Dworshak Dam
Encyclopedia
Dworshak Dam is a hydroelectric, concrete gravity dam in Clearwater County
Clearwater County, Idaho
Clearwater County is a county located in the U.S. state of Idaho. Established in 1911, the county was named after the Clearwater River. As of the 2000 Census the county had a population of 8,930 . The county seat is Orofino....

, Idaho
Idaho
Idaho is a state in the Rocky Mountain area of the United States. The state's largest city and capital is Boise. Residents are called "Idahoans". Idaho was admitted to the Union on July 3, 1890, as the 43rd state....

, United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 on the North Fork Clearwater River
North Fork Clearwater River
The North Fork Clearwater River is a major tributary of the Clearwater River in the U.S. state of Idaho.From its headwaters in the Bitterroot Mountains of eastern Idaho, it flows southwest, north, then again southwest, and is dammed by the Dworshak Dam just above its mouth at the Clearwater in...

. The dam is located 4 miles (6 km) northwest of the city of Orofino
Orofino, Idaho
Orofino is a city in Clearwater County, Idaho, along Orofino Creek and the north bank of the Clearwater River. The population was 3,247 at the 2000 census, and the city is the county seat of Clearwater County...

, and 47 miles (76 km) east of Lewiston
Lewiston, Idaho
Lewiston is a city in and also the county seat of Nez Perce County in the Pacific Northwest state of Idaho. It is the second-largest city in the northern Idaho region, behind Coeur d'Alene and ninth-largest in the state. Lewiston is the principal city of the Lewiston, ID - Clarkston, WA...

. The dam is the highest straight-axis concrete dam in the Western Hemisphere
Western Hemisphere
The Western Hemisphere or western hemisphere is mainly used as a geographical term for the half of the Earth that lies west of the Prime Meridian and east of the Antimeridian , the other half being called the Eastern Hemisphere.In this sense, the western hemisphere consists of the western portions...

 and the 22nd highest dam in the world. Only two other dams in the U.S. exceed it in height.

History

Construction of Dworshak Dam began in June 1966. Originally, its name was slated to be "Bruces Eddy," but was changed to honor Henry C. Dworshak
Henry Dworshak
Henry Clarence Dworshak was a Republican United States Representative and a United States Senator from Idaho....

, a U.S. Senator
United States Senate
The United States Senate is the upper house of the bicameral legislature of the United States, and together with the United States House of Representatives comprises the United States Congress. The composition and powers of the Senate are established in Article One of the U.S. Constitution. Each...

 from Idaho from 1946-62.

The main structure was completed in 1972, with the generators coming online in 1973. Electrical generating capacity is 400 megawatts, with an overload capacity of 460 MW. There are two spillway gates. 6,500,000 cubic yards of concrete were used in the construction.

Dworshak Reservoir, the lake formed by the dam, initially reached full capacity on July 3, 1973.

In June 1980 the dam developed a leak through a 236 ft (71.9 m). long crack on the reservoir side. 7700 gallons per minute of water was sprayed past the powerhouse down into the river. The cost to fix the leak exceeded $1 million. The U.S. Army Corps of Engineers drilled seventy holes into the dam to intercept the crack, relieving pressure on the dam. A plastic sheet was then lowered over the crack. This reduced the flow by half. Additional repairs including a patch made of sawdust, cement and volcanic ash further reduced the flow to an acceptable level.

Controversy surrounded the construction project from the outset. Says Cort Conley in Idaho for the Curious, "There have always been more politicians than suitable damsites. Building the highest straight axis gravity dam in the Western Hemisphere, on a river with a mean flow of 5000 cuft/s, at a cost of $312 million, in the name of flood-control, is the second-funniest joke in Idaho. The funniest joke is inside the visitor center: a government sign entreats, "…help protect this delicate environment for future generations."

"The North Fork of the Clearwater was an exceptional river with a preeminent run of steelhead trout, and the drainage contained thousands of elk and white-tail deer. The Army Corps of Engineers proceeded to destroy the river, habitat, and fish; then acquired 5000 acres (20.2 km²) for elk management and spent $21 million to build the largest steelhead hatchery in the world, maintaining at a cost of $1 million dollars a year what nature had provided for nothing."

Operation

Dworshak Dam is part of the Columbia River Basin
Columbia River
The Columbia River is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, Canada, flows northwest and then south into the U.S. state of Washington, then turns west to form most of the border between Washington and the state...

 system of dams. The North Fork of the Clearwater River runs 2 miles (3 km) downstream from the base of the dam, where it joins the main Clearwater
Clearwater River (Idaho)
The Clearwater River is a river in north central Idaho, which flows westward from the Bitterroot Mountains along the Idaho-Montana border, and joins the Snake River at Lewiston. In October 1805, the Lewis and Clark Expedition descended the Clearwater River in dugout canoes, putting in at "Canoe...

, which flows into the Snake River
Snake River
The Snake is a major river of the greater Pacific Northwest in the United States. At long, it is the largest tributary of the Columbia River, the largest North American river that empties into the Pacific Ocean...

 at Lewiston
Lewiston, Idaho
Lewiston is a city in and also the county seat of Nez Perce County in the Pacific Northwest state of Idaho. It is the second-largest city in the northern Idaho region, behind Coeur d'Alene and ninth-largest in the state. Lewiston is the principal city of the Lewiston, ID - Clarkston, WA...

, and into the Columbia
Columbia River
The Columbia River is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, Canada, flows northwest and then south into the U.S. state of Washington, then turns west to form most of the border between Washington and the state...

 at Burbank, Washington
Burbank, Washington
Burbank is a census-designated place in Walla Walla County, Washington, United States, where the Snake River meets the Columbia. The population was 3,291 at the 2010 census. Named for Luther Burbank, the city is located just east of Pasco and Kennewick, across the Snake and Columbia Rivers,...

. The Dworshak Dam and Reservoir civil works project includes Dworshak Dam, the reservoir and surrounding Corps-managed lands, powerhouse, recreation facilities, wildlife mitigation and Dworshak National Fish Hatchery. Since 1972, $2,836,000 in potential flood damages have been prevented by the project.

Reservoir

Dworshak Reservoir is formed behind the dam. The reservoir stretches 86.2 kilometres (54 mi) upstream, and has 295 kilometres (183 mi) of steep shoreline. The maximum depth of the reservoir is 194 meters, with an average depth of 56 meters. The reservoir has a volume of 4.28 billion cubic meters when completely full, and a surface area of 6,644 hectares. Drawdowns of up to 47 meters reduce surface area as much as 52% to 3,663 hectares.

See also

  • Dworshak National Fish Hatchery
    Dworshak National Fish Hatchery
    Dworshak National Fish Hatchery is a "mitigation" hatchery located on the Clearwater River within the Nez Perce Reservation near Orofino, in north-central Idaho. It was constructed in 1969 by the Army Corps of Engineers, and is presently co-managed by the U.S. Fish and Wildlife Service and the Nez...

  • List of dams of the United States by height

External links

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