Editing Missouri River (section)

==Watershed==
{{quote box
 |width=24em|bgcolor=|align=right
 |quote= There is only one river with a personality, a sense of humor, and a woman's caprice; a river that goes traveling sidewise, that interferes in politics, rearranges geography, and dabbles in real estate; a river that plays hide and seek with you today and tomorrow follows you around like a pet dog with a dynamite cracker tied to his tail. That river is the Missouri.<br/>{{right| — George Fitch<ref>{{harvp|Athearn|1965|p=89}}</ref>}}
}}

With a drainage basin spanning {{convert|529350|sqmi|km2}},<ref name="Story">{{cite web
 |url          = http://infolink.cr.usgs.gov/The_River/MORstory.htm
 |title        = The Missouri River Story
 |publisher    = U.S. Geological Survey
 |website      = Columbia Environmental Research Center
 |access-date  = April 10, 2010
 |archive-url  = https://web.archive.org/web/20100527124725/http://infolink.cr.usgs.gov/The_River/MORstory.htm
 |archive-date = May 27, 2010
 |url-status   = dead
 |df           = mdy-all
}}</ref>
the Missouri River's catchment encompasses nearly one-sixth of the area of the United States<ref>{{cite web
|url=http://www.cerc.usgs.gov/ScienceTopics.aspx?ScienceTopicId=10
|title=Missouri River
|publisher=U.S. Geological Survey
|website=Columbia Environmental Research Center
|date=September 8, 2009
|access-date=May 10, 2010
|archive-url=https://web.archive.org/web/20120619033247/http://www.cerc.usgs.gov/ScienceTopics.aspx?ScienceTopicId=10
|archive-date=June 19, 2012
|url-status=live
}}</ref> or just over five percent of the continent of North America.<ref>{{cite encyclopedia
|url=https://www.britannica.com/EBchecked/topic/418612/North-America
|title=North America
|encyclopedia=Encyclopædia Britannica
|access-date=May 10, 2010
|archive-url=https://web.archive.org/web/20120520211322/http://www.britannica.com/EBchecked/topic/418612/North-America
|archive-date=May 20, 2012
|url-status=live
}}</ref> 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{{efn|
The Mississippi River flows for approximately {{convert|1172|mi|km}} above St. Louis,<ref name="ACMEmapper"/> which is just over half of the Missouri's length.
}}
and drains an area three times as large.{{efn|
The Mississippi drains an area of {{cvt|172200|mi2|km2}} above the confluence with the Missouri River.<ref name="USGS"/>
}}
The Missouri accounts for 45&nbsp;percent of the annual flow of the Mississippi past St. Louis, and as much as 70&nbsp;percent in certain droughts.<ref name="missouriflow">{{cite web |url=http://wdr.water.usgs.gov/wy2009/pdfs/06934500.2009.pdf |title=USGS Gage #06934500 on the Missouri River at Hermann, Missouri: Water-Data Report 2009 |publisher=U.S. Geological Survey |website=National Water Information System |date=1897–2009 |url-status=dead |access-date=August 24, 2010 |archive-url=https://web.archive.org/web/20120402050034/http://wdr.water.usgs.gov/wy2009/pdfs/06934500.2009.pdf |archive-date=April 2, 2012}}</ref><ref name="MississippiStLouis">{{cite web |url=http://wdr.water.usgs.gov/wy2009/pdfs/07010000.2009.pdf |title=USGS Gage #07010000 on the Mississippi River at St. Louis, Missouri: Water-Data Report 2009 |publisher=U.S. Geological Survey |website=National Water Information System |date=1861–2009 |access-date=August 24, 2010 |archive-url=https://web.archive.org/web/20111104173450/http://wdr.water.usgs.gov/wy2009/pdfs/07010000.2009.pdf |archive-date=November 4, 2011 |url-status=dead}} Note: This gauge is just below the Missouri confluence, so the Missouri discharge was subtracted from {{convert|190000|cuft/s|m3/s}} to get this amount.</ref>

In 1990, the Missouri River watershed was home to about 12&nbsp;million people.<ref name="Story"/><ref name="MainstemSystem">
{{cite report
 |url=http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1070&context=usarmyceomaha
 |title=Missouri River Mainstem Reservoir System Master Water Control Manual
 |publisher=University of Nebraska |place=Lincoln, NE
 |via=Digital Commons, UNL
 |series=U.S. Army Corps of Engineers
 |date=January 1, 2006
 |access-date=January 15, 2012
 |archive-url=https://web.archive.org/web/20120516053439/http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1070&context=usarmyceomaha
 |archive-date=May 16, 2012
 |url-status=live
}}</ref> 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]].<ref name="Story"/> 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,<ref>
{{cite magazine
 |author=Crane, Gabe
 |year=2007
 |title=Wyoming metropolis?
 |magazine=Next American City
 |url=http://americancity.org/magazine/article/wyoming-metropolis-crane/
 |access-date=January 17, 2012
 |archive-url=https://web.archive.org/web/20101211074753/http://americancity.org/magazine/article/wyoming-metropolis-crane/
 |archive-date=December 11, 2010
}}
</ref> making it the largest metropolitan area in the Missouri River basin.<ref name="MainstemSystem"/> 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.<ref name="ACMEmapper"/> 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.<ref name="MainstemSystem"/>

