Fish & wildlife Program Guide to Major Dams

 

Hydroelectricity in the Columbia River Basin 

Not long after Northwest pioneers established the first cities in the region, they began to capture the power of falling 

water to make electricity for their homes and industries. 

They were the first to tap the great hydroelectric potential of the Columbia River Basin, a region that includes parts of 

Washington, Oregon, Idaho, Montana, Wyoming, Utah, Nevada, and British Columbia. It is an area considerably larger 

than the country of France. 

Today, the Northwest relies on hydropower for about two-thirds of its electricity, and 40 percent of all U.S. hydropower 

comes from the Columbia system. 

The T.W. Sullivan Dam at Willamette Falls in Oregon City was 

the first hydroelectric dam in the lower Columbia Basin. It was 

built in 1888, 37 years after the founding of Portland. 

Washington Water Power Company built the Monroe Street 

Dam on the Spokane River in downtown Spokane in 1896, 

just 15 years after the city of Spokane Falls was platted and 

seven years after fire destroyed 32 blocks of the downtown 

business district. In Spokane, as elsewhere in the Northwest, 

hydroelectric power and progress were linked. 

The city of Idaho Falls built the first hydroelectric dam on the 

Snake River in 1904. The nearby Minidoka Dam, a federal 

project, followed in 1906. Development of other dams in the 

Columbia and Snake basins proceeded at a rather slow pace 

during the early 1900s. 

Hydroelectric development in the basin really began in earnest 

in the 1930s with the damming of the mainstem of the 

Columbia and Snake rivers. The first, in 1933, was Rock 

Island Dam near Wenatchee. Bonneville Dam followed in 

1938. Construction of dams on the Columbia and Snake rivers continued into the 1970s, with most of the development 

occurring between 1950 and 1970. 

Today there are 58 dams built exclusively for hydropower in the Columbia River Basin, and hydropower now supplies 

roughly 60 percent of the electricity used in the Northwest. Seventy-four percent of the power generating capacity in the

four states is hydropower, 32,950 megawatts of the 44,350 megawatts total. The mainstem of the Snake River not only 

has more dams than any other tributary in the Columbia Basin, it has the largest dams of any tributary in the basin. 

In addition to the 58 hydropower dams, there are 78 multiple purpose projects in the basin that include hydropower 

production. Other benefits provided by many of the dams include navigation for large barges; irrigation to farms in drier 

areas; launching areas for recreational activities; and flood control. 

While the dams brought tremendous advantages, they also posed problems to the region. They are obvious physical 

barriers to the salmon and steelhead that hatch in the tributaries and migrate through the mainstem Snake and 

Columbia to the ocean as juveniles, and back home to spawn as adults. 

In 1982, at the behest of Congress, the Northwest Power and Conservation Council adopted the Columbia River Basin 

Fish and Wildlife Program. It is designed to reverse some of the damage to fish and wildlife caused by hydropower and 

to increase protection in the future. 

The Council's program calls for permanent solutions to improve fish survival at dams, such as bypass systems to channel

juvenile fish migrating downstream away from the dams' turbines. 

Bypass systems are in place at dams downstream of Chief Joseph Dam on the Columbia and Hells Canyon Dam on the 

Snake. Those two dams do not have fish passage facilities. 

This map identifies the United States dams along the mainstem of the Columbia and Snake rivers. In addition to 

historical information, the map describes the dams and the types of fish protection facilities, including those for 

 

Willamette Falls Power Station, 1889

Oregon Historical Society photograph

(click to enlarge)

photo: willamette falls power station

 

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downstream and upstream fish passage. 

Dams (starting at mouth of Columbia, moving upriver) 

 

Bonneville Dam

Location: Bonneville, Oregon 

Columbia River mile: 146.1 

Operator: U.S. Army Corps of Engineers 

Type: Run of river dam and reservoir 

Completed: 1938 (Powerhouse I: 10 turbine units); 1982 (Powerhouse II: 8 

turbine units and 4 fishways) 

Generating capacity: 1,050 megawatts 

Juvenile fish passage facilities: Screens on all turbine units with a bypass 

system to tailwater. 

