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 region depression in the upland area, independent of the overlap of Palaeozoic strata. The western half of the basin occupies a trough of synclinal structure. The Great Lakes are peculiar in receiving the drainage of but a small peripheral land area, enclosed by an ill-defined water-parting from the rivers that run to Hudson Bay or the Gulf of Saint Lawrence on the north and to the Gulf of Mexico on the south. The three lakes of the middle group stand at practically the same level: Lake Michigan and Lake Huron are connected by the Straits of Mackinac with the Mackinac Bridge