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Great Lakes Water Levels




Great Lakes Water Level Observations

Measurement of Great Lakes Water Levels

The Center for Operational Oceanographic Products and Services (CO-OPS), part of NOAA’s National Ocean Service (NOS), is responsible for operation and maintenance of the National Water Level Observation Network (NWLON). The NWLON provides water level and meteorological data for the ocean and Great Lakes coasts. CO-OPS operates 53 water level stations on the Great Lakes and their connecting channels.  Historic records for some of these stations date back to 1860, providing over 150 years of continuous data. Great Lakes water levels are measured from an elevation reference point referred to as the International Great Lakes Datum (IGLD), presently IGLD 1985. This datum is referenced to sea level as measured at Rimouski, Quebec, near the mouth of the St. Lawrence River. Every 25-30 years, the IGLD is updated to account for crustal movement – the rebound of the earth’s crust from the weight of the glaciers.

Some 23 of the 53 Great Lakes stations are now configured with a variety of meteorological sensors and 13 stations are now operating Continuously Operating Reference Station (CORS) GPS antennas.  The standard is shown in the example below for the Great Lakes NWLON station located at Mackinaw City, MI

NOS water level gauging station

Photo credit: Jeff Oyler, NOAA CO-OPS

The Canadian Hydrographic Service maintains 29 water level gauges on the Great Lakes and 27 on the St. Lawrence River.