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The Tuolumne River ( "To All o' Me"; Yokutsan: ''Tawalimnu'') flows for through Central California, from the high Sierra Nevada to join the San Joaquin River in the Central Valley. Originating at over above sea level in Yosemite National Park, the Tuolumne drains a rugged watershed of , carving a series of canyons through the western slope of the Sierra. While the upper Tuolumne is a fast-flowing mountain stream, the lower river crosses a broad, fertile and extensively cultivated alluvial plain. Like most other central California rivers, the Tuolumne is dammed multiple times for irrigation and the generation of hydroelectricity. Humans have inhabited the Tuolumne River area for up to 10,000 years. Prior to the arrival of Europeans, the river canyon provided an important summer hunting ground and a trade route between Native Americans in the Central Valley to the west and the Great Basin to the east. First named in 1806 by a Spanish explorer after a nearby indigenous village, the Tuolumne was heavily prospected during the California Gold Rush in the 1850s, and the lower valley was cultivated by American settlers over the next few decades. The city of Modesto grew up on the Tuolumne as a railroad hub, absorbing most of the population of the Tuolumne valley around the turn of the century. As agricultural production rose, farmers along the Tuolumne formed California's first two irrigation districts to better control and develop the river. From the 1900s to the 1930s, the river was dammed at Don Pedro and Hetch Hetchy to provide water for Central Valley farmers and the city of San Francisco, respectively. The Hetch Hetchy project, located inside Yosemite National Park, incited national controversy, and is widely regarded as the origin of the modern environmental movement.〔(【引用サイトリンク】title=A Century Later, the Battle for Hetch Hetchy Continues )〕 As the mid-20th century progressed, demands on the Tuolumne continued to increase, culminating in the completion of New Don Pedro Dam in the early 1970s. These projects halved the amount of water flowing from the Tuolumne into the San Joaquin, greatly reducing the once-abundant runs of salmon and steelhead in both rivers. ==Course== The Tuolumne originates in Yosemite National Park, high in the Sierra Nevada, as two streams. The Lyell Fork rises at the Lyell Glacier below Mount Lyell, the highest peak in Yosemite National Park,〔(【引用サイトリンク】title=Mount Lyell )〕 and flows north through Lyell Canyon. The 〔 Dana Fork originates between Mount Dana () and Mount Gibbs () and flows west.〔(【引用サイトリンク】title=Tuolumne River )〕 After the confluence of the forks in Tuolumne Meadows, the river meanders northwest, passing under Tioga Road. Although calm for the first few miles, this quickly changes as the river drops over Tuolumne Falls and White Cascades. After briefly passing through Glen Aulin, the river enters the spectacular Grand Canyon of the Tuolumne, where it forms three more major waterfalls – California, LeConte and Waterwheel Falls. Return and Piute Creeks join the river from the north within the Tuolumne Canyon. At the end of the canyon the river widens into Hetch Hetchy Reservoir, formed by a dam built in 1923 to provide water to the city of San Francisco, in the scenic Hetch Hetchy Valley. Falls Creek forms Wapama Falls and Tueeulala Falls, two of the highest in Yosemite, as it enters the reservoir from the north. From its source at above sea level in Tuolumne Meadows, the river drops nearly a mile (1.6 km) to the Hetch Hetchy reservoir at . Below the O'Shaughnessy Dam the Tuolumne passes Poopenaut Valley and enters a series of continuous canyons as it flows through the Sierra foothills, leaving the western boundary of Yosemite National Park and entering the Stanislaus National Forest. Most of the Tuolumne's main tributaries join within this reach, beginning with Cherry Creek from the north just below the intake of the Hetch Hetchy Aqueduct, which delivers water to San Francisco. The South Fork of the Tuolumne joins from the south a few miles downstream, near Groveland-Big Oak Flat, followed by the Clavey River from the north a few miles after that. The North Fork of the Tuolumne joins from the north near the upper end of Lake Don Pedro, which was formed in 1971 when the New Don Pedro Dam was built to provide hydroelectricity and irrigation water storage. Directly below Don Pedro Dam is the La Grange Dam, where about half the river's natural flow is diverted into the Turlock and Modesto Main Canals to irrigate over in the Central Valley.〔(【引用サイトリンク】title=MID Fast Facts )〕〔(【引用サイトリンク】title=Irrigation )〕 Leaving the foothills, the Tuolumne flows approximately west across the Central Valley to its confluence with the San Joaquin River, passing Waterford, Hughson, Empire, Ceres and Modesto. The lower Tuolumne is wide and slow-flowing, dropping just from the base of La Grange Dam to its mouth at . Highway 99 and the Southern Pacific Railroad tracks both cross the river in Modesto, and the Modesto Airport is located adjacent to the river shortly upstream. Dry Creek joins the Tuolumne from the north between the airport and the railroad. The confluence of the Tuolumne and San Joaquin is located in the San Joaquin River National Wildlife Refuge, about north of Grayson in Stanislaus County.〔(【引用サイトリンク】title=Dos Rios Ranch )〕 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「Tuolumne River」の詳細全文を読む スポンサード リンク
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