With more than {{convert|170000|mi2|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 {{convert|11000|mi2|km2}} of farmland in the basin is irrigated. A further {{convert|281000|mi2|km2}} of the basin is devoted to the raising of livestock, mainly cattle. Forested areas of the watershed, mostly [[Second-growth forest|second-growth]], total about {{convert|43700|mi2|km2}}. Urban areas, on the other hand, comprise less than {{convert|13000|mi2|km2}} of land. Most built-up areas are along the main stem and a few major tributaries, including the Platte and Yellowstone Rivers.<ref name="MainstemSystem"/><ref>{{cite news
|author=DeFranco, Anthony
|title=No more floods! Build the Missouri River Development Project
|url=http://www.21stcenturysciencetech.com/Articles_2011/MissouriRiverProject.pdf
|website=21st Century Science and Technology
|series=New Federalist American Almanac 
|date=June 27, 1994
|access-date=January 17, 2012
|archive-url=https://web.archive.org/web/20120119203941/http://www.21stcenturysciencetech.com/Articles_2011/MissouriRiverProject.pdf
|archive-date=January 19, 2012
|url-status=live
}}</ref>

[[File:Missouri-bismarck-nd-2004-1.jpg|thumb|left|alt=The sun low over the horizon over a body of water surrounded by dark vegetation|The Missouri in [[North Dakota]], which was the furthest upstream that French explorers traveled on the river]]
Elevations in the watershed vary widely, ranging from just over {{convert|400|ft|m}} at the Missouri's mouth<ref name="GNIS"/> to the {{convert|14293|ft|m|adj=on}} summit of [[Mount Lincoln (Colorado)|Mount Lincoln]] in central Colorado.<ref>{{cite web |title=Mount Lincoln, Colorado |url=http://www.peakbagger.com/peak.aspx?pid=5793 |website=Peakbagger |access-date=May 21, 2014 |archive-url=https://web.archive.org/web/20140923083823/http://peakbagger.com/peak.aspx?pid=5793 |archive-date=September 23, 2014 |url-status=live}}</ref><ref>{{cite web
 |url=http://egsc.usgs.gov/isb/pubs/booklets/elvadist/elvadist.html#14,000 
 |title=Elevations and Distances in the United States 
 |publisher=U.S. Geological Survey 
 |website=Eastern Geographic Science Center 
 |date=April 29, 2005 
 |access-date=October 8, 2010 
 |url-status=dead 
 |archive-url=https://web.archive.org/web/20111015012701/http://egsc.usgs.gov/isb/pubs/booklets/elvadist/elvadist.html 
 |archive-date=October 15, 2011 
}}</ref> The river drops {{convert|8626|ft|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 {{convert|500|ft|m}} at the eastern border of the watershed, but is over {{convert|3000|ft|m}} above sea level in many places at the base of the Rockies.<ref name="ACMEmapper"/>

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 {{convert|8|to|10|in|mm}} of precipitation each year.<ref name="MainstemSystem"/> However, the westernmost portions of the basin in the Rockies as well as southeastern regions in Missouri may receive as much as {{convert|40|in|mm}}.<ref name="MainstemSystem"/> 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 [[thunderstorm]]s such as the one which produced the [[Black Hills flood|1972 Black Hills flood]] through [[Rapid City, South Dakota]].<ref>
{{cite report
|url=http://pubs.usgs.gov/fs/fs-037-02/
|title=The 1972 Black Hills-Rapid City Flood Revisited
|publisher=U.S. Geological Survey
|access-date=January 15, 2012
|author1=Carter, Janet M.
|author2=Williamson, Joyce E.
|author3=Teller, Ralph W.
|archive-url=https://web.archive.org/web/20120602034847/http://pubs.usgs.gov/fs/fs-037-02/
|archive-date=June 2, 2012
|url-status=live
}}
</ref> Winter temperatures in the northern and western portions of the basin typically drop to {{convert|&minus;20|°F|°C|1}} or lower every winter with extremes as low as {{convert|&minus;60|F|C|1}}, while summer highs occasionally exceed {{convert|100|°F|°C|1}} in all areas except the higher elevations of Montana, Wyoming and Colorado. Extreme maxima — almost all prior to 1960 — have exceeded {{convert|115|°F|°C|1}} in all US states in the basin.<ref name="MainstemSystem"/><ref>{{Cite web|url=https://www.weather.gov/|title=National Weather Service|archive-url=https://web.archive.org/web/20190413184557/https://www.weather.gov/|archive-date=April 13, 2019|url-status=live}}</ref>

