Instruct: Given a question, retrieve relevant documents that can help answer the question.
Query: How long is the American River in Northern California?
The American River (Río de los Americanos during the period before 1847 ruled by Mexico) is a 120-mile-long river in California that runs from the Sierra Nevada mountain range to its confluence with the Sacramento River in the Sacramento Valley. Via the Sacramento River, it is part of the San Francisco Bay watershed. This river is fed by the melting snowpack of the Sierra Nevada and its many headwaters and tributaries, including the North Fork American River, the Middle Fork American River, and the South Fork American River.
Historically, the American River, like many other rivers in California, were modified by the dams of beavers, until European trappers removed many of the beavers from their native habitat for their fur. Since the California Gold Rush was centered in an area that included the American River basin, it was one of the earlier California rivers to be populated, beginning at Leidesdorff Ranch, owned by William Leidesdorff. Water was used to drive grist mills. Gold miners dredged the riverbed and constructed diversion dams for hydraulic mining. Mining activity caused sediment and mercury waste to accumulate in the rivers. The Natoma Company completed its Folsom Powerhouse in 1895 and began delivering power 22 miles (35 km) away to the city of Sacramento to power a streetcar system.
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 the fertile agricultural 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 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.
Second only to the Columbia River on the west coast of the United States in Chinook salmon runs, the Sacramento and its tributaries once supported a huge population of this fish. Millions of salmon once swam upstream to spawn in the Sacramento; as recently as 2002 eight hundred thousand fish were observed to return to the river. The Sacramento and San Joaquin River systems are home to the southernmost existing run of chinook salmon in North America.
Below Rio Vista, the lower Sacramento River is rejoined by the Deep Water Ship Channel and the Yolo Bypass and curves southwest along the base of the Montezuma Hills, forming the border of Solano and Sacramento Counties. This part of the river is dredged for navigation by large oceangoing vessels and averages three-quarters of a mile (1.2 km) across. North of Antioch and Pittsburg, the Sacramento and San Joaquin Rivers join at the head of Suisun Bay, marking the official end of both rivers. The combined waters flow west through Suisun Bay and the Carquinez Strait into San Pablo Bay and San Francisco Bay, joining the Pacific at the Golden Gate.
North of Salmon, the river is joined by the North Fork, before turning west into over of continuous canyons through the Salmon River and Clearwater Mountains – some of the most rugged and isolated terrain in the contiguous United States. Exhibiting upwards of of vertical relief, the Salmon River canyons are some of the deepest in the U.S., surpassing the Grand Canyon and second only to the Snake River's Hells Canyon on the Idaho–Oregon border. Here, the river is joined by its two largest tributaries, the Middle Fork and South Fork. Ten miles (16 km) downstream (west) of its confluence with the Middle Fork, the Salmon River becomes the dividing line for the two time zones in Idaho: Mountain time to the south, Pacific time to the north, bisecting the state at approximately 45½ degrees north latitude.
The main source rivers include the Sacramento River from the north, the San Joaquin from the southeast, and the Calaveras and Mokelumne Rivers from the east. The Calaveras and Mokelumne are both tributaries of the San Joaquin River. The Sacramento and San Joaquin Rivers join at the western end of the Delta near Pittsburg, at the head of Suisun Bay, although they are linked upstream by the Georgiana Slough, which was first used by steamboats in the 19th century as a shortcut between Sacramento and Stockton. The southwestern part of the Delta is also transected by the Middle River and Old River, former channels of the San Joaquin. These rivers transport more than of water through the Delta each year – about 50 percent of all California's runoff.
The All-American Canal is an 80-mile (130 km) long aqueduct, located in southeastern California. It conveys water from the Colorado River into the Imperial Valley and to nine cities. It is the Imperial Valley's only water source, and replaced the Alamo Canal, which was located mostly in Mexico. The Imperial Dam, about 30 miles (48 km) northeast of Yuma, Arizona on the Colorado River, diverts water into the All-American Canal, which runs to just west of Calexico, California before its last branch heads mostly north into the Imperial Valley. Five smaller canals branching off the All American Canal move water into the Imperial Valley. These canal systems irrigate up to 630,000 acres (250,000 ha) of crop land and have made possible a greatly increased crop yield in this area, originally one of the driest on earth. It is the largest irrigation canal in the world, carrying a maximum of 26,155 cubic feet per second (740.6 m/s). Agricultural runoff from the All American Canal drains into the Salton Sea.
The city of American Fork is named after this river.
The description "American" in the river's name is to distinguish it from the Spanish Fork River that also originates in the Wasatch Range; alternatively, it could have been named after the American Fur Company.
