My theory: Just like climate change, the levels of all lakes are cyclical. I recalled Lake Michigan being at a low level several years ago so I searched for historic data. First, Lake Superior is currently 2" higher than they recorded back in 1926 and all the other lakes are several inches above their low level records.

See: http://www.lre.usace.army.mil/greatlakes...keswaterlevels/

With cyclical climate, we are always in either a warming trend or a cooling trend. Which ever we are in would be exploited.