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 is tied to what was left by melting glaciers when the lakes took their present form. Annually, only about 1% is "new" water originating from rivers, precipitation, and groundwater springs that drain into the lakes. Historically, evaporation has been balanced by drainage, making the level of the lakes constant. While the lake levels have been preserved, intensive human population growth only began in the region in the 20th century and continues today. At least two human water use activities have been identified as having the potential to affect the lakes' levels: diversion (the transfer of water to other watersheds) and