page_title: Missouri River
section_title: Watershed
hierarchical_section_title: Missouri River / Watershed
context_page_description: 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 2,341 miles before entering the Mississippi River north of St. Louis, Missouri. The river drains a sparsely populated, semi-arid watershed of more than 500,000 square miles, which includes parts of ten U.S. states and two Canadian provinces. Although nominally considered a tributary of the Mississippi, the Missouri River above the confluence is much longer and carries a comparable volume of water. When combined with the lower Mississippi River, it forms the world's fourth longest river system.
  For over 12,000 years, people have depended on the Missouri River and its tributaries as a source of sustenance and transportation. More than ten major groups of Native Americans populated the watershed, most leading a nomadic lifestyle and dependent on enormous bison herds that roamed through the Great Plains. The first Europeans encountered the river in the late seventeenth century, and the region passed through Spanish and French hands before becoming part of the United States through the Louisiana Purchase.
context_section_description: With a drainage basin spanning 529,350 square miles (1,371,000 km²),
  the Missouri River's catchment encompasses nearly one-sixth of the area of the United States or just over five percent of the continent of North America. Comparable to the size of the Canadian province of Quebec, the watershed encompasses most of the central Great Plains, stretching from the Rocky Mountains in the west to the Mississippi River Valley in the east and from the southern extreme of western Canada to the border of the Arkansas River watershed. Compared with the Mississippi River above their confluence, the Missouri is twice as long and drains an area three times as large. The Missouri accounts for 45 percent of the annual flow of the Mississippi past St. Louis, and as much as 70 percent in certain droughts.
  In 1990, the Missouri River watershed was home to about 12 million people. This included the entire population of the U.S. state of Nebraska, parts of the U.S. states of Colorado, Iowa, Kansas, Minnesota, Missouri, Montana, North Dakota, South Dakota, and Wyoming, and small southern portions of the Canadian provinces of Alberta and Saskatchewan. The watershed's largest city is Denver, Colorado, with a population of more than six hundred thousand. Denver is the main city of the Front Range Urban Corridor whose cities had a combined population of over four million in 2005, making it the largest metropolitan area in the Missouri River basin. Other major population centers – mostly in the watershed's southeastern portion – include Omaha, Nebraska, north of the confluence of the Missouri and Platte Rivers; Kansas City, Missouri – Kansas City, Kansas, at the confluence of the Missouri with the Kansas River; and the St. Louis metropolitan area, south of the Missouri River just below the latter's mouth, on the Mississippi. In contrast, the northwestern part of the watershed is sparsely populated. However, many northwestern cities, such as Billings, Montana, are among the fastest growing in the Missouri basin.
  With more than 170,000 square miles (440,000 km²) under the plow, the Missouri River watershed includes roughly one-fourth of all the agricultural land in the United States, providing more than a third of the country's wheat, flax, barley and oats. However, only 11,000 square miles (28,000 km²) of farmland in the basin is irrigated. A further 281,000 square miles (730,000 km²) of the basin is devoted to the raising of livestock, mainly cattle. Forested areas of the watershed, mostly second-growth, total about 43,700 square miles (113,000 km²). Urban areas, on the other hand, comprise less than 13,000 square miles (34,000 km²) of land. Most built-up areas are along the main stem and a few major tributaries, including the Platte and Yellowstone Rivers.
  Elevations in the watershed vary widely, ranging from just over 400 feet (120 m) at the Missouri's mouth to the 14,293-foot (4,357 m) summit of Mount Lincoln in central Colorado. The river drops 8,626 feet (2,629 m) from Brower's Spring, the farthest source. Although the plains of the watershed have extremely little local vertical relief, the land rises about 10 feet per mile (1.9 m/km) from east to west. The elevation is less than 500 feet (150 m) at the eastern border of the watershed, but is over 3,000 feet (910 m) above sea level in many places at the base of the Rockies.
  The Missouri's drainage basin has highly variable weather and rainfall patterns, Overall, the watershed is defined by a Continental climate with warm, wet summers and harsh, cold winters. Most of the watershed receives an average of 8 to 10 inches (200 to 250 mm) of precipitation each year. However, the westernmost portions of the basin in the Rockies as well as southeastern regions in Missouri may receive as much as 40 inches (1,000 mm). The vast majority of precipitation occurs in summer in most of the lower and middle basin, although the upper basin is known for short-lived but intense summer thunderstorms such as the one which produced the 1972 Black Hills flood through Rapid City, South Dakota. Winter temperatures in t
caption: The Missouri in North Dakota, which was the furthest upstream that French explorers traveled on the river
exif: {}