Editing Missouri River (section)

===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"/>