Mississippi River

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Satellite photo of the Mississippi River Delta. Source: NASA

The Mississippi River drains the largest river basin in North America, and is one of the major rivers of the world.

The Mississippi River watershed is the fourth largest in the world, extending from the Allegheny Mountains in the east to the Rocky Mountains in the west. The watershed includes all or parts of 31 states and two Canadian provences. The watershed measures approximately 1.2 million square miles (3.1 million square kilometers), covering about 40% of the lower 48 states. The Mississippi drains most of the United States between the Appalachian Mountains in the east and the Rocky Mountains in the West.

The mainstream of the Mississippi River has headwaters rising at Lake Itasca, Minnesota and flows approximately 2340 miles (3765 km). Though the longest part of the river includes the the Missouri River which flows approximately 2540 miles (4088 km) before joining the Mississippi near its mid-point, north of the city of St Louis. Correspondingly, the total river length, that includes the Missouri River conjoined with the mainstem Mississippi River, is 3902 miles (6310 km).Large rivers which flow into the Mississippi River including the Ohio, Cumberland, Tennessee, Missouri, Arkansas, and Red rivers.

Significant sediment load, nitrate and pesticides are carried along by the enormous flow of the Mississippi. The Mississippi Basin is a locus of very early sedentary agriculture in North America, and boasts sites of some of the early mound building Native American tribes. The first European record of the Mississippi was recorded by Spanish explorer Fernando de Soto on May 8, 1541.

Natural fluvial processes in the Mississippi Delta are increasing the flow of a distributary, the Atchafalya River; without ongoing engineering works, the Atchafalaya would take over most of the mainstem flow and render the port of New Orleans defunct.


The drainage basin of the Mississippi spans an area of approximately 2,981,080 square kilometers. The length of the Mississippi River is about 4070 kilometers, and the principal tributaries are the Ohio River, Missouri River, Red River and Arkansas River. The average discharge at Pilottown, near Baton Rouge is about 16,790 cubic meters per second.

The Atchafalaya River is an important distributary of the Mississippi River; moreover, this 220 kilometer long navigable river is gradually assuming a greater proportion of the flow of the Mississippi River. In fact, taxpayers in the USA are subsidizing an ongoing preservation of flow favoring the Mississippi channel, such that natural processes would render the Mississippi present mainstem un-navigable without these ongoing subsidized public works to favor the Mississippi flow over the Atchafalaya. Without these ongoing interventions, the seaport of New Orleans would cease to exist in the relatively near future.
Source: Wikimedia Commons

Water quality

Water quality has experienced challenges in the Mississippi River over the last century and continuing to present day, chiefly due to agricultural runoff (Surface runoff). In particular, nitrate loading is high along the entire lower Mississippi, and especially deleterious in the delta reach. High nitrate and other water pollution at the river mouth has created a dead zone in the waters of the Gulf of Mexico, which zone extends to a considerable distance from the mouth itself. Computer modeling indicates that nitrate loads could be reduced by one third, if agricultural nitrate fertilizers are cut by merely 12 percent.

The Mississippi River drains about forty percent of the landmass of the coterminous USA; however, the Mississippi conveys around two thirds of all sediment delivered from this USA coterminous state landmass to all oceans. This sediment load has been building complex deltaic structures for at leas the last 6000 years; moreover, since circa 1500 AD, the sediment load has concentrated upon deposition in the Balize Delta.

In the year 1900, the Chicago Sanitary and Ship Canal was constructed to enhance water transport between Lake Michigan and the Mississippi; moreover, this canal was also used to discharge Chicago’s massive sewage wastes, so that Chicago's drinking water source would be relieved of most of this wastewater.

Historically since the 1950s pesticides heptachlor and endrin have caused fish kills in the Mississippi; more recently phenol concentrations have been measured at elevated levels. Other pesticides and herbicides have been found consistently in the Mississippi waters, notably atrazine, cyanazine and alachlor which have occurred at levels above federal water quality standards.

See also:

Flooding and engineering works

Great Flood of 1927. U.S.Coast and Geodetic Survey
Since the 1800s engineering works began on the upper Mississippi, including locks and lakes chiefly to abet navigation north of St. Louis. By the beginning of the twentieth century numerous levee projects commenced south of St. Louis in order to channelize the Mississippi, in attempts to protect farmland and urban development along the river. These efforts were in many ways an uphill fight to contain a mighty river that had meandered for 10,000 years across a broad lowland floodplain.

An unintended consequence was development of greater flooding in the downstream areas by depriving the great river of ample holding areas in the erstwhile swampy lower Mississippi. This river levee construction combined with massive interference with the natural tendency of the Atchafalya to capture more flow have rendered the delta area and New Orleans more vulnerable to flooding events. Consequently the stage was set for potentially costly flooding to the city of New Orleans, such as occurred during Hurricane Katrina, when flooding occurred as a result of these human interferences as well as poor land use decisions by the city of New Orleans to construct large numbers of residential units in known flood prone locations.