In the coastal and southern parts of the state, and much of the Sacramento River system, the primary threat is rain floods in the November–April wet season. Oceanic "atmospheric river" or Pineapple Express storms can generate massive precipitation in a short period (often up to 50 percent of the total annual rainfall in just a few storms). This requires a certain safety margin to be maintained in reservoirs, which are often not allowed to capacity until late April or May. Shasta Lake, California's largest reservoir, is limited to approximately 71 percent of capacity in the winter in order to control rain flooding. Levees along Northern California rivers, such as the Sacramento and American rivers, are quite generously sized in order to pass large volumes of floodwater.
From Keswick Dam south to Red Bluff, California, the Sacramento River is relatively narrow and deep with some areas of broader alluvial floodplain. Most of the Chinook-salmon-spawning habitat in the river is located in this reach. The variability and magnitude of natural seasonal flows of the Sacramento River have been significantly altered for the purposes of irrigation and flood control. The dams and diversions operated by the Central Valley Project and local irrigation districts control much of the flow in the Sacramento River. Since 1993, to protect the holding and spawning of winter-run Chinook salmon, Reclamation has been required to manage cold-water reservoir storage and releases to maintain daily average water temperatures at or below between Keswick Dam and compliance locations between Balls Ferry and Bend Bridge, from May 15 to September 30.
The Stones River is composed of three major forks: the West, Middle, and East forks. The West Fork, long, rises in southernmost Rutherford County near the Bedford County line. The upstream portion of its course runs roughly parallel to U.S. Highway 231. The Middle Fork, long, rises in an area of low hills, or knobs, also near the line with Bedford County, near Hoovers Gap, an important troop movement route during the American Civil War. It flows roughly parallel to, but west of, Interstate 24 and U.S. Highway 41, and is met by the West Fork near State Route 99. The East Fork is the longest, at ; it rises in Cannon County on Short Mountain, an outlier of the Cumberland Plateau, and flows through Woodbury, the county seat. This stream is roughly paralleled by U.S. Route 70S.
The Columbia drains an area of about . Its drainage basin covers nearly all of Idaho, large portions of British Columbia, Oregon, and Washington, ultimately all of Montana west of the Continental Divide, and small portions of Wyoming, Utah, and Nevada; the total area is similar to the size of France. Roughly of the river's length and 85 percent of its drainage basin are in the US. The Columbia is the twelfth-longest river and has the sixth-largest drainage basin in the United States. In Canada, where the Columbia flows for and drains , the river ranks 23rd in length, and the Canadian part of its basin ranks 13th in size among Canadian basins. 
The Columbia shares its name with nearby places, such as British Columbia, as well as with landforms and bodies of water.
Cow Creek is a tributary of the Sacramento River in Shasta County, California. About long measured to its longest source, it drains a hilly, rural region at the northern end of the Sacramento Valley east of Redding. The creek begins at Millville at the confluence of Old Cow and South Cow Creek and flows west to Junction, where it turns south, joining the Sacramento near Anderson. Despite its name, Cow Creek is closer in size to a river, especially in winter when it is prone to large flash floods, accounting for up to 21 percent of the Sacramento's peak flows at Red Bluff.
Nine rivers in this list cross international boundaries or form them. Four—the Yukon, Columbia, Porcupine, and Kootenay—begin in Canada and flow into the United States. Five—the Milk, Pend d'Oreille, Saint Lawrence, Red, and Saint John—begin in the United States and flow into Canada. Of these, the Milk and the Kootenay cross the international border twice, the Milk leaving and then re-entering the United States, the Kootenay leaving and then re-entering Canada. The drainage basins of these nine rivers extend into both countries; in addition, the drainage basins of six others—the Fraser, Assiniboine, South Saskatchewan, Saskatchewan, Nelson, and Winnipeg—extend into the United States even though their main stems flow entirely within Canada.
The river is considered a prime habitat for Chinook salmon, Coho salmon, and rainbow trout. Once the river was the third-largest producer of salmon on the West Coast, after the Columbia and Sacramento Rivers, but the salmon run has been reduced since the construction of six dams between 1908 and 1962. Coho salmon in the Klamath River are listed as threatened under the Endangered Species Act. In 1963, the upper Trinity River—the largest single tributary to the Klamath—was virtually removed from the Klamath drainage with the completion of the Lewiston and Trinity Dams, diverting 90 percent of the upper Trinity's flow to the Sacramento Valley. From 1963 to 1991, only from the main stem above the dams was left to flow to the Klamath. In 1991, a minimum annual Trinity flow of was established, or about .
As the river continues south it approaches the Sacramento metro area, the largest population center in the watershed. Sacramento International Airport is located on the east bank of the river near Fremont. Near downtown Sacramento it receives the American River from the east, then passes under the historic Tower Bridge and Interstate 80. The California State Capitol sits less than half a mile (0.8 km) east of the river where the Tower Bridge crosses it. Shortly downstream, the Port of Sacramento is located on the west side of the Sacramento, connected to the river by a lock. The Sacramento River Deep Water Ship Channel provides access to the port from the Pacific, bypassing about of the winding lower Sacramento. The channel runs parallel to the Sacramento several miles to the west, and also forms the eastern boundary of the Yolo Bypass. The manually operated Sacramento Weir, located across from downtown Sacramento on the west side of the river, serves to relieve floodwater pressure from the American River by allowing it to drain west into the Yolo Bypass instead of continuing down the Sacramento River.
