Are the Great Lakes filled with brackish water or freshwater?

The great lakes are fresh water and flow to the Atlantic ocean by the Saint Lawrence River, lake Superior is the highest lake is at a elevation of Approx. 600 ft above sea level. read more

The Great Lakes are the largest group of freshwater lakes on Earth by total area, and second largest by total volume, containing 21% of the world's surface fresh water by volume. The total surface is 94,250 square miles (244,106 km 2), and the total volume (measured at the low water datum) is 5,439 cubic miles (22,671 km 3), slightly less than the volume of Lake Baikal (23,615 km³). read more