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The Sacramento River is the principal river of Northern California in the United States, and is the largest river in California. Rising in the Klamath Mountains, the river flows south for before reaching the Sacramento–San Joaquin River Delta and San Francisco Bay. The river drains about in 19 California counties, mostly within a region bounded by the Coast Ranges and Sierra Nevada known as the Sacramento Valley, but also extending as far as the volcanic plateaus of Northeastern California. Historically, its watershed has reached farther, as far north as south-central Oregon where the now, primarily, endorheic (closed) Goose Lake rarely experiences southerly outflow into the Pit River, the most northerly tributary of the Sacramento. The Sacramento and its wide natural floodplain were once abundant in fish and other aquatic creatures, notably one of the southernmost large runs of chinook salmon in North America. For about 12,000 years, native peoples have drawn upon the vast natural resources of the watershed, which had one of the densest American Indian populations in California. The river has also been used as a trade and travel route since ancient times. Hundreds of tribes sharing regional customs and traditions inhabited the Sacramento Valley, though they received little disturbance upon the arrival of Europeans in the 1700s. The Spanish explorer Gabriel Moraga named the river ''Rio de los Sacramentos'' in 1808, later shortened and anglicized into ''Sacramento''. In the 19th century the gold find in the Sierra Nevada was the impetus to the California Gold Rush with an enormous population influx. Overland trails such as the California Trail and Siskiyou Trail followed the Sacramento and other tributaries, guiding hundreds of thousands of people to the goldfields and the growing agricultural region of the Sacramento Valley. By the late part of the century, many populous communities had been established along the Sacramento River, chief of which was the city of Sacramento. Intensive agriculture and mining contributed to pollution in the Sacramento, and significant changes to the river's hydrology and environment. Since the 1950s the watershed have been intensely developed for water supply and the generation of hydroelectric power. Today, large dams impound the river and almost all of its major tributaries. The Sacramento is used heavily for irrigation and serves much of Central and Southern California through the canals of giant state and federal water projects. While now providing water to over half of California's population and supporting one of the most productive agricultural areas in the nation, these changes have left the Sacramento greatly modified from its natural state and have caused the decline of its once-abundant fisheries. ==Course== The Sacramento's source waters rise in the volcanic plateaus and ranges of far northern California as two streams – the Upper Sacramento and Pit. The main stem rises in the shadow of Mount Shasta and flows south through the Klamath Mountains, past Mount Shasta, Dunsmuir and Lakehead for about . However, the river's true headwaters lie far to the northeast, as the Pit River, which is formed by streams flowing southwest from the Modoc Plateau. The two rivers join in the waters of Lake Shasta, a giant reservoir formed by the Shasta Dam. The upper Sacramento is only the main stem by name: the flow of the Pit into the lake, , is nearly four times that of the Sacramento's . From the dam the Sacramento winds south through foothills and leaves the mountains near Redding, the first large city on the river's course and second largest on its entire course. Many small and moderate-sized tributaries join the river from both east and west including Clear, Cottonwood, Cow, Thomes, Ash and Battle Creeks. As the river meanders into the Central Valley a large portion of its flow is diverted into a pair of irrigation canals at Red Bluff. The Sacramento continues south, receiving Mill Creek near Tehama, and Stony and Big Chico creeks a bit southwest of Chico. The river then passes Colusa, and receives Butte Creek about west of the Sutter Buttes, a group of isolated volcanic hills in the middle of the Sacramento Valley.〔 Twenty-five miles (40 km) southeast of Colusa near Fremont Landing, the Sacramento incorporates the flow of its largest tributary, the Feather River, which descends from the Sierra Nevada to the northeast. About downstream, it flows into the city of Sacramento, California and receives the American River, its second largest tributary. Here the river splits into two: the main stem and the artificial Sacramento Deep Water Ship Channel. Both waterways continue south through the lowlands, eventually to rejoin in the estuary of the Sacramento–San Joaquin River Delta near Rio Vista.〔 The mouth of the Sacramento is on Suisun Bay near Antioch, where it combines with the San Joaquin River, south of the Montezuma Hills. The Sacramento is nearly a mile (2 km) wide at its mouth. The joined waters then flow west through the tidal marshes of Suisun Bay, the Carquinez Strait, San Pablo Bay and San Francisco Bay, whereupon the river's waters finally join the Pacific in the Golden Gate just to the north of San Francisco.〔 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「Sacramento River」の詳細全文を読む スポンサード リンク
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