As one of the continent's most significant river systems,<ref name="watershedmap">
{{cite web
 |title=Watersheds
 |type=map 
 |website=Commission for Environmental Cooperation 
 |year=2006 
 |url=http://www.cec.org/naatlas/img/NA-Watersheds.gif 
 |archive-url=https://wayback.archive-it.org/all/20080414101144/http://www.cec.org/naatlas/img/NA-Watersheds.gif 
 |url-status=dead 
 |archive-date=April 14, 2008 
 |access-date=September 12, 2008 
}}
</ref> the Missouri's drainage basin borders on many other major watersheds of the United States and Canada. The [[Continental Divide of the Americas|Continental Divide]], running along the spine of the Rocky Mountains, forms most of the western border of the Missouri watershed.<ref name="watershedmap"/> The [[Clark Fork (river)|Clark Fork]] and [[Snake River]], both part of the [[Columbia River]] basin, drain the area west of the Rockies in Montana, [[Idaho]] and western Wyoming. The Columbia, Missouri and [[Colorado River]] watersheds meet at [[Three Waters Mountain]] in Wyoming's [[Wind River Range]].<ref>
{{cite web
 |author=Gonzalez, Mark A. 
 |url=http://nationalatlas.gov/articles/geology/a_continentalDiv.html 
 |title=Continental Divides in North Dakota and North America 
 |website=The National Atlas 
 |series=North Dakota Geological Survey Newsletter 
 |year=2003 
 |access-date=January 14, 2012 
 |url-status=dead 
 |archive-url=https://web.archive.org/web/20080513163803/http://nationalatlas.gov/articles/geology/a_continentalDiv.html 
 |archive-date=May 13, 2008 
}}
</ref> South of there, the Missouri basin is bordered on the west by the drainage of the [[Green River (Colorado River)|Green River]], a tributary of the Colorado, then on the south by the mainstem of the Colorado. Both the Colorado and Columbia Rivers flow to the Pacific Ocean. However, a large [[endorheic|endorheic drainage]] called the [[Great Divide Basin]] exists between the Missouri and Green watersheds in western Wyoming. This area is sometimes counted as part of the Missouri River watershed, even though its waters do not flow to either side of the Continental Divide.<ref>{{cite web |url=http://www.wsgs.uwyo.edu/StratWeb/GreatDivideBasin/Default.aspx |title=Great Divide Basin |publisher=Wyoming State Geological Survey |access-date=March 16, 2011 |archive-url=https://web.archive.org/web/20110720105945/http://www.wsgs.uwyo.edu/StratWeb/GreatDivideBasin/Default.aspx |archive-date=July 20, 2011 |url-status=dead}}</ref>

To the north, the much lower [[Laurentian Divide]] separates the Missouri River watershed from those of the [[Oldman River]], a tributary of the [[South Saskatchewan River]], as well as the [[Souris River|Souris]], [[Sheyenne River|Sheyenne]], and smaller tributaries of the [[Red River of the North]]. All of these streams are part of Canada's [[Nelson River]] drainage basin, which empties into [[Hudson Bay]]. There are also several large endorheic basins between the Missouri and Nelson watersheds in southern Alberta and Saskatchewan.<ref name="watershedmap"/> The [[Minnesota River|Minnesota]] and [[Des Moines River|Des Moines]] Rivers, tributaries of the upper Mississippi, drain most of the area bordering the eastern side of the Missouri River basin. Finally, on the south, the [[The Ozarks|Ozark Mountains]] and other low divides through central Missouri, Kansas and Colorado separate the Missouri watershed from those of the [[White River (Arkansas)|White River]] and Arkansas River, also tributaries of the Mississippi River.<ref name="watershedmap"/>

===Major tributaries===
[[File:Yellowstone River, flowing through Paradise Valley.jpg|thumb|upright=1.1|alt=A river flows past grass-covered banks, trees are in the midground|The [[Yellowstone River]], the fifth longest tributary of the Missouri, which it joins in North Dakota]]
{{Main|List of tributaries of the Missouri River}}
Over 95 significant tributaries and hundreds of smaller ones feed the Missouri River, with most of the larger ones coming in as the river draws close to the mouth.<ref>{{cite web
|author=Stone, Clifton
|url=http://www3.northern.edu/natsource/HABITATS/Missio1.htm
|title=Missouri River
|publisher=Northern State University
|series=The Natural Source
|access-date=July 10, 2011
|archive-url=https://web.archive.org/web/20130523094749/http://www3.northern.edu/natsource/HABITATS/Missio1.htm
|archive-date=May 23, 2013
|url-status=dead
}}</ref> Most rivers and streams in the Missouri River basin flow from west to east, following the incline of the Great Plains; however, some eastern tributaries such as the James, [[Big Sioux River|Big Sioux]] and [[Grand River (Missouri)|Grand River]] systems flow from north to south.<ref name="MainstemSystem"/>