Adult fish passage facilities: Fish ladders with fish counting stations at both 

powerhouses. 

Additional notes: A juvenile bypass was completed in 1999 for powerhouse II. 

 

The Dalles Dam

Location: The Dalles, Oregon 

Columbia River mile: 191.5 

Operator: U.S. Army Corps of Engineers 

Type: Run of river dam and reservoir 

Completed: 1960 (14 turbine units); 1973 (8 turbine units) 

Generating capacity: 1,780 megawatts 

Juvenile fish passage facilities: Ice and trash sluiceway 

Adult fish passage facilities: Two fish ladders with fish counting stations 

Additional notes: Surface bypass system studies are ongoing at this project; 

however, spill and the ice and trash sluiceway will continue to be the primary 

juvenile passage routes 

 

John Day Dam

Location: Rufus, Oregon 

Columbia River mile: 215.6 

Operator: U.S. Army Corps of Engineers 

Type: Run of river dam and reservoir 

Completed: 1971 (16 turbine units) 

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Generating capacity: 2,1609 megawatts 

Juvenile fish passage facilities: Screens on all turbines with bypass system to 

tailwater 

Adult fish passage facilities: Two fish ladders with fish counting stations 

Additional notes: Between 1985 and 1987, the Corps installed screens in all 

powerhouse units 

 

McNary Dam

Location: Umatilla, Oregon 

Columbia River mile: 292 

Operator: U.S. Army Corps of Engineers 

Type: Run of river dam and reservoir 

Completed: 1957 (14 turbine units) 

Generating capacity: 980 megawatts 

Juvenile fish passage facilities: Screens on all units; bypass system to 

tailwater; fish collection and transportation facilities; fish run monitoring station 

Adult fish passage facilities: Two fish ladders with fish counting stations and 

adult PIT tag detection were installed in 2002 

Additional notes: McNary’s juvenile fish bypass system was completed in 1981, 

upgraded in 1994, and longer screens were installed in 1997. 

 

Priest Rapids Dam

Location: Near Mattawa, Washington 

Columbia River mile: 397.1 

Operator: Grant County Public Utility District No. 2 

Type: Run of river dam and reservoir 

Completed: 1961 (10 turbine units) 

Generating capacity: 955.6 megawatts 

Juvenile fish passage facilities: Spill and turbines provide good survival past 

the dam; flow management protects fall chinook in the Hanford Reach 

Adult fish passage facilities: Two fish ladders; fish counting and trapping 

facilities 

Additional notes: Grant County PUD’s relicensing studies identified new surface 

flow bypass systems, turbine passage improvements, and habitat and hatchery 

programs to offset losses 

 

Wanapum Dam

Location: Near Beverly, Washington 

Columbia River mile: 415.8 

Operator: Grant County Public Utility District No. 2 

Type: Run of river dam and reservoir 

Completed: 1964 (10 turbine units) 

Generating capacity: 1,038 megawatts 

Juvenile fish passage facilities: Spillway deflectors and top spill bulkhead 

installed 

Adult fish passage facilities: Two fish ladders with video fish counting facilities

Additional notes: Grant County PUD’s relicensing studies identified new surface 

flow bypass systems; turbine passage improvements; and habitat and hatchery 

programs to offset unavoidable losses 

 

Rock Island Dam

Location: Wenatchee, Washington 

Columbia River mile: 453.4 

Operator: Chelan County Public Utility District No. 1 

Type: Run of river dam and reservoir 

Completed: 1932 (Powerhouse I: 4 turbine units and house unit); 1953 

(Powerhouse I: 6 additional turbine units); 1979 (Powerhouse II: 8 turbine units)

Generating capacity: 624 megawatts 

Juvenile fish passage facilities: Gatewell bypass system with no screens at 

Powerhouse II. In addition, Chelan County PUD is evaluating a notched spillgate 

for providing downstream passage at the spillway. 

