A century back, the reversal of the Chicago River to send off the city's waste to the Mississippi River instead of it flowing into Lake Michigan, was cheered as an engineering marvel, but things seem to have potentially changed now.

Michigan is suing Illinois to try and re-reverse the river in order to keep the "voracious, invasive Asian carp" from flowing into the lake. The suit is being moved to the Supreme Court, and also challenges Chicago's much controversial withdrawal of up-to 2 billion gallons of water almost every day from Lake Michigan.

For very long, environmental groups have been calling for the ecological separation of the "Great Lakes from the Mississippi River basin to curb the spread of invasive species and to retain Great Lakes water in the Great Lakes basin". Chicago diversion has pulled down lakes Michigan and Huron by an estimated 3 inches.

According to environmentalists and policy-makers, if the Asian crap flows into the Great Lakes, it could end up wiping out "plankton that makes up the base of the food chain, severely impacting fishing and lake-based tourism".

"It's a matter of self-defense economically and ecologically for Michigan", said Michigan Attorney General Mike Cox.