The Missouri's largest tributaries by runoff are the Yellowstone in Montana and Wyoming, the Platte in Wyoming, Colorado, and Nebraska, and the [[Kansas River|Kansas]]–[[Republican River|Republican]]/[[Smoky Hill River|Smoky Hill]] and Osage in Kansas and Missouri. Each of these tributaries drains an area greater than {{convert|50000|mi2|km2}} or has an average discharge greater than {{cvt|5000|cuft/s|m3/s}}.<ref name="USGS"/><ref name="USGSrivers"/> The Yellowstone River has the highest discharge, even though the Platte is longer and drains a larger area. In fact, the Yellowstone's flow is about {{cvt|13800|cuft/s|m3/s}}<ref name="Yellowstoneflow">
{{cite web
 |url         = http://www.sage.wisc.edu/riverdata/scripts/station_table.php?qual=32&filenum=2845
 |title       = Yellowstone River at Sidney, Montana
 |publisher   = Center for Sustainability and the Global Environment
 |website     = River Discharge Database
 |date        = 1965–1984
 |access-date = May 10, 2010
 |url-status  = dead
 |archive-url = https://web.archive.org/web/20051231072634/http://www.sage.wisc.edu/riverdata/scripts/station_table.php?qual=32&filenum=2845
 |archive-date = December 31, 2005
 |df          = mdy-all
}}
</ref> – accounting for sixteen percent of total runoff in the Missouri basin and nearly double that of the Platte.<ref name="Platteflow">{{cite web |url=http://wdr.water.usgs.gov/wy2009/pdfs/06805500.2009.pdf |title=USGS Gage #06805500 on the Platte River at Louisville, NE |publisher=U.S. Geological Survey |website=National Water Information System |date=1953–2009 |access-date=March 5, 2011 |archive-url=https://web.archive.org/web/20120319041013/http://wdr.water.usgs.gov/wy2009/pdfs/06805500.2009.pdf|archive-date=March 19, 2012|url-status=dead}}</ref> On the other end of the scale is the tiny [[Roe River]] in Montana, which at {{convert|201|ft|m}} long is one of the world's shortest rivers.<ref>{{harvp|McFarlan|McWhirter|1992|p=32}}</ref>
{{clear}}
{| class="wikitable sortable collapsible collapsed" style="float:right; width:47%;"
|-
!colspan="7"|Longest tributaries of the Missouri River
|- style="font-size:9pt; text-align:center;"
|Name
|colspan="2"|Length
|colspan="2"|[[Drainage basin|Watershed]]
|colspan="2"|[[Discharge (hydrology)|Discharge]]
|- style="font-size:9pt; text-align:center;"
! style="background:#faebd7;"|
! style="background:ivory;"|'''mi'''
!'''km'''
! style="background:ivory;"|'''mi<sup>2</sup>'''
!'''km<sup>2</sup>'''
! style="background:ivory;"|'''[[Cubic feet per second|ft<sup>3</sup>/s]]'''
!'''[[Cubic meters per second|m<sup>3</sup>/s]]'''
|- style="font-size:9pt; text-align:center;"
! scope="row" style="background:#faebd7;"|[[Platte River]]
| style="background:ivory;"|{{nts|1,061}}<ref name="ACMEmapper"/><ref name="USGSrivers">{{cite web |first=J.C. |last=Kammerer |url=http://pubs.usgs.gov/of/1987/ofr87-242/|title=Largest Rivers in the United States |publisher=U.S. Geological Survey |date=May 1990 |access-date=March 5, 2011|archive-url=https://web.archive.org/web/20170129040848/https://pubs.usgs.gov/of/1987/ofr87-242/ |archive-date=January 29, 2017 |url-status=live}}</ref>
|1,708
| style="background:ivory;"|{{nts|84,910}}<ref name="USGS">{{cite web |title=Boundary Descriptions and Names of Regions, Subregions, Accounting Units and Cataloging Units |url=http://water.usgs.gov/GIS/huc_name.html |publisher=U.S. Geological Survey |access-date=March 5, 2011 |archive-url=https://web.archive.org/web/20120427215107/http://water.usgs.gov/GIS/huc_name.html |archive-date=April 27, 2012 |url-status=live }}</ref>
|{{nts|219,900}}
| style="background:ivory;"|{{nts|7,037}}<ref name="Platteflow"/>
|199
|- style="font-size:9pt; text-align:center;"
! scope="row" style="background:#faebd7;"|[[Kansas River]]
| style="background:ivory;"|{{nts|749}}<ref name="USGSrivers"/><ref name="NationalMap">{{cite web|url=http://viewer.nationalmap.gov/viewer/ |title=The National Map |publisher=U.S. Geological Survey |access-date=March 5, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20120329155652/http://viewer.nationalmap.gov/viewer/ |archive-date=March 29, 2012 }}</ref>
|1,205
| style="background:ivory;"|{{nts|59,500}}<ref name="USGS"/>
|{{nts|154,000}}
| style="background:ivory;"|{{nts|7,367}}<ref>{{cite web |url=http://wdr.water.usgs.gov/wy2010/pdfs/06892350.2010.pdf |title=USGS Gage #06892350 on the Kansas River at DeSoto, KS |publisher=U.S. Geological Survey |website=National Water Information System |date=1917–2010 |access-date=March 5, 2011 |archive-url=https://web.archive.org/web/20120402050119/http://wdr.water.usgs.gov/wy2010/pdfs/06892350.2010.pdf |archive-date=April 2, 2012 |url-status=dead}}</ref>
|209
|- style="font-size:9pt; text-align:center;"
! scope="row" style="background:#faebd7;"|[[Milk River (Alberta–Montana)|Milk River]]
| style="background:ivory;"|{{nts|729}}<ref name="NationalMap"/>
|1,170
| style="background:ivory;"|{{nts|15,300}}<ref name="USGS"/>
|{{nts|39,600}}
| style="background:ivory;"|{{nts|618}}<ref>{{cite web |url=http://wdr.water.usgs.gov/wy2010/pdfs/06174500.2010.pdf |title=USGS Gage #06174500 on the Milk River at Nashua, MT |publisher=U.S. Geological Survey |website=National Water Information System |date=1940–2010 |access-date=March 5, 2011 |archive-url=https://web.archive.org/web/20130120022328/http://wdr.water.usgs.gov/wy2010/pdfs/06174500.2010.pdf |archive-date=January 20, 2013 |url-status=dead}}</ref>