There are a number of record flooding events involving the Mississippi. The Great Mississippi Flood of 1927 occasioned levee and bank breaches is 145 locations, resulting in inundation of over 70,000 square kilometers of land area, with some flooding depths exceeding nine meters; the river attained a flood width of more than 97 kilometers just south of Memphis, Tennessee. This 1927 flood event is considered the most destructive riverine flood in recorded U.S. history.

The Great Mississippi Flood of 1951 was another event of widespread Mississippi flooding.

The Mississippi and Missouri River flooding in 1993 provided a further example of the power of the Mississippi Basin waters.

By comparison to these catastrophic and widespread flooding events, the localized effects attending Hurricane Katrina were small by juxtaposition.

Aquatic biota

Highfin carpsucker, endemic to the Mississippi. Source: Brian Zimmerman
There are at least 228 fish species present in the Mississippi River system. Demersal endemic species include the 50 centimeter (cm) highfin carpsucker (Carpiodes velifer), the 41 cmlake chubsucker (Erimyzon sucetta) and the nine cm spring cavefish (Forbesichthys agassizii).

Endemic benthopelagic fishes include the eight cm blackspotted topminnow (Fundulus olivaceus), the seven cmmud darter (Etheostoma asprigene) and the nine cm golden topminnow (Fundulus chrysotus).

Native pelagic-neritic fishPelagic-neritic fish are species found near a river mouth or sea edge. found in the Mississippi include the 61 cm skipjack shad (Alosa chrysochloris) and the 63 cm American gizzard shad (Dorosoma cepedianum).

Terrestrial ecoregions

Ecoregions along the Mississippi mainstem. Source: WWF
The chief ecoregions found in the Mississippi Basin along the mainstem are:
  1. Western Great Lakes forests
  2. Upper midwest forest-savanna transition
  3. Central forest-grasslands transition
  4. Central USA. hardwood forests
  5. Mississippi lowland forests
  6. Southeastern mixed forests

The Western Great Lakes forests has characteristic vegetation of a mixed forest that includes a Succession from quaking aspen (Populus tremuloides), paper birch (Betula papyrifera), and jack pine (Pinus banksiana) to white spruce (Picea glauca), black spruce (Picea mariana), and balsam fir (Abies balsamea). Common species of the northern hardwoods include sugar maple (Acer saccharum), red maple (Acer rubrum), American beech (Fagus grandifolia), hop hornbeam (Ostrya virginiana), basswood (Tilia americana), yellow birch (Betula alleghaniensis) and eastern hemlock (Tsuga canadensis).

The Upper midwest forest-savanna transition is a highly fragmented ecoregion, with few sizable intact habitat units. Amont the most significant intact units are the Baraboo Hills, Devils State Park (southern Wisconsin); Savanna River Depot, (sandy grasslands (Biome) and floodplain forests in northwestern Illinois); Upper Mississippi Wildlife Refuge (flood plain forests in eastern Wisconsin and western Minnesota); Mississippi Bluffs forests (relatively intact system in Minnesota); Richard J. Dorer State Forest (Minnesota); Whitewater Wildlife Management Area (Minnesota); Neceda National Wildlife Refuge (protected and managed wetlands); Horicon Marsh (southeastern Wisconsin stopover site for migratory geese); Kettle Moraine State Forest (southeastern Wisconsin).

The Central forest-grasslands transition has few remaining intact habitat elements; however, notable remaining intact units are: Goose Lake Prairies and Midewin National Grassland (northeastern Illinois); Palos Savanna (52.5 square kilometers of moderately fragmented savanna in northeastern Illinois) ; Kankakee Sands (a savanna-wet prairie that is the site of a restoration program along the Illinois-Indiana border); Osage Plains prairie fragments, an important Missouri site for the prairie chicken (Tympanuchus cupido), the richest and largest fragments of tallgrass prairie in this ecoregion; Cross Timbers area, an oaksavanna with tallgrass prairie understory (Arbuckle Uplift native grassland in southeastern Oklahoma); Indiana Dunes lakeshore grassland savanna (northern Indiana) and the Emiquon floodplain forest (western Illinois).

Central USA. hardwood forests is dominated by merely a few tree species. The oak-hickory forest becomes more akin to savanna in its northern elements. In southern Illinois and Indiana, the forest manifests a mosaic with prairie. Widepsread dominants are white oak (Quercus alba), red oak (Q. rubra), black oak (Q. velutina), bitternut hickory (Carya cordiformis), and shagbark hickory (C. ovata). Flowering dogwood (Cornus florida) often occurs in the understory, along with sassafras (Sassafras spp.) and hop hornbeam (Carpinus spp.). Intact moister sites exhibit American elm (Ulmus americana), tuliptree (Liriodendron tulipifera) and sweetgum (Liquidambar styraciflua).

Mississippi lowland forests feature baldcypress (Taxodium distichum) and water tupelo (Nyssa aquatica), which frequently codominate the canopy. Associated with river swamp forests are button-bush (Cephalanthus occidentalis), water ash (Fraxinus caroliniana), water-elm (Planera aquatica), and black willow (Salix nigra). Lower hardwood swamp forests are similar to river swamp forests, but have a more diverse woody community. Water hickory (Carya aquatica), red maple (Acer rubrum), green ash (Fraxinus pennsylvanica) and river birch (Betula nigra) increase in occurrence. Common herbs include butterweed (Senecio glabellus), jewelweed (Impatiens capensis), and royal fern (Osmunda regalis).

