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Cataract Canyon is a long canyon of the Colorado River located within Canyonlands National Park and Glen Canyon National Recreation Area in Utah. It begins on the upstream end at the confluence with the Green River and ends at the confluence of the Dirty Devil River. The lower half of the canyon is submerged beneath Lake Powell when the lake is at its normal high water elevation of ==Whitewater rafting== Cataract Canyon is a popular whitewater rafting destination. The rapids in the canyon are generally considered "big water", with a character similar to those found in Grand Canyon. Cataract Canyon is rated on the river scale of one to five, unlike Grand Canyon which is rated on the scale of one to ten. Also unlike Grand Canyon, the flow of the Colorado River through Cataract Canyon is generally unregulated. The river flow can reach extreme levels during the spring runoff in years following plentiful snow throughout the Colorado River watershed. During an average spring runoff, the Colorado River will peak at approximately . The maximum recorded flow of occurred on May 27, 1984.〔(Historic Flows in Cataract Canyon ) National Park Service, Retrieved 2009-10-27〕 The rapids of Cataract Canyon become difficult at flows above and extreme at flows above .〔(High water videos of Cataract Canyon ) National Park Service, Retrieved 2009-10-27〕 Most rapids in Cataract Canyon are simply named from upstream to downstream as Rapid 1, Rapid 2, etc. However, some rapids within the canyon have separate names due to their location or notoriety. Particularly notorious are the "Big Drops", a set of three rapids in short succession named "Big Drop 1", "Big Drop 2" and "Big Drop 3". During high water, these three rapids essentially run together to form one very large rapid. These rapids contain many large hydraulic features including, "Little Niagara", "Satan's Gut",and "The Claw".〔 During times of high runoff, the National Park Service sometimes establishes a camp below the big drops and uses a jet boat to facilitate rescues of capsized rafts and their passengers. However,it is generally understood by seasoned river runners that all should 'self-rescue' and not depend on the NPS for support. Cataract Canyon historically contained several rapids which are currently submerged beneath Lake Powell and have been buried in lake sediment. Gypsum Canyon Rapid and Dark Canyon Rapid in particular were considered very difficult rapids to navigate. River trips which run Cataract Canyon must also run one of the flatwater sections above the confluence of the Green River and the Colorado River. Most groups launch at Potash (on the Colorado River) or Mineral Bottom (on the Green River) and spend up to 5 days on the river before entering Cataract Canyon. Motorized trips can make the trip into Cataract Canyon in substantially less time, often one day. In addition to the flatwater at the beginning of the trip, all groups must traverse Lake Powell before reaching the take-out at the Dirty Devil River or Hite Marina. Depending on the water level in Lake Powell, up to of lake water may be encountered by groups exiting the canyon. A number of commercial outfitters offer guided trips through Cataract Canyon. These trips vary in length between 1 day and 6 days and utilize both motorized and non-motorized vessels. Private groups are required to obtain a permit from the National Park Service prior to embarking on a Cataract Canyon trip.〔(Canyonlands National Park Permit Information ) Retrieved 2009-10-27〕 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「Cataract Canyon」の詳細全文を読む スポンサード リンク
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