|17.5
|- style="font-size:9pt; text-align:center;"
! scope="row" style="background:#faebd7;"|[[James River (Dakotas)|James River]]
| style="background:ivory;"|{{nts|710}}<ref name="NationalMap"/>
|1,140
| style="background:ivory;"|{{nts|21,500}}<ref name="USGS"/>
|{{nts|55,700}}
| style="background:ivory;"|{{nts|646}}<ref>{{cite web |url=http://wdr.water.usgs.gov/wy2009/pdfs/06478500.2009.pdf |title=USGS Gage #06478500 on the James River near Scotland, SD |publisher=U.S. Geological Survey |website=National Water Information System |date=1928–2009 |access-date=March 5, 2011 |archive-url=https://web.archive.org/web/20120402050132/http://wdr.water.usgs.gov/wy2009/pdfs/06478500.2009.pdf |archive-date=April 2, 2012 |url-status=dead}}</ref>
|18.3
|- style="font-size:9pt; text-align:center;"
! scope="row" style="background:#faebd7;"|[[Yellowstone River]]
| style="background:ivory;"|{{nts|702}}<ref name="ACMEmapper"/><ref>{{cite report |last=Miller |first=Kirk A. |url=http://pubs.usgs.gov/wri/wri984269/surwater.html |section=Surface Water |publisher=U.S. Geological Survey |title=Environmental Setting of the Yellowstone River Basin, Montana, North Dakota, and Wyoming |year=1999 |access-date=March 6, 2011 |archive-url=https://web.archive.org/web/20121018083021/http://pubs.usgs.gov/wri/wri984269/surwater.html |archive-date=October 18, 2012 |url-status=live}}</ref>
|1,130
| style="background:ivory;"|{{nts|70,000}}<ref name="USGS"/>
|{{nts|180,000}}
| style="background:ivory;"|{{nts|13,800}}<ref name="Yellowstoneflow"/>
|391
|- style="font-size:9pt; text-align:center;"
! scope="row" style="background:#faebd7;"|[[White River (Missouri River)|White River]]
| style="background:ivory;"|{{nts|580}}<ref name="NationalMap"/>
|933
| style="background:ivory;"|{{nts|10,200}}<ref name="Whiteflow">{{cite web|url=http://wdr.water.usgs.gov/wy2009/pdfs/06452000.2009.pdf|title=USGS Gage #06452000 on the White River near Oacoma, SD |publisher=U.S. Geological Survey |website=National Water Information System |date=1928–2009 |access-date=March 5, 2011 |archive-url=https://web.archive.org/web/20120402050145/http://wdr.water.usgs.gov/wy2009/pdfs/06452000.2009.pdf |archive-date=April 2, 2012 |url-status=dead}}</ref>
|{{nts|26,420}}
| style="background:ivory;"|{{nts|570}}<ref name="Whiteflow"/>
|16.1
|- style="font-size:9pt; text-align:center;"
! scope="row" style="background:#faebd7;"|[[Niobrara River]]
| style="background:ivory;"|{{nts|568}}<ref name="NationalMap"/>
|914
| style="background:ivory;"|{{nts|13,900}}<ref name="USGS"/>
|{{nts|36,000}}
| style="background:ivory;"|{{nts|1,720}}<ref>{{cite web|url=http://wdr.water.usgs.gov/wy2009/pdfs/06465500.2009.pdf|title=USGS Gage #06465500 on the Niobrara River near Verdel, NE |publisher=U.S. Geological Survey |website=National Water Information System |date=1928–2009 |access-date=March 5, 2011 |archive-url=https://web.archive.org/web/20120319041048/http://wdr.water.usgs.gov/wy2009/pdfs/06465500.2009.pdf |archive-date=March 19, 2012 |url-status=dead}}</ref>
|48.7
|- style="font-size:9pt; text-align:center;"
! scope="row" style="background:#faebd7;"|[[Little Missouri River (North Dakota)|Little Missouri River]]
| style="background:ivory;"|{{nts|560}}<ref name="NationalMap"/>
|900
| style="background:ivory;"|{{nts|9,550}}<ref name="USGS"/>
|{{nts|24,700}}
| style="background:ivory;"|{{nts|533}}<ref>{{cite web|url=http://wdr.water.usgs.gov/wy2009/pdfs/06337000.2009.pdf|title=USGS Gage #06337000 on the Little Missouri River near Watford City, ND |publisher=U.S. Geological Survey |website=National Water Information System |date=1935–2009 |access-date=March 5, 2011|archive-url=https://web.archive.org/web/20120402050138/http://wdr.water.usgs.gov/wy2009/pdfs/06337000.2009.pdf |archive-date=April 2, 2012 |url-status=dead}}</ref>
|15.1
|- style="font-size:9pt; text-align:center;"
! scope="row" style="background:#faebd7;"|[[Osage River]]
| style="background:ivory;"|{{nts|493}}<ref name="ACMEmapper"/>
|793
| style="background:ivory;"|{{nts|14,800}}<ref name="USGS"/>
|{{nts|38,300}}
| style="background:ivory;"|{{nts|11,980}}<ref>{{cite web |url=http://wdr.water.usgs.gov/wy2009/pdfs/06926510.2009.pdf|title=USGS Gage #06926510 on the Osage River below St. Thomas, MO |publisher=U.S. Geological Survey |website=National Water Information System|date=1996–2009|access-date=March 5, 2011 |archive-url=https://web.archive.org/web/20120402050203/http://wdr.water.usgs.gov/wy2009/pdfs/06926510.2009.pdf |archive-date=April 2, 2012 |url-status=dead}}</ref>
|339
|- style="font-size:9pt; text-align:center;"
! scope="row" style="background:#faebd7;"|[[Big Sioux River]]
| style="background:ivory;"|{{nts|419}}<ref name="NationalMap"/>
|674
| style="background:ivory;"|{{nts|8,030}}<ref name="USGS"/>
|{{nts|20,800}}
| style="background:ivory;"|{{nts|1,320}}<ref>{{cite web |url=http://wdr.water.usgs.gov/wy2010/pdfs/06485500.2010.pdf |title=USGS Gage #06485500 on the Big Sioux River at Akron, IA |publisher=U.S. Geological Survey |website=National Water Information System|date=1929–2009 |access-date=January 10, 2012 |archive-url=https://web.archive.org/web/20111028051239/http://wdr.water.usgs.gov/wy2010/pdfs/06485500.2010.pdf |archive-date=October 28, 2011 |url-status=dead}}</ref>
|37.4
|}