Southeastern mixed forests lie along the eastern side of the lower Mississippi. Pines were historically dominant, although hardwoods have been gaining dominance in the last several decades. Common pine species of this ecoregion include shortleaf pine (Pinus echinata), loblolly pine (Pinus taeda) and longleaf pine (Pinus palustris).Dominant understory plants include small trees like dogwood (Cornus spp.), redbud (Cercis canandensis), cedar (Juniperus spp.), and American holly (Ilex opaca). Abundant shrubs and herbaceous species include blackberry (Rubus spp.), sumac (Rhus spp.), honeysuckle (Lonicera spp.), and poison ivy (Toxicodendron radicans).
Mississippi River Basin showing soil organic carbon levels. Source: USGS

See also:


Monk's Mound, the largest of the Cahokia Mounds, Illinois. Source: Creative Commons
While hunter gatherers were present in the Mississippi Basin since the early Holocene, this watershed became one of the early centers of sedentary agriculture in North America, with evidence of systematic plant cultivation as early as the fourth millennium BC. Between 500 and 1400 AD a more advanced culture began to flourish in the basin, known as Mississippian; one of the most notable of the divisions of the MIssissippian culture was the Cahokian, whose advanced culture built great mounds and engaged in advanced art and complex societal practices.

A number of Native American tribes inhabited the Mississippi Basin, including the Ojibwe people, who called the rivermisi-ziibi, meaning great river. Besides the Ojibwe, other extant tribes in the basin include Cheyenne, Sioux, Potawatomi, Ho-Chunk, Fox, Kickapoo, Tamaroa, Quapaw and Chickasaw.

Important prehistory is contained in some of the sub-basins of the Mississippi. For example, since the early Holocene the lower Arkansas River valley was occupied by Paleo-Indians. Some of the iconic archaeological sites in this basin include the bluff dweller sites of the Ozark and Ouachita Mountains of extreme southwest Missouri and northwest Arkansas; other notable Native American sites are mound-building cites such as the Spiro site of eastern Oklahoma; these sophisticated mound-builders thrived in the era 800 to 1400 AD over most of the Arkansas and Oklahoma portions of the Arkansas River basin, and were known as the Caddoan Mississippian culture. Precursor civilizations to the Caddoan Mississippian culture in this region include the Fourche Maline culture that thrived from 200 BC to 800 AD.


Mississippi River scene at Vicksburg, 1855. Engraving in Ballou's Pictorial
Following the first European recording of the Mississippi by de Soto in 1541, Louis Jolliet and Jacques Marquette, representing France, were the next Europeans to forge into unexplored parts of the Mississippi Basin. In 1673 they employed a native Sioux guide, and found a new shortcut route (previously unknown to the French) that connected to Canada by way of the Illinois River. Jolliet was also the first to speculate on the value of a future canal that would eventually connect the Mississippi mainstem to the Great Lakes 75 years later.

After the Louisiana Purchase, The Mississippi and its tributaries became a chief mechanism for exploration of much of this vast new land acquisition coming into the USA. The Mississippi played a prominent role in the development of the western USA in the nineteenth century, and it grew thriving commercial ports along its extent.


  • S.Chaplin, A.Perera, S.Robinson, J.Adams, T.Gray, G.Whelan-Enns, K.Kavanagh, M.Sims, G.Mann. 2011. Western Great Lakes forests. World Wildlife Fund
  • Fishbase. 2010. Mississippi.
  • Richard A.Geyer. 1980. Marine Environmental Pollution: Dumping and mining. 574 pages Google eBook
  • Gregory F.McIsaac, Mark B.David, George Z.Gertner & Donald A.Goolsby. 2001. Eutrophication: Nitrate flux in the Mississippi River. Nature 414, 166-167
  • R.H.Meade and J.A.Moody. 1984. Causes for the decline of suspended-sediment discharge in the Mississippi River system, 1940–2007 Hydrology Processes, Volume 24
  • National Research Council (U.S.). Water Science and Technology Board. 2008. Mississippi river water quality and the Clean Water Act: progress. National Research Council Committee on the Mississippi River and the Clean Water Act. 239 pages Google eBook
  • Timothy R.Pauketat. 1998. Refiguring the Archaeology of Greater Cahokia. Journal of Archaeological Research Volume 6, Number 1
  • U.S.Army Corps of Engineers. 2007. Middle Mississippi River Regional Corridor: Collaborative Planning Study. Saint Louis, Missouri, USA: U.S. Army Corps of Engineers, St. Louis District.
  • A.Weakley, E.Dinerstein, R Snodgrass, K.Wolfe. 2011. Mississippi lowland forests. World Wildlife Fund


C. Michael Hogan, World Wildlife Fund (2014). Mississippi River. ed. Peter Saundry. Encyclopedia of Earth. NCSE. Washington DC. Retrieved from http://editors.eol.org/eoearth/wiki/Mississippi_River