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The Gila River (; O'odham (): Keli Akimel or simply Akimel, Quechan: Haa Siʼil) is a tributary of the Colorado River flowing through New Mexico and Arizona in the United States. The river drains an arid watershed of nearly that lies mainly within the U.S. but also extends into northern Sonora, Mexico. Indigenous peoples have lived along the river for at least 2,000 years, establishing complex agricultural societies before European exploration of the region began in the 16th century. However, Euro-Americans did not permanently settle the Gila River watershed until the mid-19th century. During the 20th century, human development of the Gila River watershed necessitated the construction of large diversion and flood control structures on the river and its tributaries, and consequently the Gila now contributes only a small fraction of its historic flow to the Colorado.〔"The Gila is mostly bone dry in its lower reaches" (Jonathan Waterman, "American Nile: Saving the Colorado", ''National Geographic'').〕 The historic natural discharge of the river is around 1900 cfs, and is now only 247 cfs. These engineering projects have transformed much of the river valley and its surrounds from arid desert to irrigated land, and supply water to over five million people that live in the watershed. ==Geography== The Gila River has its source in western New Mexico, in Sierra County on the western slopes of Continental Divide in the Black Range. It flows southwest through the Gila National Forest and the Gila Cliff Dwellings National Monument, then westward into Arizona, past the town of Safford. After flowing along the southern slope of the Gila Mountains in Graham County through a series of canyons, the Gila is impounded by Coolidge Dam in San Carlos Lake south of Peridot. It emerges from the mountains into the valley southeast of Phoenix, Arizona, where it crosses the Gila River Indian Reservation as an intermittent stream due to large irrigation diversions. Well west of Phoenix, the river bends sharply southward along the Gila Bend Mountains, then it swings westward again near the town of Gila Bend. It flows southwestward between the Gila Mountains to the south and the Languna and Muggins ranges to the north in Yuma County, and finally it empties into the Colorado at Yuma, Arizona. The Gila is joined by many tributaries, beginning with the East and West Forks of the river, which combine to form the main stem near Gila Hot Springs in New Mexico. Above Safford, it is joined by the San Francisco River and the intermittent San Simon River. Further downstream it is joined by the San Carlos River from the north in San Carlos Lake. At Winkelman, Arizona it picks up the San Pedro River and then is joined by the Santa Cruz River south of Casa Grande. The Salt River, its main tributary, joins in the Phoenix metro area, and further west the Gila receives its last two major tributaries, the Agua Fria and Hassayampa Rivers, from the north. Although the Gila River flows entirely within the United States, the headwaters of two tributaries – the San Pedro and Santa Cruz Rivers – extend into Mexico. About , or 2.8% of the Gila's watershed, is in Mexico.〔(【引用サイトリンク】url=http://water.usgs.gov/GIS/huc_name.html )〕 A further or 5.7% lies within New Mexico, while the remaining majority, or 91.5%, is in Arizona. 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「Gila River」の詳細全文を読む スポンサード リンク
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