The table on the right lists the ten longest tributaries of the Missouri, along with their respective catchment areas and flows. Length is measured to the hydrologic source, regardless of naming convention. The main stem of the Kansas River, for example, is {{convert|148|mi|km}} long.<ref name="NationalMap"/> However, including the longest headwaters tributaries, the {{convert|453|mi|km|adj=on}} Republican River and the {{convert|156|mi|km|adj=on}} [[Arikaree River]], brings the total length to {{convert|749|mi|km}}.<ref name="NationalMap"/> Similar naming issues are encountered with the Platte River, whose longest tributary, the [[North Platte River]], is more than twice as long as its mainstream.<ref name="NationalMap"/>

The Missouri's headwaters above Three Forks extend much farther upstream than the main stem. Measured to the farthest source at Brower's Spring, the Jefferson River is {{convert|298|mi|km}} long.<ref name="MainstemSystem"/> Thus measured to its highest headwaters, the Missouri River stretches for {{convert|2639|mi|km}}. When combined with the lower Mississippi, the Missouri and its headwaters form part of the [[List of rivers by length|fourth-longest river system in the world]], at {{convert|3745|mi|km}}.<ref name="headwaters">
{{cite magazine
 |last1=Nell |first1=Donald F.
 |last2=Demetriades |first2=Anthony
 |date=July–August 2005
 |title=The true utmost reaches of the Missouri: Were Lewis and Clark wrong when they identified the source of this great river?
 |magazine=Montana Outdoors
 |url=http://fwp.mt.gov/mtoutdoors/HTML/articles/2005/MissouriSource.htm
 |access-date=January 14, 2012 |url-status=live
 |archive-url=https://web.archive.org/web/20120118010715/http://fwp.mt.gov/mtoutdoors/HTML/articles/2005/MissouriSource.htm
 |archive-date=January 18, 2012
}}</ref>

===Discharge===
[[File:Corp of Eng. 6-16-11A 267.JPG|thumb|Nebraska's [[Fort Calhoun Nuclear Generating Station]] was inundated when the Missouri River [[2011 Missouri River Floods|flooded in 2011]]|alt=Aerial view of farms and a power station in a rural area partly inundated by a river that has overflowed its banks]]
By [[Discharge (hydrology)|discharge]], the Missouri is the ninth largest river of the United States, after the Mississippi, [[St. Lawrence River|St. Lawrence]], [[Ohio River|Ohio]], Columbia, [[Niagara River|Niagara]], [[Yukon River|Yukon]], [[Detroit River|Detroit]], and [[St. Clair River|St. Clair]]. The latter two, however, are sometimes considered part of a strait between [[Lake Huron]] and [[Lake Erie]].<ref name="USrivers">
{{cite report
|last=Kammerer
|first=J.C.
|url=http://pubs.usgs.gov/of/1987/ofr87-242/
|title=Largest Rivers in the United States
|publisher=U.S. Geological Survey
|date=May 1990
|access-date=October 1, 2010
|archive-url=https://web.archive.org/web/20170129040848/https://pubs.usgs.gov/of/1987/ofr87-242/
|archive-date=January 29, 2017
|url-status=live
}}
</ref> Among rivers of North America as a whole, the Missouri is thirteenth largest, after the Mississippi, [[Mackenzie River|Mackenzie]], St. Lawrence, Ohio, Columbia, Niagara, Yukon, Detroit, St. Clair, [[Fraser River|Fraser]], [[Slave River|Slave]], and [[Koksoak River|Koksoak]].<ref name="USrivers"/><ref>
{{cite web
 |url=http://atlas.nrcan.gc.ca/site/english/learningresources/facts/rivers.html 
 |title=Rivers 
 |publisher=Natural Resources Canada 
 |website=The Atlas of Canada 
 |date=October 25, 2010 
 |access-date=November 28, 2010 
 |url-status=dead 
 |archive-url=https://web.archive.org/web/20070410230512/http://atlas.nrcan.gc.ca/site/english/learningresources/facts/lakes.html 
 |archive-date=April 10, 2007 
}}
</ref>

