia National Wildlife Refuge" . HistoryLink . Retrieved November 14, 2024 .