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Black Eagle Dam is a hydroelectric gravity weir dam located on the Missouri River in the city of Great Falls, Montana.〔(Black Eagle Dam Open to Public," KFBB-TV, August 29, 2009. )〕〔"Black Eagle Falls (Black Eagle Dam) is the only one in the city." See: "Great Falls Scores a Number of Firsts in Montana." ''Great Falls Tribune.'' March 20, 2005.〕 The first dam on the site, built and opened in 1890, was a timber-and-rock crib dam.〔Peterson, p. 59.〕 This structure was the first hydroelectric dam built in Montana〔Marcosson, p. 145; Holmes, Dailey, and Walter, p. 397.〕〔(McCormick, p. 2. )〕 and the first built on the Missouri River.〔 The dam helped give the city of Great Falls the nickname "The Electric City."〔"City's Past Rooted in the River That Runs Through It." ''Great Falls Tribune.'' March 24, 2002.〕 A second dam, built of concrete in 1926 and opened in 1927, replaced the first dam (which was not removed and lies submerged in the reservoir).〔〔 Almost unchanged since 1926,〔 the dam is long and high,〔PPL Montana, Form S-4, p. A-23.〕 and its powerhouse contains three turbines capable of generating seven megawatts (MW) of power each.〔〔 The maximum power output of the dam is 18 MW.〔 Montana Power Company built the second dam, PPL Corporation purchased it in 1997 and sold it to NorthWestern Corporation in 2014. The reservoir behind the dam has no official name, but was called the Long Pool for many years.〔Peterson, p. 116.〕 The reservoir is about long,〔Peterson, p. 82.〕 and has a storage capacity of 〔("Black Eagle Dam," PPL Montana, 2011. ) Accessed 2011-04-05.〕 to of water.〔"The FERC order issuing a new license dated September 27, 2000, states that the Black Eagle reservoir has a storage capacity of 1820 AF at normal maximum water surface elevation of 3290 feet." See: (Water Right Solutions, Inc., p. 4. )〕 The dam is a "run-of-the-river" dam because it can generate electricity without needing to store additional water supplies behind the dam.〔 ==Black Eagle Falls== Black Eagle Falls is the first in a series of five waterfalls which constitute the Great Falls of the Missouri River in the state of Montana in the United States. Before being dammed, water dropped over the falls.〔Cutright and Johnsgard, p. 26.〕 Black Eagle Falls formed on a fall line unconformity in the Great Falls Tectonic Zone.〔 Botkin, p. 255.〕 The Missouri River in this area flows over and through the Kootenai Formation, a mostly nonmarine sandstone laid down by rivers, glaciers, and lakes in the past.〔(Fisher, p. 162. )〕 Some of the Kootenai Formation is marine, however, laid down by shallow seas.〔See, generally, Farshori and Hopkins, 1989; Haney and Schwartz, 2003.〕 The river is eating away at the softer nonmarine sandstone, with the harder rock forming the falls themselves. The Mandan and the South Piegan Blackfeet, among other Native Americans, knew of the falls.〔Robbins, 2008, p. 165; Howard, p. 16-17; Federal Writer's Project, p. 353.〕 On June 13, 1805, Meriwether Lewis of the Lewis and Clark Expedition became the first white person to see the Great Falls (the largest of the five waterfalls). On the second day that the expedition camped near the series of falls, Meriwether Lewis discovered Black Eagle Falls: :I arrived at another cataract of 26 feet. ... below this fall at a little distance a beatifull little Island well timbered is situated about the middle of the river. in this Island on a Cottonwood tree an Eagle has placed her nest; a more inaccessible spot I believe she could not have found; for neither man nor beast dare pass those gulphs which separate her little domain from the shores. the water is also broken in such manner as it descends over this pitch that the mist or sprey rises to a considerable height. this fall is certainly much the greatest I ever behald except those two which I have mentioned below. it is incomparably a geater cataract and a more noble interesting object than the celibrated falls of Potomac or Soolkiln &c.〔Lewis and Clark, p. 134-135 (grammar and punctuation in original).〕 It is unclear which member of the expedition named the falls, but the expedition called them "Upper Pitch."〔Cutright, p. 156.〕〔Howard, p. 66.〕 The falls were eventually named for the black eagle which Lewis saw on June 14, 1805.〔〔Vaughn, p. 83.〕 In 1872, Thomas P. Roberts, a survey engineer for the Northern Pacific Railway, formally named the cataract "Black Eagle Falls" after the incident recorded in Lewis' journal.〔Peterson, p. 20.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Black Eagle Dam」の詳細全文を読む スポンサード リンク
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