Adult fish passage facilities: Three fish ladders with counting stations 

Additional notes: Rock Island was the first dam built on the mainstem Columbia

River. Spill is an integral part of the long-term plan for safely providing fish 

passage at the project. 

Rocky Reach Dam

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Location: Wenatchee, Washington 

Columbia River mile: 473.7 

Operator: Chelan County Public Utility District No. 1 

Type: Run of river dam and reservoir 

Completed: 1961 (7 turbine units); 1971 (4 additional units) 

Generating capacity: 1,280 megawatts 

Juvenile fish passage facilities: Currently a bypass system with screens on 

two units and a surface collection system in the forebay cul-de-sac pass fish to a 

monitoring facility and the tailrace; spill is also provided if needed. 

Adult fish passage facilities: Fish ladder with fish counting station 

 

Wells Dam

Location: Azwell, Washington 

Columbia River mile: 515.8 

Operator: Douglas County Public Utility District No. 1 

Type: Run of river dam and reservoir 

Completed: 1967 (10 turbine units) 

Generating capacity: 774 megawatts 

Juvenile fish passage facilities: Wells Dam has a unique spillbay design which 

lies over the turbine intakes. The spillway was modified in 1991 to provide a 

bypass route for juvenile migrants. 

Adult fish passage facilities: Two fish ladders (one with trapping facility). Adult

PIT-tag detectors were evaluated in 2002, determined to be 100 percent efficient,

and were installed. 

Additional notes: The unique hydrocombine design of Wells Dam enables the 

spillway to function as an extremely efficient fish bypass system 

 

Chief Joseph Dam

Location: Bridgeport, Washington 

Columbia River mile: 545.1 

Operator: U.S. Army Corps of Engineers 

Type: Run of river dam and reservoir 

Completed: 1961 (16 turbine units); 1979 (11 turbine units) 

Generating capacity: 2,069 megawatts 

Fish passage facilities: (none) 

Additional notes: Chief Joseph and Grand Coulee dams lack any fish passage 

facilities and thus permanently block anadromous fish from the upper Columbia 

River Basin 

 

Grand Coulee Dam

Location: Grand Coulee, Washington 

Columbia River mile: 596.6 

Operator: U.S. Bureau of Reclamation 

Type: Dam and storage, reservoir, pumped storage reservoir 

Completed: 1941 (18 turbine units); 1982 ( 6 turbine units) 

Generating capacity: 6,620 megawatts 

Fish passage facilities: (none) 

Additional notes: See Chief Joseph Dam

 

Libby Dam

Location: River Mile 221.9 on the Kootenai (from the confluence with the 

Columbia River) 

Columbia River mile: 221.9 

Operator: U.S. Army Corps of Engineers 

Type: Dam and storage, reservoir 

Completed: 1973 

Generating capacity: 525 megawatts 

Fish passage facilities: (none) 

Additional notes: Libby Dam is a major upriver storage dam for the Columbia 

River hydropower system 

 

Hungry Horse Dam

Location: South Fork, Flathead River above Flathead Lake 

Columbia River mile: na 

Operator: U.S. Bureau of Reclamation 

Type: Dam and storage, reservoir 

Completed: 1953 

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Generating capacity: 428 megawatts (after renovations in progress) 

Fish passage facilities: (none) 

Additional notes: Hungry Horse Dam is the most upstream major storage 

project in the United States for the Columbia River hydroelectric system 

 

Ice Harbor Dam

Location: Pasco, Washington 

Snake River mile: 9.7 

Operator: U.S. Army Corps of Engineers 

Type: Run of river dam and reservoir 

Completed: 1962 (3 turbine units); 1976 (3 turbine units) 

Generating capacity: 603 megawatts 

Juvenile fish passage facilities: Intake screen bypass system was completed 

in 1993; spill is also provided 

Adult fish passage facilities: Two fish ladders with fish counting stations 

 

