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Great Lakes Watershed

intro-watershedNE Ohio Watershed Map
Click on each of the Great Lakes for more information from the
Great Lakes Information Network.
link to Great Lakes Information Network- Lake Superior
link to Great Lakes Information Network- Lake Michigan link to Great Lakes Information Network- Lake Huron link to Great Lakes Information Network- Lake Ontario
link to Great Lakes Information Network- Lake Erie
The Great Lakes are Superior, Michigan, Huron, Erie and Ontario. These lakes and their connecting channels form the largest fresh surface water system on earth.







courtesy of University of Wisconsin Sea Grant




Covering more than 94,000 square miles and draining more than twice as much land, these “freshwater seas” hold an estimated 6 quadrillion gallons of water. This is about 84 percent of North America’s freshwater and about 21 percent of the world’s supply. Only the polar ice caps contain more fresh water. If the water were spread evenly across all of the lower 48 states, the Great Lakes’ water would be about 9.5 feet deep.

Glaciers in the last ice age formed the Great Lakes about 10,000 years ago. The glaciers scooped out the land and as the glaciers receded, the large amount of melt water filled the depressions with water forming the Great Lakes. For more information see The Ice Age In Ohio (pdf)

The rivers and channels that connect the Great Lakes are an important part of the watershed system as they connect all of the lakes to the Atlantic Ocean.
 
 
The St. Marys River is the northernmost of these, a 60-mile waterway flowing from Lake Superior down to Lake Huron. At the St. Marys rapids, the Soo Locks bypass the rough waters, providing safe transport for ships. The St. Clair and Detroit rivers, and Lake St. Clair between them, form an 89-mile long channel connecting Lake Huron with Lake Erie.

The 35-mile Niagara River links lakes Erie and Ontario, and sends approximately 50,000 to 100,000 cubic feet of water per second over Niagara Falls; the man-made Welland Canal also links the two lakes, providing a navigational detour around the falls. From Lake Ontario, the water from the Great Lakes flows through the St. Lawrence River all the way to the Atlantic Ocean, about 1,000 miles away.
 



 


The Great Lakes Watershed includes part or all of eight U.S. states (Minnesota, Wisconsin, Illinois, Indiana, Michigan, Ohio, Pennsylvania and New York) and the Canadian province of Ontario. Today, more than 33 million people inhabit the Great Lakes Watershed: more than one-tenth of the population of the United States and one-quarter of the population of Canada.

In spite of their large size, the Great Lakes are sensitive to the effects of a wide range of pollutants. Major stresses on the lakes include toxic and nutrient pollution, invasive species and habitat loss. Sources of pollution include the runoff of soils and farm chemicals from agricultural lands, waste from cities, discharges from industrial areas and leachate from disposal sites.
 
The large surface area of the lakes also makes them vulnerable to direct atmospheric pollutants that fall as rain, snow, or dust on the lake surface, or exchange as gases with the lake water.

As a result of this deposition and other pollution, there are fish consumption advisories in the Great Lakes. Discharge flows from the Great Lakes are relatively small (less than 1 percent per year) in comparison with the total volume of water. Pollutants that enter the lakes are retained in the system and become more concentrated with time. For additional information, see the Great Lakes Atlas.
 
   
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