If we're going to talk about the quality of river water then we should let Mark Twain have his say (from Life on the Mississippi):

"...and then they got to talking about differences betwixt ...clear-water rivers and muddy-water ones. The man they called Ed said the muddy Mississippi water was wholesomer to drink than the clear water of the Ohio; he said if you let a pint of this yaller Mississippi water settle, you would have about a half to three- quarters of an inch of mud in the bottom, according to the stage of the river, and then it warn't no better than Ohio water - what you wanted to do was to keep it stirred up - and when the river was low, keep mud on hand to put in and thicken the water up the way it ought to be.

The Child of Calamity said that was so; he said there was nutritiousness in the mud, and a man that drunk Mississippi water could grow corn in his stomach if he wanted to. He says:

"You look at the graveyards; that tells the tale. Trees won't grow worth shucks in a Cincinnati graveyard, but in a Sent Louis graveyard they grow upwards of eight hundred foot high. It's all on account of the water the people drunk before they laid up. A Cincinnati corpse don't richen a soil any."

And they talked about how Ohio water didn't like to mix with Mississippi water. Ed said if you take the Mississippi on a rise when the Ohio is low, you'll find a wide band of clear water all the way down the east side of the Mississippi for a hundred mile or more, and the minute you get out a quarter of a mile from shore and pass the line, it is all thick and yaller the rest of the way across."