The Great Lakes were formed by the retreat of the mile-thick glaciers of the Wisconsin Ice Age between 10,000 and 7,000 years ago. The watershed is an irreplaceable international treasure. The watershed includes eight States and a Canadian Province. The Great Lakes hold about 6 quadrillion gallons of water, or about 95% of the United States’ fresh surface water and 20 percent of all the fresh surface water in the world. If the water in the Great Lakes was spread evenly over the continental U.S., it would cover the land with about 10 feet of water! From East to West, the Great Lakes stretch for nearly a thousand miles across the heartland of the United States and Canada. The watershed drains almost 200,000 square miles. Dubbed “the nation’s fourth seacoast”, the U.S. Great Lakes shoreline is over 4,500 miles long, longer than the U.S. East and Gulf coasts combined. The total Great Lakes shoreline is over 10,000 miles long, including 35,000 islands. The Great Lakes watershed is so large that it is one of the most identifiable features of North America when viewed from space.
The northern part of the Great Lakes watershed is primarily forested, while the southern part is primarily agricultural land.
The Great Lakes watershed is home to over 40 million people. Over 25 million people in the U.S. rely on the Lakes for their drinking water. The watershed contains 20% of all U.S. timberland and 20% of all U.S. manufacturing (58% of cars made in the U.S. and Canada are made in the basin). The Lakes support a $1 billion-plus recreational fishing industry.
Major U.S. cities in the Great Lakes watershed include Buffalo, New York; Erie, Pennsylvania; Cleveland, Ohio; Detroit, Saginaw, and Grand Rapids Michigan; Chicago, Illinois; Milwaukee, Green Bay and Superior, Wisconsin; and Duluth, Minnesota.
Natural Habitats in the Great Lakes watershed include: wetlands, sand dunes, islands, and alvars. Some of these are unique in all the world. There are an estimated 300,000 acres of Great Lakes basin coastal wetlands. Great Lakes sand dunes, which occur on all five lakes, comprise the largest collection of freshwater coastal dunes in the world. Great Lakes islands comprise the world's largest freshwater island system. There are about 35,000 Great Lakes islands. Manitoulin Island in northern Lake Huron is the world's largest freshwater island. Great Lakes alvars are naturally open areas of thin soil over limestone or marble bedrock which host a distinctive vegetation community. The Great Lakes contain 95% of the world's alvars. Alvars are home to hardy, globally rare plant and animal species - some of the stunted conifer trees are estimated to be 400 to 500 years old.
The presence of contaminants, pathogens, invasive species, and the loss of habitat threaten the health of the Great Lakes ecosystem: Every one of the lakes has multiple fish consumption advisories due to toxic chemical contamination. The major pathways for many of these persistent toxics are contaminated sediments and air deposition from nearby and even global sources. Too many Great Lakes beaches are periodically closed due to pollution resulting from storm events and overflows and leaks from out-dated sewage systems. The introductions of non-native, invasive species into the Great Lakes severely disrupt the functioning of the food webs, and that can have very large economic impacts. Over 160 non-native species have already been introduced in the Great Lakes ecosystem. The cost of dealing with invasive species nationally has been estimated at more than $100 billion annually. The zebra mussel is a good example of how problems in the Great Lakes affect the nation: from their introduction in the Detroit River in 1988, they have now spread to the entire Mississippi River basin and from Oklahoma to Connecticut. The continued loss of habitat due to urbanization and urban sprawl threaten the healthy functioning of plants, animals, and, ultimately, humans.
USEPA Great Lakes National Program Office
Great Lakes Binational Programs
Visualizing the Great Lakes, online image collection
International Joint Commission
Council of Great Lakes Governors
Great Lakes Fishery Commission
Great Lakes Research Consortium
National Wildlife Federation Great Lakes Office
Council of Great Lakes Industries
Gary Gulezian, Director, USEPA Great Lakes National Program Office
(312) 886 - 5870
Anthony Kizlauskas, Communications and Outreach Team Leader, USEPAGreat Lakes National Program Office
(312) 353 - 8773