Six quadrillion gallons of fresh water; one-fifth of the world’s fresh surface water (only the polar ice caps and Lake Baikal in Siberia contain more); 95% of the U.S. supply; 84% of the surface water supply in North America. Spread evenly across the continental U.S., the Great Lakes would submerge the country under about 9.5 feet of water.
More than 94,000 square miles/244,000 square kilometers of water (larger than the states of New York, New Jersey, Connecticut, Rhode Island, Massachusetts, Vermont, and New Hampshire combined, or about 23% of the province of Ontario). About 295,000 square miles/767,000 square kilometers in the watershed (the area where all the rivers and streams drain into the lakes).
United States and Canada — 10,900 miles/17,549 kilometers (including connecting channels, mainland and islands). The Great Lakes shoreline is equal to almost 44% of the circumference of the earth, and Michigan’s Great Lakes coast totals 3,288 miles/5,294 kilometers, more coastline than any state but Alaska.
References: Great Lakes Basin brochure, 1990, Michigan Sea Grant
Lake Erie information: http://great-lakes.net/conditions/erie.html
Lake Huron information: http://great-lakes.net/lakes/huron.html
Lake Michigan information: http://great-lakes.net/lakes/michigan.html
Lake Ontario information: http://great-lakes.net/lakes/michigan.html
Lake Superior information: http://great-lakes.net/lakes/superior.html
Also, Lake St. Clair: http://great-lakes.net/lakes/stclair.html