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of the Interior
Hungry Horse Dam is on the South Fork of the Flathead River, 15 miles south of the west entrance to Glacier National Park and 20 miles northeast of Kalispell, Montana. The damsite is in a deep, narrow canyon, approximately 5 miles southeast of the South Fork`s confluence with the main stem of the Flathead River. Hungry Horse Project is in the Flathead National Forest, Flathead County, Montana.
The project includes a dam and appurtenant works, reservoir, powerplant, and switchyard. At the time of its completion, the dam was the third largest dam, and the second highest concrete dam, in the world. The project plays an important role in the program for meeting the growing need for power in the Pacific Northwest and in the plans for providing a storage system for control of devastating floods. It also contributes to irrigation, navigation, and other uses.
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Hungry Horse is a key project in the Department of the Interior`s long-range program for multiple- purpose development of the water resources of the vast Columbia River drainage basin. The dam creates a large reservoir by withholding water in times of heavy runoff to minimize downstream flooding. This stored water is released for power generation when the natural flow of the river is low. Downstream power benefits are of major importance since more than five times as much power can be produced from water releases downstream than is produced at Hungry Horse Powerplant.
The 564-foot-high dam is a variable-thickness concrete arch structure with a crest length of 2,115 ft. The dam and appurtenant works contain 3,086,200 cubic yards of concrete. The spillway is the highest morning-glory structure in the world. Water cascading over the spillway rim drops a maximum distance of 490 feet. The capacity of the spillway is 50,000 cubic feet per second, and the reservoir has a total capacity of 3,468,000 acre-feet.
Power generating facilities are housed in a building with a structural steel framework surmounting a reinforced concrete substructure 394 feet long, 76 feet wide, and 157 feet high, constructed across the river channel at the downstream toe of the dam. The original design included four 71,250-kilowatt generators-a total of 285,000 kilowatts installed capacity. The generator capacity was uprated in the 1990`s to 107,000 kilowatts each for a total plant capacity of 428,000 kilowatts.
In 1995, a selective withdrawal system was installed on all four unit penstock intakes. This selective withdrawal system is used from the first of June to the end of September to increase the water discharge temperature to reduce the thermal shock for downstream fisheries and increasing aquatic insect communities for Bull Trout growth and reproduction.
The Flathead Valley was entered in the early 1800s by the Northwest Fur Company and the Hudson's Bay Company, which established trading posts north of Flathead Lake. The first permanent settler in the valley arrived in 1860.
Individual farmers irrigated the Ashley Creek area of the Flathead River Valley as early as 1885. The Ashley Irrigation District was formed in 1897 to serve 1,637 acres. In 1909, the Montana legislature passed a revised State irrigation district law and the Ashley Irrigation District was formed.
For a third of a century, Montana worked toward development of a project to harness the waters of the Flathead River for irrigation, flood control, and power. Original surveys in the drainage basin were initiated in 1921 by the Geological Survey. They were continued by the Bureau of Reclamation and other Federal agencies as a basis for seeking congressional approval of a project.
In June 1943, due to the wartime need for power, serious consideration was given to raising the level of Flathead Lake. This would have permitted the installation of additional capacity at Kerr Dam at Polson and would have firmed up the power production at the Thompson Falls, Grand Coulee, Rock Island, and Bonneville plants. Local opposition to this proposal, together with the need for multiple-purpose projects and war-emergency water storage for power production, gave impetus to serious consideration and investigations of constructing Hungry Horse Dam as an alternative.
Studies in 1977 evaluated the feasibility of additional generating capacity of about 200,000 kilowatts at the existing Hungry Horse Powerplant, including a new regulating dam downstream, and to increase the capacity of the present generators from 285,000 kilowatts to 360,000 kilowatts. In effect, the proposals then being considered would increase the at-site power generation from 285,000 to about 560,000 kilowatts. Other aspects of the studies included fish and wildlife, recreation, stream regulation, water quality, and flood control. These studies did not culminate in authorization.
Construction of Hungry Horse Dam was authorized by the Act of June 5, 1944 (58 Stat. 270, Public Law 78-329). The authorized purposes of the Hungry Horse Project are irrigation flood control, navigation, streamflow regulation, hydroelectric generation, and other beneficial uses.
The prime contract for the construction of Hungry Horse Dam and Powerplant was awarded April 21, 1948, and the work was completed July 18, 1953.
Hungry Horse Reservoir is located high in the Rocky Mountains, less than 30 miles from the Continental Divide, and is surrounded by more than 25 mountain peaks. The reservoir is about 34 miles long and offers excellent opportunities for fishing, boating, water skiing, and swimming. The surrounding mountains are popular big game hunting areas and several of the small tributaries to the reservoir have their headwaters in nearby alpine lakes. The reservoir area is located entirely within the boundaries of the Flathead National Forest, and the Forest Service administers recreational use of the reservoir. Facilities have been constructed for camping, picnicking, and boat launching.
Hungry Horse Project creates power benefits that extend from the Continental Divide westward to the Pacific Ocean. At-site production averages about a billion kilowatt-hours annually. The principal power benefit from the project arises from its ability to store water through the spring flood season for later release when needed. In an average year, this water will generate about 4.6 billion kilowatt-hours of power as it passes through a series of downstream powerplants.
Following the disastrous floods in the Columbia River Basin during the spring of 1948, which caused damage estimated at $100 million, the Hungry Horse Project was included in a main control plan system of reservoirs for control of floods in the basin. Hungry Horse Dam now contributes materially toward controlling floods on the Columbia River. The dam helped minimize floods in Flathead Valley and reduced peak discharges between the valley and Grand Coulee Dam by 10 to 25 percent, and at Portland, Oregon, by about 5 percent.
The Hungry Horse Reservoir has 2,982,000 acre feet of capacity assigned to flood control. The Hungry Horse Project has provided an accumulated $136,473,000 in flood control benefits from 1950 to 1998.