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George,

This isn't much help, but I recall that the flow of the Chicago River
was reversed when they built the Chicago Ship and Sanitary Canal.  I
am quite sure that originally the Chicago River flowed into Lake
Michigan, but not now, if my memory of the flow reversal is correct.
Thus, formerly, there was no chance for the torrent you envision from
erosion.  However, I believe by the time the book was written, the
flow would have been reversed, and thus the statement that the water
was from Lake Michigan was correct, at least in part, since some or
most of the water in the Illinois River would come from it's native
watershed, not from the Chicago River.

It's pretty flat there, so these flows would be fairly gentle, at
least over centuries.

Fred


On Nov 21, 2005, at 6:09 AM, George Huxtable wrote:

> To be honest, this isn't really a question about navigation, but about
> geography and hydraulics. But some Nav-l contributors hail from the
> Illinois
> area, so perhaps know the answer.
>
> I've been reading an odd book, published in 1911, The Log of the
> "Easy Way".
> This is about the voyage of a young couple, in 1900-01, in a house-
> boat or
> "shanty-boat", drifting down the Mississippee to New Orleans. The
> journey
> started in Chicago, with a tow through the "Old Canal", which
> presumably was
> later enlarged into the present Ship Canal. Then down the Illinois
> River to
> the Miss.
>
> The book took my interest as it took in the same stretch of the Miss.,
> between St Louis and Cairo, as had been used by Lewis and Clark, a
> century
> before, to reach their official setoff point.
>
> I'm aware of (and have always been rather puzzled by) how close the
> drainage
> of the Miss. basin comes to the Great Lakes, West of Chicago, but have
> presumed there's a narrow watershed, close West and South of Lake
> Michigan,
> which prevents that lake from spilling over to end up at New Orleans.
>
> And yet, in this book, the author, having reached the Illinois River,
> comments after passing La Salle / Peru, that "Its water may come
> from the
> cold, clear depths of Lake Michigan but ... ".  Surely not, I
> surmise. If
> that had ever been the case, the watercourse would have eroded over
> the
> millennia to become, by now, a torrent. Is it even hydraulically
> possible,
> even if the ground West of Lake Michigan is permeable to
> underground flow?
> That would require the water level in the upper Illinois to be
> lower, with
> respect to sea-level, than is Lake Michigan, at 580 feet? Is that
> the case?
>
> Presumably, there's a dividing line somewhere, on one side of
> which, if you
> pee on the ground, it will end up in the St. Lawrence, and on the
> other
> side, in the Gulf of Mexico. How far do you have to travel from Lake
> Michigan, to reach that line? It's not an important matter, but it
> interests
> me.
>
> George.

   

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