Lower Monumental Dam

Location: Kahlotus, Washington 

Snake River mile: 41.6 

Operator: U.S. Army Corps of Engineers 

Type: Run of river dam and reservoir 

Completed: 1970 (3 turbine units); 1978 (3 turbine units) 

Generating capacity: 810 megawatts 

Juvenile fish passage facilities: Intake screen bypass system completed in 

1992; collection and transport facilities; spill is also provided during the spring 

Adult fish passage facilities: Two Fish ladders 

 

Little Goose Dam

Location: Starbuck, Washington 

Snake River mile: 70.3 

Operator: U.S. Army Corps of Engineers 

Type: Run of river dam and reservoir 

Completed: 1970 (3 turbine units); 1978 (3 turbine units) 

Generating capacity: 810 megawatts 

Juvenile fish passage facilities: Extended screens on all units with bypass 

system to tailwater; collection and transportation facilities; spill is provided in the 

spring 

Adult fish passage facilities: Fish ladder 

 

Lower Granite Dam

Location: Almota, Washington 

Snake River mile: 107.5 

Operator: U.S. Army Corps of Engineers 

Type: Run of river dam and reservoir 

Completed: 1975 (3 turbine units); 1978 (3 turbine units) 

Generating capacity: 810 megawatts 

Juvenile fish passage facilities: Extended screens on all units with bypass 

system to tailwater; collection and transportation facilities; fish passage 

monitoring facility; spill is provided in the spring 

Adult fish passage facilities: Fish ladder, monitoring, and trap facilities 

 

Hells Canyon Dam

Location: Oxbow, Oregon 

Snake River mile: 247 

Operator: Idaho Power Company 

Type: Run of river dam and reservoir 

Completed: 1967 (3 turbine units) 

Generating capacity: 450 megawatts 

Fish passage facilities: (none) 

Additional notes: The Hells Canyon complex (Hells Canyon, Oxbow, and 

Brownlee projects) permanently blocks salmon from the upper Snake River Basin

 

Oxbow Dam

Location: Oxbow, Oregon 

Snake River mile: 273 

Operator: Idaho Power Company 

Type: Run of river dam and reservoir 

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Glossary 

Do bypass, spill, spillbay, tail race, forebay, etc., have you confused? Here’s a quick glossary.

attraction: Water flows designed to draw fish toward ladders or other bypass systems. 

bypass system, bypass channel: A structure in a dam that provides a route for fish to move through or around the 

dam without going through the turbine units. The bypass channel is the part of a system that includes a conduit built 

into the dam to pass fish. 

drawdown: Releasing water from a hydroelectric project to lower the reservoir elevation. Drawdowns are used for 

energy production or to create additional space in the reservoir to hold back floodwaters; to reduce the cross-sectional 

area of the reservoir, increasing the current to aid downstream fish passage; and to expose normally submerged 

structures for maintenance. 

fish guidance efficiency (FGE): The percentage of fish moving toward a dam’s turbine units that are diverted away 

by a fish guidance device, such as a submersible traveling screen. 

fish ladder: A series of ascending pools, similar to a staircase, that enables fish to migrate up the river past dams. 

Also called a fishway. 

fish passage efficiency: The percentage of fish passing a dam but avoiding the turbine units. 

fish sampling facility: A facility at a dam where some portion of the fish moving past the dam are collected 

periodically for research purposes. 

fish trapping or collection facility: A facility where juvenile fish are captured to be transported down the river 

Completed: 1961 (4 turbine units); 1978 (3 turbine units) 

Generating capacity: 220 megawatts 

Fish passage facilities: (none) 

Additional notes: See Hells Canyon Dam 

 

Brownlee Dam

Location: Cambridge, Idaho 

Snake River mile: 285 

Operator: Idaho Power Company 

Type: Dam and storage reservoir 

Completed: 1959 (4 turbine units); 1983 (1 turbine unit) 

