LEVELnews: monitoring Great Lakes and St. Lawrence River water levels

LEVELnews is a newsletter that provides a monthly update on Great Lakes and St. Lawrence River water levels. The most recent editions of LEVELnews can be requested via the links below. Older editions of LEVELnews can be found in the Government of Canada Publications Catalogue, or contact ec.LEVELnews-infoNIVEAU.ec@canada.ca

A note on projections

Predicting future lake levels can be a benefit for many that live around and use the Great Lakes. In order to estimate where lake levels may be in a few months, water resources engineers look to measurements of the Great Lakes made in the past. Based on the record of Great Lakes levels (1918–Present), changes to lake levels can be predicted for a range of wet and dry conditions. If you look at the water levels graphs in the Canadian Hydrographic Service’s monthly water levels bulletin (The Canadian Hydrographic Service (waterlevels.gc.ca)) you will note a “Probable Range of Future Levels” depicted by dashed lines on the included figures. The red dashed line is a prediction of water levels if relatively wet conditions are encountered and lake levels are expected to be above these values 5% of the time.  The blue dashed line is a prediction of lake levels if relatively dry conditions are encountered and lake levels are expected to be below these values 5% of the time. The levels between these two lines is the “Probable Range of Future Levels”, which is based on the recorded history of the lakes.  This is the range that we would expect lake levels to be within 90% of the time.

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