Does the Mississippi River really flow into the Ohio River?

[triplemultiplex]

The volume and size of the barge traffic on the Mississippi is fascinating. While Europe has some rivers with a large number of inland ships, they do not have the scale of the Mississippi and Ohio Rivers.

The U.S. is blessed with such a large natural transportation system, in the middle of the continent, serving a huge agricultural area with reliable output. It's one of the things in U.S. geography that really stands out if you think about it.

Yeah it's a pretty sweet set up.  The end result of having mountain building events on both margins of our continent separated by 170 million years.  Creates an enormous sedimentary basin in between all draining toward the same point.  The Appalachians were even kind enough to extend southwesterly enough so that the Tennessee River gets deflected back north and add even more water to the system.

Oh and shout out to the glaciers for making it so the Ohio above Portsmouth and the Mississippi above Prairie du Chien were added to the system.

[roadman65]

Also the dikes and levees for keeping the river from shifting or else who knows the location the outlet to the Gulf would be. 

Though the fact the first hundred miles of the river inland is on a long peninsula makes the river even longer as its mouth is really off shore. A barge going from NOLA to Biloxi has to make a long trip even though it's not that far. It's northeast of the Big Easy one has to south and then circle around.

[US 89]

The volume and size of the barge traffic on the Mississippi is fascinating. While Europe has some rivers with a large number of inland ships, they do not have the scale of the Mississippi and Ohio Rivers.

The U.S. is blessed with such a large natural transportation system, in the middle of the continent, serving a huge agricultural area with reliable output. It's one of the things in U.S. geography that really stands out if you think about it.

Yeah it's a pretty sweet set up.  The end result of having mountain building events on both margins of our continent separated by 170 million years.  Creates an enormous sedimentary basin in between all draining toward the same point.  The Appalachians were even kind enough to extend southwesterly enough so that the Tennessee River gets deflected back north and add even more water to the system.

Oh and shout out to the glaciers for making it so the Ohio above Portsmouth and the Mississippi above Prairie du Chien were added to the system.

The upper Tennessee draining north might be a more geologically recent change, though. If you look at those valleys around Chattanooga and a bit upstream, there sure is a nice broad valley that will take you directly to the Coosa River, which feeds into the Alabama and then to Mobile Bay. I'm not going to be able to find the link but there was something I was reading a while back that suggested this was probably the original drainage from eastern Tennessee.

[triplemultiplex]

The upper Tennessee draining north might be a more geologically recent change, though. If you look at those valleys around Chattanooga and a bit upstream, there sure is a nice broad valley that will take you directly to the Coosa River, which feeds into the Alabama and then to Mobile Bay. I'm not going to be able to find the link but there was something I was reading a while back that suggested this was probably the original drainage from eastern Tennessee.

The geologic history of all the "water gaps" in Appalachia is fascinating to me.

[CapeCodder]

The Ohio and Allegheny Rivers are considered the "Main Stem" of the Mississippi River from a hydrological and Strahler Number point of view.

[skluth]

I would look at this the other way.  The Mississippi River is the part that reaches the Gulf of Mexico.  The question is whether the Mississippi originates in the East or in the North.  You could say that the Minnesota River (following the main stem) joins the Missouri, which joins the Mississippi at Cairo.  I would propose (just to be contrarian) that the Mississippi starts in the Northwest and picks up the Minnesota and Ohio.

The Minnesota flows into the Mississippi just on the south side of Minneapolis/St Paul. It's headwaters are only a mile or two from the headwaters of the Red River of the North. Back in the glacial days of Lake Agassiz, the Minnesota River drained a lake larger than the current Great Lakes combined and is hugely responsible for the massive valley of the Mississippi from the Twin Cities south. (Glacial outflow also created the smaller St Croix, Wisconsin, Illinois, Wabash, and Scioto valleys, among others.) The average daily flow may be greater in the Ohio River at Cairo, but that's just an arbitrary definition. It could be distance from mouth to most distant headwater (Missouri-Jefferson branch). It could be defined like the Blue and White Nile, where the Mississippi would be called the Blue Mississippi north of Cairo, the Ohio the White Mississippi, and the Missouri the Brown Mississippi.

The US has a unique river geography. There are plenty of other rivers that have vast plains around them, but they all have problems. The Nile is easily navigable to Aswan and the prevailing winds will push sailboats upriver against the current, but it's unfortunately surrounded by desert. Mesopotamia has the same desert issue without the nice sail option. The Yangtze has most of its farmland in a region that is more like the Mississippi south of Cairo than the prairie to the north; it also has comparable flooding problems. The Amazon could be like the Mississippi if you chopped down all the rain forest but its land would not be as productive even though it's navigable to Peru. The Volga, Ob/Irtysh, Lena, and Mackenzie valleys might all be agriculture powerhouses one day should we get a recurrence of the Eocene thermal maximum, but that's a problem in the distant future. The closest is probably the Parana basin in South America which includes the Pampas and Chaco Plain, but that hasn't been nearly as exploited.

[kalvado]

The Ohio and Allegheny Rivers are considered the "Main Stem" of the Mississippi River from a hydrological and Strahler Number point of view.

Are you sure about Strahler number? The only one I can find shows 9th order Ohio flowing into 10th order Mississippi:
http://www.horizon-systems.com/NHDPlusData/NHDPlusV1/NHDPlusExtensions/SOSC/SOSC_technical_paper.pdf

[CapeCodder]

The Ohio and Allegheny Rivers are considered the "Main Stem" of the Mississippi River from a hydrological and Strahler Number point of view.

Are you sure about Strahler number? The only one I can find shows 9th order Ohio flowing into 10th order Mississippi:
http://www.horizon-systems.com/NHDPlusData/NHDPlusV1/NHDPlusExtensions/SOSC/SOSC_technical_paper.pdf

I stand corrected.