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Re: Illinois drainage
From: Frank Reed CT
Date: 2005 Nov 22, 01:56 EST
From: Frank Reed CT
Date: 2005 Nov 22, 01:56 EST
George H asked: "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?" The Chicago River famously was reversed in 1900. The ridge that separates the Chicago drainage from the rest of Illinois was supposedly only about eight feet high in places, but it's dense clay and rock so there would not have been significant natural seepage. Building foundations in Chicago routinely go well below lake level. Did you hear about the "Great Chicago Flood" in 1992? There's plenty of info on the reversal of the Chicago River on the web, so I'll just point you to a google search that works well: http://www.google.com/search?as_q=chicago+river&as_oq=reversed+reversal The top results, from the Chicago Public Library, are particularly good. It is true that, today, the waters of Lake Michigan flow both east towards the St. Lawrence and southwest towards the Mississippi. The flow southwest is not very great though. -FER 42.0N 87.7W, or 41.4N 72.1W. www.HistoricalAtlas.com/lunars