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
Eastern Great Lakes and Hudson Lowlands (ecoregion) addition the World Wildlife Fund developed its own classification system, in which much of this region is called the Eastern Great Lakes lowland forests. Eastern Great Lakes and Hudson Lowlands (ecoregion) The Eastern Great Lakes and Hudson Lowlands region extends along the south shores of Lake Erie and Lake Ontario and the St. Lawrence River to Lake Champlain, and south down the Hudson River. It is primarily within the state of New York. In the north it meets the Mixedwood Plains Ecozone of Canada. It is mostly temperate deciduous forest and agricultural land. It is one of the 104 Level