Generating capacity: 675 megawatts 

Fish passage facilities: (none) 

Additional notes: Brownlee Reservoir is the major storage reservoir in the Hells 

Canyon complex 

 

Boundary Dam

Location: Near Metaline Falls, Washington 

Pend Oreille River mile: 17 

Operator: City of Seattle (City Light) 

Type: Dam and storage reservoir 

Completed: 1967 (4 units); 1985 (2 units) 

Generating capacity: 1,024 megawatts 

Fish passage facilities: (none) 

 

Dworshak Dam

Location: Ahsahka, Idaho 

Clearwater River (North Fork) mile: 1.9 (from confluence with the Snake 

River) 

Operator: U.S. Army Corps of Engineers 

Type: Dam and storage reservoir 

Completed: 1973 (3 turbine units) 

Generating capacity: 400 megawatts 

Fish passage facilities: (none) 

Additional notes: Dworshak Dam permanently blocks salmon and steelhead 

from the North Fork Clearwater River 

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(around the dams) or adult fish are culled to be taken to a hatchery. 

forebay: The part of a dam’s reservoir that is immediately upstream of the powerhouse. 

gatewell: The slot on the upstream face of a concrete dam where hydraulic gates are stored when not used to close 

the turbine intakes. (The gatewell also typically houses the fish screening device.) 

generating capacity: The maximum power that a power plant, such as a hydroelectric dam, can produce under 

specific conditions. 

hydraulic capacity: The maximum amount of water that can go through the powerhouse at a project. 

intake: The entrance to a turbine unit at a hydroelectric dam. 

lock: A chamber with watertight gates at each end used to lift or lower watercraft between the downstream tailrace 

water level and the upstream reservoir level. 

mainstem: The main channel of the river in a river basin, as opposed to the streams and smaller rivers that feed into 

it. In the fish and wildlife program, mainstem refers to the Columbia and Snake rivers. 

mid-Columbia: The section of the Columbia River below Chief Joseph Dam and above the river’s junction with the 

Snake River. 

Mid-Columbia Settlement Agreement: A process initiated by the Federal Energy Regulatory Commission, at the 

request of 

state and federal fishery agencies and Indian tribes, dealing with protection of migrating salmonids. FERC approved the 

first agreement among those parties and the 

Mid-Columbia PUDs in 1980. 

penstock: The pipe leading from the water intake to the hydraulic turbine. 

powerhouse: That part of a hydroelectric dam where the turbine-generators are housed and where power is produced 

by the action of the water on the turbine blades. 

pumped storage: A hydroelectric project designed to store electrical energy on a short-term basis. A pumped storage 

project is typically used to store electricity during nighttime periods of low demand for use during daily peak demand 

periods. 

river miles: Miles calculated from the mouth of the river or, for upstream tributaries, from the confluence with the 

main river. 

run-of-the-river dams: Hydroelectric dams without large reservoirs and, therefore, with only a limited capacity for 

water storage. This means they also have limited control of their outflow and power generation. 

sluiceway: A channel designed to collect ice and trash in the river (e.g., logs) before they get into the turbine units 

and cause damage. 

spill, spillbay: Releasing water out the spillbays rather than through the turbine units. The spillbay is the dam’s safety 

valve. Without it, excess water can damage the dam’s structure or overflow the dam. Dams without bypass systems 

spill water laden with fish to carry them away from turbines. 

storage dam: A dam with a large reservoir that can hold water over from the annual high-water season to the 

following low-water season. Of the major Columbia River Basin dams, the Grand Coulee, Brownlee, Dworshak, Hungry 

Horse, Libby, Round Butte, and Boundary dams are storage dams. 

submersible traveling screen (STS): A rotating screen, designed to fit into a dam’s turbine intake to divert fish up 

into bypass channels. 

tailrace: The canal or channel that carries water away from the dam. 

tailwater: The water surface immediately downstream from a dam. 

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