Question: The Snake River is a  tributary of which river on which Richland stands?

full_context: Document 1: Yakima Ridge: Yakima Ridge is a long anticline mountain ridge in Yakima County and Benton County in the U.S. state of Washington. From its western end just north of the city of Yakima, the ridge runs east-southeast through the Yakima Training Center to its eastern end at Hanford Reach National Monument and the Hanford Site. Yakima Ridge is paralled on the north by Umtanum Ridge and on the south by the Rattlesnake Hills. Moxee Valley and Black Rock Valley lie south of Yakima Ridge.
Document 2: Pacific Northwest: The Pacific Northwest (in the United States, commonly abbreviated as PNW), sometimes referred to as Cascadia, is a geographic region in western North America bounded by the Pacific Ocean to the west and (loosely) by the Cascade Mountain Range on the east. Though no agreed boundary exists, a common conception includes the U.S. states of Oregon and Washington and the Canadian province of British Columbia. Broader conceptions reach north into Alaska and Yukon, south into northern California and east to the Continental Divide, thus including Idaho, Western Montana, and western Wyoming. Idaho, Wyoming, and Montana are more accurately termed the Inland Northwest (INW), as the climate, folia, fauna, and politics are different than in the Pacific Northwest, as well as a different time zone in all but North Idaho. Narrower conceptions may be limited to the northwestern US or to the coastal areas west of the Cascade and Coast mountains. The variety of definitions can be attributed to partially overlapping commonalities of the region's history, geography, society, and other factors.
Document 3: Kootenay River: The Kootenay (Kootenai in the U.S. and historically called the Flatbow) is a major river in southeastern British Columbia, Canada and northern parts of the U.S. states of Montana and Idaho. It is one of the uppermost major tributaries of the Columbia River, which is the largest North American river that empties into the Pacific Ocean. The Kootenay River runs 781 km from its headwaters in the Kootenay Ranges of the Canadian Rockies, flowing from British Columbia's East Kootenay region into northwestern Montana, thence into northernmost Idaho Panhandle and returning to British Columbia in the West Kootenay region, where it joins the Columbia at Castlegar.
Document 4: Columbia, South Carolina: Columbia is the capital and second largest city of the U.S. state of South Carolina, with a population estimate of 134,309 as of 2016. The city serves as the county seat of Richland County, and a portion of the city extends into neighboring Lexington County. It is the center of the Columbia metropolitan statistical area, which had a population of 767,598 as of the 2010 United States Census, growing to 817,488 by July 1, 2016, according to 2015 U.S. Census estimates. The name "Columbia" is a poetic term used for the United States, originating from the name of Christopher Columbus.
Document 5: Columbia River: The Columbia River is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, Canada. It flows northwest and then south into the US state of Washington, then turns west to form most of the border between Washington and the state of Oregon before emptying into the Pacific Ocean. The river is 1243 mi long, and its largest tributary is the Snake River. Its drainage basin is roughly the size of France and extends into seven US states and a Canadian province. The fourth-largest river in the United States by volume, the Columbia has the greatest flow of any North American river entering the Pacific.
Document 6: Snake River: The Snake River is a major river of the greater Pacific Northwest in the United States. At 1078 mi long, it is the largest tributary of the Columbia River, the largest North American river that empties into the Pacific Ocean. Rising in western Wyoming, the river flows through the Snake River Plain of southern Idaho, then through the rugged Hells Canyon area via northeastern Oregon and the rolling Palouse Hills, to reach its mouth near the Washington Tri-Cities area, where it enters the Columbia. Its drainage basin encompasses parts of six U.S. states, and its average discharge is over 54000 cuft/s .
Document 7: Umtanum Ridge: Umtanum Ridge is a long anticline mountain ridge in Yakima County and Kittitas County in the U.S. state of Washington. It runs for approximately 55 miles east-southeast from the Cascade Range, through the Yakima Training Center to the edge of the Columbia River at Priest Rapids Dam and Hanford Reach. The eastern end of Umtanum Ridge enters Hanford Reach National Monument and the Hanford Site. Umtanum Ridge is paralleled on the north by Manastash Ridge and on the south by Yakima Ridge. The Yakima River cuts through the ridge at the Umtanum Ridge Water Gap.
