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Field trip grants make fourth grade so much better
Great Lakes Echo (2/11)
Pictured Rocks National Lakeshore, in Mich., is one of 186 federal parks to receive a portion of the $1.1 million National Park Foundation grant to set up field trip programs.

State awards $3.6 million in grants to combat invasive species
WLUC-TV, Marquette, MI (2/11)
The Michigan departments of Natural Resources, Environmental Quality and Agriculture and Rural Development announced the award of 19 grant projects totaling $3.6 million, under the Michigan Invasive Species Grant Program.

UT dedicates lab to analyze wide range of research jobs
The Toledo Blade (1/29)
A laboratory that opened in mid-2015 at Ohio's University of Toledo allows monitoring of water quality and detection of dangerous algal toxins in Lake Erie more accurately and faster.

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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