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'Once in a lifetime ' experience: Lighthouse keeper on Lake Superior
CBC News (5/19)
A group is hiring two students to serve as lighthouse keepers this summer on Porphyry Island, about 40 kilometers east of Thunder Bay, Ont.

Superior students set sail for hands-on learning about St. Louis River, Lake Superior
Wisconsin Public Radio (5/16)
Close to 1,500 students from northern Minnesota and Wisconsin set sail for a day on St. Louis River to learn about the Great Lakes, as part of the week-long St. Louis River Quest.

Tree group aims to ‘ReLeaf’ Michigan
WKAR - East Lansing, MI (5/10)
An Ann Arbor-based organization has been planting trees all over Michigan since 1988. ReLeaf Michigan helps property owners learn about trees and how to plant them, citing their numerous benefits.

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.

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

4 | How levels and flows are measured

Water levels are measured and recorded at many locations around the Great Lakes and on their connecting channels.

Click to see larger image.The National Ocean Service of the National Oceanic and Atmospheric Administration (NOAA) presently operates 31 water level gages on the Great Lakes and 18 gages on the connecting channels. In Canada, the Canadian Hydrographic Service maintains 29 water level gages on the Great Lakes and 27 on the St. Lawrence River. Other agencies, including the U.S. Army Corps of Engineers, New York Power Authority and Ontario Power Generation, also operate recording gages at various locations on the lakes.

See also: Map of Great Lakes Water Level Gauging Stations

Great Lakes water levels are officially measured from the International Great Lakes Datum 1985 (IGLD 1985). This datum is referenced to sea level, as measured at Rimouski, Quebec, near the mouth of the St. Lawrence River. Because the crust of the earth in the Great Lakes region is continuously rising with respect to sea level, and the rate of movement is not uniform throughout the region, the IGLD must be updated every 25 to 30 years.

See also: FAQ about the International Great Lakes Datum

Click to see larger image.The rate of flow, or discharge, in a river or Great Lakes connecting channel is determined by measuring the channel depth and width, and the velocity of the flow. Measurements can be made by boat, from a bridge, or from a cableway strung across the river. With sufficient measurements of flow over a range of water levels, mathematical relationships can be developed between levels and discharges for various points along the connecting channels and the St. Lawrence River. These equations are essential to the coordination of outflow data, particularly related to hydroelectric power usage of Great Lakes waters.

Graphics: Water level gaging station; measuring outflows at the Niagara Cableway.

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