The Great Lakes and the Mississippi River basin are connected, but it's an artificial connection.
Around the turn of the last century canals and channels were dug that reversed the flow of water.
Waters that used to flow into Lake Michigan now flow into the Des Plaines River and eventually into the Mississippi.
The reversal was a way of separating Chicago's sewage from its drinking water supply.
And with more than 2 billion gallons of water a day flowing out of Lake Michigan, it's the largest diversion of Great Lakes water.
Undoing what was done around a hundred years ago has been considered crazy talk because of the expense involved, but some scientists are now embracing that idea.
In a new paper released in the Journal of Great Lakes Research, four lead scientists (Jerry Rasmussen, Henry Regier, Richard Sparks, and William Taylor) argue that the costs of permanent separation of the Great Lakes and Mississippi River Basin are worth it.