Document 8: Hanford Site: The Hanford Site is a mostly decommissioned nuclear production complex operated by the United States federal government on the Columbia River in the U.S. state of Washington. The site has been known by many names, including: Hanford Project, Hanford Works, Hanford Engineer Works and Hanford Nuclear Reservation. Established in 1943 as part of the Manhattan Project in Hanford, south-central Washington, the site was home to the B Reactor, the first full-scale plutonium production reactor in the world. Plutonium manufactured at the site was used in the first nuclear bomb, tested at the Trinity site, and in Fat Man, the bomb detonated over Nagasaki, Japan.
Document 9: Missouri River: The Missouri River is the longest river in North America. Rising in the Rocky Mountains of western Montana, the Missouri flows east and south for 2341 mi before entering the Mississippi River north of St. Louis, Missouri. The river takes drainage from a sparsely populated, semi-arid watershed of more than half a million square miles (1,300,000 km), which includes parts of ten U.S. states and two Canadian provinces. When combined with the lower Mississippi River, it forms the world's fourth longest river system.
Document 10: Hanford Reach Interpretive Center: The Hanford Reach Interpretive Center, also known as The Reach Museum, is a museum and visitor center for Hanford Reach National Monument located in Richland, Washington. The center tells a story of the cultural, natural, and scientific history of the Hanford Reach and Columbia Basin area, as well as promoting tourism.
Document 11: Richland, Washington: Richland is a city in Benton County in the southeastern part of the State of Washington, at the confluence of the Yakima and the Columbia Rivers. As of the 2010 census, the city's population was 48,058. April 1, 2013, estimates from the Washington State Office of Financial Management put the city's population at 51,150. Along with the nearby cities of Pasco and Kennewick, Richland is one of the Tri-Cities, Washington, and is home to the Hanford nuclear site.
Document 12: Vancouver, Washington: Vancouver is a city on the north bank of the Columbia River in the U.S. State of Washington, and the largest suburb of Portland, Oregon. Incorporated in 1857, it is the fourth largest city in the state, with a population of 161,791 as of April 1, 2010 census. Vancouver is the county seat of Clark County and forms part of the Portland-Vancouver metropolitan area, the 23rd largest metropolitan area in the United States. Originally established in 1825 around Fort Vancouver, a fur-trading outpost, the city is located on the Washington–Oregon border along the Columbia River, directly north of Portland. In 2005, "Money" magazine named it No. 91 on its list of best places in America to live. In 2016, WalletHub ranks Vancouver the 39th best place to live for families in the US.
Document 13: Clark Fork River: The Clark Fork, or the Clark Fork of the Columbia River, is a river in the U.S. states of Montana and Idaho, approximately 310 mi long. The largest river by volume in Montana, it drains an extensive region of the Rocky Mountains in western Montana and northern Idaho in the watershed of the Columbia River. The river flows northwest through a long valley at the base of the Cabinet Mountains and empties into Lake Pend Oreille in the Idaho Panhandle. The Pend Oreille River in Idaho, Washington, and British Columbia, Canada which drains the lake to the Columbia in Washington, is sometimes included as part of the Clark Fork, giving it a total length of 479 mi , with a drainage area of 25820 sqmi . In its upper 20 mi in Montana near Butte, it is known as Silver Bow Creek. Interstate 90 follows much of the upper course of the river from Butte to northwest of Missoula. The highest point within the river's watershed is Mount Evans at 10641 ft in Deer Lodge County, Montana along the Continental Divide.
Document 14: Priest Rapids Dam: Priest Rapids Dam is a hydroelectric, concrete gravity dam; located on the Columbia River, between the Yakima Firing Range and the Hanford Nuclear Reservation, and bridges Yakima County and Grant County, in the U.S. state of Washington. The dam is 24 miles south of the town of Vantage, and 47 miles northwest of the city of Richland. It is located at mile marker 397.1 from the mouth of the Columbia. It is owned by the Grant County Public Utility District. Priest Rapids, for which the dam was named, are now submerged beneath the dam's reservoir.
Document 15: Mississippi River: The Mississippi River is the chief river of the second-largest drainage system on the North American continent, second only to the Hudson Bay drainage system. Flowing entirely in the United States (although its drainage basin reaches into Canada), it rises in northern Minnesota and meanders slowly southwards for 2320 mi to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains all or parts of 31 U.S. states and 2 Canadian provinces between the Rocky and Appalachian Mountains. The Mississippi ranks as the fourth-longest and fifteenth-largest river in the world by discharge. The river either borders or passes through the states of Minnesota, Wisconsin, Iowa, Illinois, Missouri, Kentucky, Tennessee, Arkansas, Mississippi, and Louisiana.
ground_truth: Columbia River