Downstream of Sacramento, the river enters the Sacramento–San Joaquin River Delta, a vast tidal estuary and inverted river delta of over which receives the entire run-off of the Central Valley, a region covering a third of California. The Sacramento is by far the largest contributor of fresh water to the Delta; in an average year, it accounts for more than 80 percent of the fresh water inflow. At Walnut Grove, the manmade Delta Cross Channel connects the Sacramento to the Mokelumne River channel, allowing a portion of the water to be pumped south toward Clifton Court Forebay, the receiving reservoir for the main CVP and State Water Project aqueducts which irrigate millions of acres and supply water to over 23 million people in the San Joaquin Valley, the San Francisco Bay Area and Greater Los Angeles. Although river levels are tidally influenced here and occasionally as far north as Verona, the water stays fresh in all but the driest years. Saltwater intrusion from the Pacific Ocean was one of the main reasons for the construction of the federal Central Valley Project (CVP), whose dams maintain a minimum flow in the Sacramento to keep seawater at bay.
The river has Oregon's longest covered bridge crossing it at Westfir, the Office Bridge. Portions of the river were designated wild and scenic in 1988. The portion from Waldo Lake to upstream from Westfir is designated "scenic" by the State of Oregon and is known for its native trout by fly fishermen.
The boundaries of California were defined by Spanish claims of Mexico, as part of the province of Alta California. The northern boundary of Spanish claims was set at 42 degrees latitude by the Adams–Onis Treaty of 1819. The states of Nevada and Utah, also originally part of Alta California, also use that line for their northern boundaries. The southern boundary, between California and Mexico, was established by the Treaty of Guadalupe Hidalgo that ended the Mexican–American War in 1848. The line is about 30 miles north of the former Alta California southern boundary. The eastern boundary consists of two straight lines: a north-south line from the northern border to the middle of Lake Tahoe, and a second line angling southeast to the Colorado River. From that point, south-southwest of Davis Dam on Lake Mohave, the southeast boundary follows the Colorado River to the international border west of Yuma. The eastern and south-eastern boundaries were decided upon during the debates of the California Constitutional Convention in 1849.
U.S. Route 101, or U.S. Highway 101 (US 101) is a north–south United States Numbered Highway that runs through the states of California, Oregon, and Washington, on the West Coast of the United States. It is also known as (The Royal Road) where its route along the southern and central California coast approximates the old trail which linked the Spanish missions, pueblos, and presidios. It merges at some points with California State Route 1 (SR 1).
The largest mountain ranges are the Andes and Rocky Mountains. The Sierra Nevada and the Cascade Range reach similar altitudes as the Rocky Mountains, but are significantly smaller. In North America, the greatest number of fourteeners are in the United States, and more specifically in the U.S. state of Colorado. The highest peaks of the Americas are located in the Andes, with Aconcagua of Argentina being the highest; in North America Denali (Mount McKinley) in the U.S. state of Alaska is the tallest.
The Middle Fork American River is one of the three main branches of the American River in Northern California. The river flows from its headwaters in the Sierra Nevada, in a generally southwest direction, to join the North Fork American River near Auburn.
The Maidu, Miwok, Nisenan, and Wintun peoples inhabited the American River in Sacramento for at least 5,000 years before Spaniards and Americans settled the region, although human habitation in Northern California is believed to date back as much as 12,000 years. They utilized the vast amount of resources of the American River for shelter, clothes, baskets, and other goods before Europeans arrived in the late 18th century. The Nisenan called the river "Kum Mayo", meaning "roundhouse river".
When it was open, the California Aqueduct Bikeway was the longest of the paved paths in the Los Angeles area, at long from Quail Lake near Gorman through the desert to Silverwood Lake in the San Bernardino Mountains. This path was closed in 1988 due to bicyclist safety and liability issues. It is expected to remain closed indefinitely due to the continued liability issues and an increased focus on security, especially after the September 11, 2001 attacks.
Two major river systems drain and define the two parts of the Central Valley. Their impact on the California Aqueduct is both direct and indirect. The Sacramento River, along with its tributaries the Feather River and American River, flows southwards through the Sacramento Valley for about . In the San Joaquin Valley, the San Joaquin River flows roughly northwest for , picking up tributaries such as the Merced River, Tuolumne River, Stanislaus River and Mokelumne River.
The Russian River, a southward-flowing river, drains 1,485 square miles (3,846 km) of Sonoma and Mendocino counties in Northern California. With an annual average discharge of approximately 1,600,000 acre feet (2.0 km), it is the second-largest river (after the Sacramento River) flowing through the nine-county Greater San Francisco Bay Area, with a mainstem 110 miles (177 km.) long.