Lake Level Research on the Great Lakes

Lake Level Research on the Great Lakes (HM2LOY)

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N 45° 47.009', W 84° 43.387'

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Mackinaw City Historical Pathway

Researchers coming and going from Mackinaw City's marina are discovering that evaporation from the Great Lakes, a key factor in the level of the lakes, is far more complicated than formerly thought. An understanding is important for commerce, policy makers and environmentalists.

What determines the level of the lakes? In the short term, precipitation and runoff bring water into the lakes. Evaporation and drainage, both natural and man-made, take water out.

Evaporation is the least understood of all of these and is the focus of studies at two nearby lighthouses, chosen as research sites because they sit in the middle of the lakes, tall and unobstructed.

Evaporation accounts for 40% of the water lost by the lakes; natural drainage accounts for most of the remaining 60%.

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    November matters the most

Just one very cold windy spell in November can result in 1/2 inch of water level drop in all of the Great Lakes. The evaporation takes away water and heat from the lakes and will cause ice to form earlier, cutting off the November, December, January evaporation. As ice then builds, it delays the spring thaw, slowing April and May evaporation.

The feedback cycle is very complex and requires long-term study.


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Sophisticated equipment is mounted on White Shoal and Spectacle Reef lighthouses to collect the data for Lake Michigan and Lake Huron.

Data is collected on wind speed, humidity, ice cover (when little or no evaporation occurs), and temperature differentials between the air and water.

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Information compliments of:
Dr. Peter D. Blanken, Professor
Department of Geography
University of Colorado at Boulder
Marker ConditionNo reports yet
Date Added Thursday, October 10th, 2019 at 8:01am PDT -07:00
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Locationbig map
UTM (WGS84 Datum)16T E 676989 N 5072512
Decimal Degrees45.78348333, -84.72311667
Degrees and Decimal MinutesN 45° 47.009', W 84° 43.387'
Degrees, Minutes and Seconds45° 47' 0.54000000000002" N, 84° 43' 23.22" W
Driving DirectionsGoogle Maps
Which side of the road?Marker is on the right when traveling North
Closest Postal AddressAt or near , ,
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