How Chicago reversed a river (and messed up the environment)

In 1900, Chicago achieved an ambitious goal: reversing the Chicago River so that it stopped flowing into Lake Michigan. The idea was to keep their sewers from polluting Lake Michigan (and therefore their water supply), as CityLab explains. The city accomplished this by building the Chicago Sanitary and Ship Canal, which connects the Chicago River and the Des Plaines River, which connect Lake Michigan to the Mississippi River. Altogether, this new system stopped the Chicago River from dumping into Lake Michigan by reversing its exit into the lake and having it instead connect to Des Plaines River. The project worked, stopping water-born illness among city residents. All this sounds like an impressive feat, but today it's causing new problems, as the Milwaukee Journal Sentinel reported in 2010. The biggest one is invasive species, particularly the Asian Carp. The Chicago Sanitary and Ship Canal means those fish can get from the Mississippi to the Chicago River and then into Lake Michigan. These massive, leaping, invasive fish can not only disrupt ecosystems and also pose a threat to boaters. It's not just Asian carp, either; invasive fish have proven capable of getting past an electric barrier constructed to keep them out. To solve the problem, the Army Corps of Engineers earlier this year released eight proposals to keep fish out of the lake, including the possibility of reconstructing the former natural barrier.