posted
So, this random question popped in my head, that I didn't think should have been hard to answer. I could see a 7 or 8 year old asking this when they learn about the water cycle and the continental divide.
The question is this: Once you are East of the North American Continental Divide, how do you know, whether a drop of water will end up in the Great Lakes, the plain old Atlantic, or the Gulf of Mexico?
Turns out its more complicated than I thought. I pestered two of my favorite civil engineers and managed to get some answers, but I still haven't got it completely figured out.
Everything in the Mississippi River Basin drains into the Gulf of Mexico. Logic says that everything North of the geographic location of the basin shown on that map probably goes into the Great Lakes, though the stuff in Minnesota could concievably drain into the Great Slave Lake in Canada. There are two points at which the Mississipi River Basin actually touches one of the Great Lakes. This happens at the bottom of Lake Michigan, where the Chicago River has been reversed and now flows to the Mississipi, out of the Lake, and at the Ohio River where there is a lock and dam system connecting it to Lake Erie.
There was a subcontinental divide that was twelve miles away from Lake Michigan which determined whether the water went to the Lake or to the Mississipi (I actually work fairly close to it.) But they hacked through that the ridge since it was only 8 feet high, when they changed the direction of the flow of the Chicago River, to help Chicago's sanitation at the time.
So that basically takes care of the area closest to me, and the entire Missisipi River Basin. Most of Texas, probably drains to the Rio Grande, and out the Gulf that way. I'm guessing Alabama and Florida's panhandle drain to the gulf. But a state like Georgia, could go either way. I'm sure the Appalacians form part of another natural subcontinental divide, but wonder exactly where that line runs.
And now, I've started wondering about, south America and Eurasia, as to where their subcontinental divides are. In Europe they've got rivers that flow both north emptying into the north Atlantic, and South into the Mediterranian.
Yeah, I think too much, but other heads might have other ideas on the subject too. So if you get any ideas let me know.
posted
I guess this is one of those phenomena that I figure will go on happening whether or not I think about it. I'm pretty sure that while we are west of the Continental divide, everything in our immediate locality goes to the Great Salt Lake.
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posted
AJ, this is a very annoying post, because it's so interesting that I can't stop thinking about it, but I have no means of getting a clear answer.
The danger of hanging out with interesting folk, I guess.
posted
I want to live briefly inside AJ's head, just for a bit. It must be very hot. It is always going and going and going. Posts: 2919 | Registered: Aug 2004
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posted
Grin, Sara, to add another twist, your husband told me over on Grenme, where I cross-posted this that there is a river with origins in Minnesota, that ends up in the Arctic Ocean. That would really screw with small children learning about the continental divide if they learned that.
And there are some interesting exceptions like the Snake River too, which actually empties to the Pacific despite being on the "wrong" side of the line.
posted
AJ - There are two contenental divides -- East/West and North/South. If there was only one, the Mississippi would flow to the Atlantic, no? The Red River just happens to be on the other side of the North/South divide, and so flows North. We learned about both in elementary school... perhaps because the North/South one runs through our state.
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posted
Woo hoo! Here's info on the Eastern Continental Divide in Georgia. It discusses the Florida issue too. I'm not the only nut case out there. This guy definitely did more work than I did. http://www.gpsinformation.org/jack/Divide/Divide.html
Yes, that link above is a gold mine! If you scroll down a ways there is map with all of the divides on it!!!
quote: Triple Points: A triple point, or triple divide, is the place where two continental divides intersect and water drains into three different watersheds. Five widely-recognized triple divides exist in the United States, including: Triple Divide Peak, Montana, The Hill of Three Waters, Minnesota, Three Waters Mountain, Wyoming, an unnamed hilltop near Gold, Pennsylvania, and the unofficially named Headwaters Hill, Colorado.
posted
Actually, the computer modeling dude over at AmericanScientist wrote an excellent program designed to find the continental divide by gradually flooding the Earth, and marking each point at which the (blue)Atlantic waters met the (green) Pacific waters as the water level increased.
An interesting sidebar is that the US EastCoast becomes an island (or a near island with a very narrow pennisula south of LakeMichigan and LakeSuperior joining the East to the West) as the ocean level increases to match that which would be produced by a total meltdown of Earth's icecaps. Unfortunately, I think they removed the program from the site. So ya can't start&stop the flooding like ya useta.
posted
NOAA is a great resource, too. I want to say that the Mississipi River Basin actually extends up into Canada, too, and there is a big consortium studying it through NOAA, but I'll have to get on my lapto for a link. Edit-- Drat, its just on my work computer, sorry.
posted
Hmmm, AJ, I even found that link when we were talking about this last night, but didn't bother to look toward the bottom of the page so I thought it was specific to GA only. Oh, well, glad you found it too.
Posts: 609 | Registered: Apr 2003
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posted
I emailed the dude that made the Georgia page, and told him thank you. He said he was actually taking Rapid Transit down the eastern continental divide and didn't know it. His thing, and the main gist of his site is everything you ever needed to know about GPS. This was just a diversion he was curious abou too.
AJ
(oh and sara, your new screen name vastly amused me!)
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