As the Missouri drains a predominantly semi-arid region, its discharge is much lower and more variable than other North American rivers of comparable length. Before the construction of dams, the river flooded twice each year – once in the "April Rise" or "[[Freshet|Spring Fresh]]", with the melting of snow on the plains of the watershed, and in the "June Rise", caused by snowmelt and summer rainstorms in the Rocky Mountains. The latter was far more destructive, with the river increasing to over ten times its normal discharge in some years.<ref>{{cite news
|author=Schneiders, Robert Kelley
|url=http://bismarcktribune.com/news/columnists/article_ede94e28-8df1-11e0-a6bc-001cc4c002e0.html
|title=The Great Missouri River Flood of 2011
|newspaper=Bismarck Tribune
|date=June 5, 2011
|access-date=January 14, 2012
|archive-url=https://web.archive.org/web/20110612030152/http://www.bismarcktribune.com/news/columnists/article_ede94e28-8df1-11e0-a6bc-001cc4c002e0.html
|archive-date=June 12, 2011
|url-status=live
}}</ref><ref>
{{cite report
 |url         = http://dnr.mo.gov/pubs/pub2018.pdf
 |title       = The Missouri River – Water Protection Program fact sheet
 |publisher   = Missouri Department of Natural Resources
 |access-date = January 14, 2012
 |url-status  = dead
 |archive-url = https://web.archive.org/web/20120513201159/http://dnr.mo.gov/pubs/pub2018.pdf
 |archive-date = May 13, 2012
 |df          = mdy-all
}}
</ref> The Missouri's discharge is affected by over 17,000 reservoirs with an aggregate capacity of some {{convert|141|e6acre-ft|km3}}.<ref name="MainstemSystem"/> By providing flood control, the reservoirs dramatically reduce peak flows and increase low flows. Evaporation from reservoirs significantly reduces the river's runoff, causing an annual loss of over {{convert|3|e6acre-ft|km3}} from mainstem reservoirs alone.<ref name="MainstemSystem"/>

{| style="float:left; width:15em; border:1=0px solid #a0a0a0; padding:0; background:#fff; text-align:center;"
|-
|
{| class="wikitable collapsible collapsed"
!colspan=3|Monthly discharge at<br />[[Hermann, Missouri|Hermann, MO]]<ref>{{cite web |url=http://nwis.waterdata.usgs.gov/nwis/monthly/?referred_module=sw&amp;site_no=06934500&amp;por_06934500_6=834553,00060,6,1928-10,2010-08&amp;format=html_table&amp;date_format=YYYY-MM-DD&amp;rdb_compression=file&amp;submitted_form=parameter_selection_list |title=USGS Gage #06934500 on the Missouri River at Hermann, Missouri: Monthly Average Flow |publisher=U.S. Geological Survey |website=National Water Information System |date=1957–2010 |access-date=October 8, 2010|archive-url=https://web.archive.org/web/20150920021706/http://nwis.waterdata.usgs.gov/nwis/monthly/?referred_module=sw&site_no=06934500&por_06934500_6=834553,00060,6,1928-10,2010-08&format=html_table&date_format=YYYY-MM-DD&rdb_compression=file&submitted_form=parameter_selection_list |archive-date=September 20, 2015 |url-status=dead}}</ref>
|-
!Month
![[Cubic feet per second|cfs]]
![[Cubic meters per second|m<sup>3</sup>/s]]
|-
|Jan.||52,400||1,490
|-
|Feb.||67,900||1,920
|-
|Mar.||96,300||2,730
|-
|Apr.||119,000||3,370
|-
|May||125,000||3,540
|-
|Jun.||124,000||3,510
|-
|Jul.||101,000||2,860
|-
|Aug.||73,600||2,080
|-
|Sep.||75,400||2,140
|-
|Oct.||76,500||2,170
|-
|Nov.||76,000||2,150
|-
|Dec.||61,000||1,730
|}

