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Coldwater bacteria threatens Great Lakes salmon
Charlevoix Courier (5/3)
A new study shows a bacterial disease that sickens fish whether raised in captivity or in the wild is imperiling popular salmon species in the Great Lakes Basin.

Central Michigan University opens interactive Great Lakes exhibit
WWTV-TV - Cadillac, MI (4/19)
The Great Lakes are the shining jewel of Michigan. And now there's a kid-friendly exhibit featuring the beautiful bodies of water.

60,000 trees and counting
Erie Times-News (4/17)
Sixty thousand and counting. That's how many trees and shrubs have been planted by Crawford County students in 16 years, in environmental projects sponsored by the Crawford County Conservation District and Pennsylvania state Bureau of Forestry.

Presque Isle an academic draw for Gannon students
Erie Times-News (4/10)
In Pennsylvania, Presque Isle State Park has long been a draw for tourists looking for the perfect place to swim and sunbathe. But the park, Presque Isle Bay and Lake Erie are also a draw for another group: science-minded students and their teachers.

TEACH Calendar of Events
What's going on in your neighborhood this month? Meet other people and learn together at recreational and educational events! Our new dynamic calendar is updated daily with current educational events.
Water levels on the Great Lakes

table of contents
Introduction
Three types of water level fluctuations
History repeating itself: Hydrographs illustrate historical levels
How levels and flows are measured
Effects of lake level fluctuations
References and more information

Water levels on the Great Lakes

Click to see larger image. Water levels are part of the ebb and flow of nature.

The difference between the amount of water coming into a lake and the amount going out is the determining factor in whether the water level will rise, fall or remain stable. When several months of above-average precipitation occur with cooler, cloudy conditions that cause less evaporation, the levels gradually rise. Likewise, prolonged periods of lower-than-average precipitation and warmer temperatures typically result in lowering of water levels.

The recent decline of Great Lakes' water levels, now at lows not seen since the mid-1960s, is due mostly to evaporation during the warmer-than-usual temperatures of the past three years, a series of mild winters, and below-average snowpack in the Lake Superior basin.

Because the major factors affecting the water supply to the lakes--precipitation, evaporation and runoff--cannot be controlled or accurately predicted for more than a few weeks into the future, the influence of man-made regulation of lake levels is very limited. Nature has most of the control, adding water through snow and rain, and taking it away through evaporation.

Graphic: Lake Superior's south shore, April 2000.

Detailed Map: The Great Lakes-St. Lawrence River system


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