The Great Lakes are a series of five lakes located between the United States and Canada in north central North America. Together they are the largest group of fresh water lakes on Earth, making up 18% of total world supply.
The Great Lakes comprise:
- Lake Superior
- Lake Michigan - The only Great Lake located entirely in the United States.
- Lake Huron
- Lake Ontario
- Lake Erie
| Maximum depth
| Height above sea level
|Superior||31,700||2900||1332||600||2726||St. Marys River|
|Michigan||22,300||1180||925||577||1638||Straits of Mackinac|
|Huron||23,000||850||750||577||3827||Straits of Mackinac|
|Ontario||7,340||393||802||243||712||St. Lawrence River|
Although several other large lakes and islands make up part of the Great Lakes System. They drain through the Saint Lawrence River into the Gulf of Saint Lawrence. In 1959 the Saint Lawrence Seaway opened the Great Lakes to ocean-going boats, allowing travel well into the heart of North America. Although the Great Lakes themselves had been connected before this by a series of canals.
Since 1909 the United States and Canada have cooperated on the management and control of lake water with the International Joint Commission (IJC). At Niagara Falls, as much as 60% of the water is diverted for hydroelectric power generation for Ontario and New York State.
Because of the large size of the lakes many of the larger cities experience lake effect snow, where westerly winds capture moisture over the unfrozen lakes and when cooled over the land, heavy snows can fall. Additionally the lakes can moderate the warm temperatures in the summer, and release the heat in the fall.
Decline in Water Levels
-  The Great Lakes - An Environmental Atlas and Resource Book