kimerajamm
Joined: 28 Nov 2010
Posts: 785
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 Posted: Tue Mar 01, 2011 4:34 pm Post subject: Bureau of Reclamation |
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The larger U.S. dams are owned and operated by the federal government (some by the Army Corps of Engineers and some by the Bureau of Reclamation), while the smaller dams are operated by public utility districts, and private power companies. The federally operated system is known as the Federal Columbia River Power System, which includes 31 dams on the Columbia and its tributaries. The system has altered the seasonal flow of the river in order to meet higher electricity demands during the winter. At the beginning of the 20th century, roughly 75 percent of the Columbia's flow occurred in the summer, between April and September. By 1980, the summer proportion had been lowered to about 50 percent, essentially eliminating the seasonal pattern.[114]
The installation of dams dramatically altered the landscape and ecosystem of the river. At one time, the Columbia was one of the top salmon-producing river systems in the world.[115] Previously active fishing sites, most notably Celilo Falls in the eastern Columbia River Gorge, have exhibited a sharp decline in fishing along the Columbia in the last century, and salmon populations have been dramatically reduced.[116] Fish ladders have been installed at some dam sites to help the fish journey to spawning waters. Chief Joseph Dam has no fish ladders and completely blocks fish migration to the upper half of the Columbia River system.[117]
[edit] Irrigation
A map shows the locations of many river dams on the Columbia River and its tributaries. They extend from near the river mouth in Oregon and Washington all the way up these rivers into Nevada, Idaho, Wyoming, Montana, and British Columbia.
Prominent dams of the Columbia River Basin. Color indicates dam ownership:
U.S. Federal government
Public Utilities
State, provincial, or local government
Private
The Bureau of Reclamation's Columbia Basin Project focused on the generally dry region of central Washington known as the Columbia Basin, which features rich loess soil.[12] Several groups developed competing proposals, and in 1933, President Franklin D. Roosevelt authorized the Columbia Basin Project. The Grand Coulee Dam was the project's central component; upon completion, it pumped water up from the Columbia to fill the formerly dry Grand Coulee, forming Banks Lake. By 1935, the intended height of the dam was increased from a range between 200 and 300 feet (61 and 91 m) to 500 feet (150 m), a height that would extend the lake impounded by the dam all the way to the Canadian border; the project had grown from a local New Deal relief measure to a major national project.[112]dental implants dentist sydney
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