six quadrillion gallons http://www.great-lakes.net/lakes/ref/lakefact.html http://www.great-lakes.net/lakes/ref/lakefact.html 20 percent of the world’s surface fresh water http://www.great-lakes.net/lakes/ref/lakefact.html http://www.great-lakes.net/lakes/ref/lakefact.html http://www.great-lakes.net/lakes/ref/lakefact.html http://www.great-lakes.net/lakes/ref/lakefact.html http://www.great-lakes.net/lakes/ref/lakefact.html http://www.great-lakes.net/lakes/ref/lakefact.html http://www.great-lakes.net/lakes/ref/lakefact.html Information about the Great Lakes http://www.great-lakes.net/lakes/ref/lakefact.html Great Lakes Information Network Facts http://www.great-lakes.net/lakes/ref/lakefact.html circumference http://www.great-lakes.net/lakes/ref/lakefact.html http://www.great-lakes.net/lakes/ref/lakefact.html http://www.great-lakes.net/lakes/ref/lakefact.html 95 percent of the United States’ fresh water supply