Watersheds, Waterways, and Penguins: Part 4

The Concord River arises from the confluence of the Sudbury and Assabet Rivers in Concord and goes on to pour itself (as I said before) into the Merrimack. That's the sort of thing I like to know.

Looking further afield, the Ohio River arises from the confluence of the Allegheny and the Monongahela in Pittsburgh. Try saying this aloud: "the confluence of the Allegheny and the Monongahela". Say it a few times.

Of course, not every confluence involves three river names: far from it. Very often the outgoing stream bears the same name as one of the two incoming streams and the other is considered a tributary. (Is it still called a confluence in that case? Sometimes it is, certainly: that's how the city of Koblenz, where the Moselle flows into the Rhine, got its name.)

Sometimes the people who name the rivers get it wrong, in the sense that the bigger branch is called a tributary. A famous example is where the Missouri River meets the Mississippi at Saint Louis. The Mississippi upstream from Saint Louis is negligible in comparison with the Missouri. If anyone asks you what the longest river in North America is (and if they mean it to be a question about physical reality rather than about the names of things), the answer is not a river that has a single name for its whole length: it consists of the Missouri and part of the Mississippi. I believe this is widely known; I've known it since I was a child. (Actually--and I didn't know this until recently--there is more to say here. The Missouri arises from a confluence of not two but three rivers, not one of them called the Missouri, and the full list of names of segments of the continent's longest river seems to be "Mississippi River", "Missouri River", "Jefferson River", "Beaverhead River", "Red Rock River", "Hellroaring Creek".)

Anyway, by some kind of logic the upper portion of the Mississippi should have some other name, and the Missouri should be considered part of the Mississippi.

Don't get me wrong. I'm not here to complain, or to push one kind of logic at the expense of another. I can enjoy the names of rivers, and I can enjoy the reality of rivers, and I can also enjoy a little mismatch between the names and the reality.

After the Missouri the other main tributary of the Mississippi is the Ohio. This comes in further downstream, on the other side, the east. Imagine following the Ohio upstream from where it ends in the Mississippi at Cairo, Illinois. First you have Indiana on your left and Kentucky on your right. Later Ohio replaces Indiana, then West Virginia replaces Kentucky, then the river leads you into Pennsylvania and, as we know, ends (in name only) at Pittsburgh.

I like to think about the vast drainage basin of the Mississippi system, the huge middle portion of North America whose waters end up in the Mississippi Delta. You can see on a map that parts of it come very close to the Great Lakes. In Minnesota there is a divide, probably not very dramatic if you saw it up close, between the Mississippi and Lake Superior. It continues through Wisconsin and Illinois (where the relevant Great Lake is Lake Michigan) and into Indiana, possibly Michigan, and Ohio (now it's dividing the Ohio River from Lake Erie) and Pennsylvania, and even up into New York state, between Lake Ontario and the headwaters of the Allegheny.

The fairly vast drainage basin on the other side of this divide is that of the Saint Lawrence River, which is fed by the Great Lakes and opens into a wide bay or estuary called the Gulf of Saint Lawrence, in eastern Canada.

I have sometimes thought about the fact that there must be a point in New York where the basins of the Mississippi, the Saint Lawrence, and something else come together. I was pretty sure that the something else had to be Chesapeake Bay, because once, when I had occasion to drive from the Boston area to the State University of New York at Binghamton, somewhere on a lovely highway southwest of Albany, a sign told me that I was crossing the Susquehanna.

I like to imagine coloring in a map of North America in a certain way. First color the Mississippi basin. Then color the Saint Lawrence (or Great Lakes) basin. Look at the territory surrounded by these two basins and the Atlantic, and color in whatever drainage basin it is that touches both of the first two basins, namely that of Chesapeake Bay, which is fed by the Susquehanna, the Potomac, and some other rivers whose names I don't know. Now look at the remaining territory between the Saint Lawrence and Chesapeake basins and look for the basin that touches both; I suppose it is that of the Hudson. Now look between the Hudson and the Chesapeake and find the Delaware. Look between the Saint Lawrence and the Hudson and find, what? the Connecticut? And between the Saint Lawrence and the Connecticut the Merrimack? It's all about looking for those triple points. Between the Merrimack and the Connecticut is, I'm guessing, the Blackstone. And between the Blackstone and the Merrimack, finally the Charles?

Getting back to the Mississippi and the logic of river-naming, here's something I didn't know until recently, and it kind of blows my mind. Where the Ohio meets the Mississippi, the Ohio is in fact the bigger branch by flow rate (though not of course by length).

Imagine starting at the place in Louisiana where all that water flows into the Gulf of Mexico and, ignoring the names of things, going to see where the water is coming from. Travel up the stream, choosing at every confluence the branch that has the majority of the water. You would pass the mouths of the Red River, the Arkansas River*, and others, but at Cairo you would turn right and follow the Ohio. At Pittsburgh you would turn left and follow the Allegheny into western New York and then back into Pennsylvania, ending in some little creek in the woods.



* This is an impressively long river. And apparently outside of the state of Arkansas its name is pronounced with the stress on the second syllable. Think "Kansas". And apparently that's how some people used to pronounce the state of Arkansas, until the state legislature passed a resolution in 1881 to settle the matter.