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<br />
<br />The Great Lakes
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<br />General Background . .-
<br />The Great Lakes Drainage Basin consists of the five Great Lakes (Superior, Michigan, Huron, Erie, and:..,
<br />Ontario), their connecting channels (St. Mary's River, St. Clair River-Lake St. Clair-Detroit River,and::'.\f
<br />the Niagara River- Welland Canal), the St. Lawrence River up to Trois Rivieres and tributary surface and':~
<br />groundwater sources from the land that drains into the Lakes. The Basin covers portions of Minnesota..-;:,:;~;J.
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<br />Wisconsin, Illinois, Indiana, Michigan, Ohio, Pennsylvania, New York, Ontario, and Quebec. The Basin .,~:{~f~
<br />covers nearly 300,000 square miles, wit~ the Lakes themselves accounting for approximately one third o(":~~;~~
<br />that area, and the drainage basin the remaining two thirds. Roughly 33 million people live in the Basin,J/t"i'
<br />25 million in the United States and the remainder in Canada. As a whole, the Great Lakes contam:l,
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<br />roughly 18% of the world's and 95% of the United States' fresh surface waters, and possess over 11,200\
<br />miles of shoreline. ' . . .
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<br />The flow of water from Lake Superior to the Atlantic occurs very slowly. A single drop of water
<br />deposited in Lake Superior on average takes over 300 years to reach the Atlantic (retention time). This
<br />relatively prolonged hydrologic process means that the Great Lak~s require a significant amount of time
<br />to process changes in water quality and quantity. In addition, the large surface area of the lakes, covering
<br />94,000 square miles, makes the Lakes vulnerable to direct atmospheric pollutants that fall with rain or '
<br />snow and as dust on the water surface. The Great Lakes also include sensitive interstitiaVtidal and,
<br />wetl~ds areas. Thus, despite the large quantity of water in the Basin, the Great Lakes system is very
<br />fragile and extrernely vulnerable to environmental changes.
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<br />The Great Lakes' support numerous species of animals, more than 20 species of reptiles, over 100 species
<br />of birds, 'and over 100 species of fish, including rare, endangered, and threatened species such as the
<br />eastern fox snake', bald eagle, spotted turtle, fowler's toad, and Lake Erie water snake. Toxic
<br />contaminants include persistent organic chemicals and metals, which enter' the lake through both point
<br />sources such as industrial waste effluent or sewage discharge and non-point sources such as diffuse land
<br />runoff from agriculture and waste sites and from atmospheric deposition (i.e. acid rain). Other ,nutrients
<br />such as nitrogen and phosphorous from agricultural pesticide runoff pollute the ecosystem by promoting
<br />eutrophication, the accelerated production of certain organisms such as algae that deplete oxygen supplies
<br />for other species. The introduction of non-native species has had a trernendous impact on the Great Lakes.
<br />The most widely known example is the exponential and destructive growth of the Zebra Mussel. Some
<br />species have been introduced deliberately (i.e. the steelhead, chinook, and coho salmon), others of have
<br />been carried in the ballast water of commercial navigation vessels, and others have migrated in through
<br />man-made diversion projects.
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<br />Roughly 4,500 c.f.s. of water within the Great Lake Basin is withdrawn for consumptive purposes.
<br />Hydroelectric energy requires the withdrawal of almost 50,000 c.f.s. of water from the Great Lakes and
<br />accounts for the single largest source of water withdrawals (both consumptive and non-consumptive) in
<br />the Basin. The Great Lakes provide an important commerCial navigation route from the, central area of
<br />North America to the Atlantic. More than 200 million tons of iron ore, coal, limestone, and grain are
<br />shipped each year, accounting for 85% of the system.'s commerce. Recreation and tourism also account
<br />for a significant portion of the economic activity of the Great Lakes Basin, generating almost $12 billion
<br />in economic activity annually. More than 20 percent of the Great Lakes shoreline has been developed as
<br />residential property. Commercial fisheries catch roughly 50,000 tons of fish per year valued at around $1
<br />billion.
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<br />Water levels in each of the Great Lakes naturally rise and fall according to the amount of water entering
<br />the lake. Human activities also affect lake levels. Given the limited natural outflows of the Great Lakes,
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