I know you can see that any day at any time around Lake Erie...spent a bunch of time there, but was amazed how clean Lake Michigan and Lake Huron look, of course, I didn't take chemical analysis!
Pfft, if you think thats clean, gotta check out Lake Superior. Nows thats clean, can look down 20+ ft and see bottom in Huron bay. Going up there next weekend to hit the salmon run.
Lake Michigan has severly degraded in water quality in the past 20 years, I grew up fishing Lake Michigan and it sadens me to see how bad its gotten. Being an avid trout fisherman I take water quality EXTREMELY SERIOUSLY. If you wana see how bad Lake Michigan can be just go down to the port of Milwaukee, sumtimes its black as coal. After seeing the nite and day differance between the two, I know why there is a big movement to protect the great lakes.