{| class="wikitable collapsible collapsed"
!colspan=3|Average discharge at<br />selected cities<br /><ref name="missouriflow"/><ref name="KSCdischarge"/><ref>{{cite web | title = Missouri River at Great Falls, Montana | publisher = Center for Sustainability and the Global Environment (SAGE), Gaylord Nelson Institute for Environmental Studies, University of Wisconsin |place=Madison, WI | work = River Discharge Database | url = http://www.sage.wisc.edu/riverdata/scripts/station_table.php?qual=32&filenum=1454 | archive-url = https://web.archive.org/web/20060902123108/http://www.sage.wisc.edu/riverdata/scripts/station_table.php?qual=32&filenum=1454 | url-status = dead | archive-date = September 2, 2006 | access-date = January 19, 2012 }}</ref><ref>{{cite web |url=http://wdr.water.usgs.gov/wy2010/pdfs/06440000.2010.pdf |title=USGS Gage #06440000 on the Missouri River at Pierre, SD |publisher=U.S. Geological Survey |website=National Water Information System|date=1934–1965 |access-date=January 19, 2012 |archive-url=https://web.archive.org/web/20111025013621/http://wdr.water.usgs.gov/wy2010/pdfs/06440000.2010.pdf |archive-date=October 25, 2011 |url-status=dead}}</ref><ref>{{cite web |url=http://wdr.water.usgs.gov/wy2009/pdfs/06486000.2009.pdf|title=USGS Gage #06486000 on the Missouri River at Sioux City, IA |publisher=U.S. Geological Survey |website=National Water Information System |date=1953–2009|access-date=October 9, 2010 |archive-url=https://web.archive.org/web/20120402050301/http://wdr.water.usgs.gov/wy2009/pdfs/06486000.2009.pdf |archive-date=April 2, 2012 |url-status=dead}}</ref><ref>{{cite web |url=http://wdr.water.usgs.gov/wy2009/pdfs/06610000.2009.pdf |title=USGS Gage #06610000 on the Missouri River at Omaha, NE |publisher=U.S. Geological Survey |website=National Water Information System |date=1953–2009 |access-date=October 9, 2010|archive-url=https://web.archive.org/web/20120402050344/http://wdr.water.usgs.gov/wy2009/pdfs/06610000.2009.pdf |archive-date=April 2, 2012 |url-status=dead}}</ref><ref>{{cite web |url=http://wdr.water.usgs.gov/wy2009/pdfs/06909000.2009.pdf|title=USGS Gage #06909000 on the Missouri River at Boonville, MO |publisher=U.S. Geological Survey |website=National Water Information System |date=1958–2009 |access-date=October 9, 2010 |archive-url=https://web.archive.org/web/20120421205723/http://wdr.water.usgs.gov/wy2009/pdfs/06909000.2009.pdf |archive-date=April 21, 2012 |url-status=dead}}</ref>
|-
!City
![[Cubic feet per second|cfs]]
![[Cubic meters per second|m<sup>3</sup>/s]]
|-
|[[Great Falls, Montana|Great Falls, MT]]
|10,300
|292
|-
|[[Pierre, South Dakota|Pierre, SD]]
|26,500
|750
|-
|[[Sioux City, Iowa|Sioux City, IA]]
|28,670
|812
|-
|[[Omaha, Nebraska|Omaha, NE]]
|32,190
|912
|-
|[[Kansas City, Missouri|Kansas City, MO]]
|55,400
|1,570
|-
|[[Boonville, Missouri|Boonville, MO]]
|67,160
|1,902
|-
|[[Hermann, Missouri|Hermann, MO]]
|87,520
|2,478
|}
|}

The [[United States Geological Survey]] operates fifty-one [[stream gauge]]s along the Missouri River. The river's average discharge at Bismarck, {{convert|1314.5|mi|km}} from the mouth, is {{cvt|21920|cuft/s|m3/s}}. This is from a drainage area of {{cvt|186400|mi2|km2}}, or 35% of the total river basin.<ref name="Bismarckdischarge">
{{cite web
|url=http://wdr.water.usgs.gov/wy2010/pdfs/06342500.2010.pdf
|title=USGS Gage #06342500 on the Missouri River at Bismarck, ND
|publisher=U.S. Geological Survey
|website=National Water Information System
|date=1954–2010
|access-date=January 9, 2012
|archive-url=https://web.archive.org/web/20111025012108/http://wdr.water.usgs.gov/wy2010/pdfs/06342500.2010.pdf
|archive-date=October 25, 2011
|url-status=live
}}</ref> At Kansas City, {{convert|366.1|mi|km}} from the mouth, the river's average flow is {{cvt|55400|cuft/s|m3/s}}. The river here drains about {{cvt|484100|mi2|km2}}, representing about 91% of the entire basin.<ref name="KSCdischarge">
{{cite web
|url=http://wdr.water.usgs.gov/wy2010/pdfs/06893000.2010.pdf
|title=USGS Gage #06893000 on the Missouri River at Kansas City, MO
|publisher=U.S. Geological Survey
|website=National Water Information System
|date=1958–2010
|access-date=January 9, 2012
|archive-url=https://web.archive.org/web/20111023221230/http://wdr.water.usgs.gov/wy2010/pdfs/06893000.2010.pdf
|archive-date=October 23, 2011
|url-status=live
}}</ref>

The lowermost gage with a period of record greater than fifty years is at [[Hermann, Missouri]] – {{convert|97.9|mi|km}} upstream of the mouth of the Missouri – where the average annual flow was {{cvt|87520|cuft/s|m3/s}} from 1897 to 2010. About {{cvt|522500|mi2|km2}}, or 98.7% of the watershed, lies above Hermann.<ref name="missouriflow"/> The highest annual mean was {{cvt|181800|cuft/s|m3/s}} in 1993, and the lowest was {{cvt|41690|cuft/s|m3/s}} in 2006.<ref name="missouriflow"/> Extremes of the flow vary even further. The largest discharge ever recorded was over {{cvt|750000|cuft/s|m3/s}} on July 31, 1993, during [[Great Flood of 1993|a historic flood]].<ref>{{cite web |url=http://nwis.waterdata.usgs.gov/nwis/peak?site_no=06934500&agency_cd=USGS&format=html |title=USGS Gage #07010000 on the Mississippi River at St. Louis, Missouri: Peak Streamflow |publisher=U.S. Geological Survey |website=National Water Information System |date=1844–2009 |access-date=August 24, 2010 |archive-url=https://web.archive.org/web/20140808044011/http://nwis.waterdata.usgs.gov/nwis/peak?site_no=06934500&agency_cd=USGS&format=html |archive-date=August 8, 2014 |url-status=dead}}</ref> The lowest, a mere {{cvt|602|cuft/s|m3/s}} – caused by the formation of an [[Ice jam|ice dam]] – was measured on December 23, 1963.<ref name="missouriflow"/>