Great Lakes form a single, naturally interconnected body of fresh water, within the Great Lakes Basin. They form a chain connecting the east-central interior of North America to the Atlantic Ocean. From the interior to the outlet at the Saint Lawrence River, water flows from Superior to Huron and Michigan, southward to Erie, and finally northward to Lake Ontario. The lakes drain a large watershed via many rivers, and are studded with approximately 35,000 islands. There are also several thousand smaller lakes, often called "inland lakes," within the basin. The surface area of the five primary lakes combined is roughly equal to
Great Lakes Waterway Great Lakes Waterway The Great Lakes Waterway is a system of natural channels and canals which enable navigation between the North American Great Lakes. Though all of the lakes are naturally connected as a chain, water travel between the lakes was impeded for centuries by obstacles such as Niagara Falls and the rapids of the St. Marys River. Its principal civil engineering works are the Welland Canal between Lakes Ontario and Erie, and the huge Soo Locks between Huron and Superior. Dredged channels were constructed in the St. Marys River, the Detroit River, Lake St. Clair and the St. Clair