Great Lakes Areas of Concern rivers, and oceans causing pollution and buildup of sediment. Nonpoint source pollution is said to be the most problematic and hardest to reverse of the types of pollution because it is so hard to regulate and pinpoint where it originates. Many experts agree that nonpoint source pollution is the biggest concern facing the Great Lakes. With the increase of urbanization, a toll has been taken on the lakes in these areas. Lakes that once had stable ecosystems with the appropriate amount of plant life are now full of massive amounts of plants and algae that have been fed by excess
Great Lakes flooding. Running cut logs down the tributary rivers into the Great Lakes also dislocated sediments. In 1884, the New York Fish Commission determined that the dumping of sawmill waste (chips and sawdust) had impacted fish populations. The first U.S. Clean Water Act, passed by a Congressional override after being vetoed by US President Richard Nixon in 1972, was a key piece of legislation, along with the bi-national Great Lakes Water Quality Agreement signed by Canada and the U.S. A variety of steps taken to process industrial and municipal pollution discharges into the system greatly improved water quality by the 1980s,