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 to apply for additional federal research and education funds allocated to these national resources. Following a small uproar, the Senate voted to revoke the designation on March 24 (although New York and Vermont universities would continue to receive funds to monitor and study the lake). In the early years of the 21st century, water levels in the Great Lakes were a concern. Researchers at the Mowat Centre said that low levels could cost $19bn by 2050. Except when the water is frozen during winter, more than 100 lake freighters operate continuously on the Great Lakes, which remain a major water