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Monthly Bulletin of Great Lakes Water Levels

We do not have the ability to offer email updates at this time.  The Monthly Bulletin is updated by the 5th or 6th day of each month.

Six-Month Forecast Bulletins

Water levels for the previous year and the current year to date are shown as a solid line on the hydrographs. A projection for the next six months is given as a dashed line. This projection is based on the present condition of the lake basin and anticipated future weather. The shaded area shows a range of possible levels over the next six months dependent upon weather variations. Current and projected levels (solid and dashed lines) can be compared with the 1918-2020 average levels (dotted line) and extreme levels (shown as bars with their year of occurrence). The legend below further identifies the information on the hydrographs.

The levels on the hydrographs are shown in both feet and meters above (+) or below (-) Chart Datum. Chart Datum, also known as Low Water Datum, is a reference plane on each lake to which water depth and Federal navigation improvement depths on navigation charts are referred.

All elevations and plots shown in this bulletin are referenced to International Great Lakes Datum 1985 (IGLD 1985). IGLD 1985 has its zero base at Rimouski, Quebec near the mouth of the St. Lawrence River (approximate sea level).

Click here to obtain the full Monthly Bulletin of Lake Levels for the Great Lakes, including last month's basin hydrology (pdf)

Click on the individual graphics to view a larger, printer-friendly image (pdf). 6-month Lake Superior Forecast Graphic 6-month Lakes Michigan-Huron Forecast Graphic 6-month Lake St. Clair Forecast Graphic 6-month Lake Erie Forecast Graphic 6-month Lake Ontario Forecast Graphic

Click here to obtain the full Monthly Bulletin of Lake Levels for the Great Lakes, including last month's basin hydrology (pdf)



Basin Hydrology Summary and Monthly Water Level Summary

For more information about basin conditions, please go to the Great Lakes Basin Conditions page.

Guide to the Monthly Bulletin

Detroit District Disclaimer

NOTICE: All data contained herein is preliminary in nature and therefore subject to change. The data is for general information purposes ONLY and SHALL NOT be used in technical applications such as, but not limited to, studies or designs. All critical data should be obtained from and verified by the United States Army Corps of Engineers, Detroit District, Engineering and Construction Division, Hydraulics and Hydrology Branch, 477 Michigan Ave., Detroit, MI 48226. The United States of America assumes no liability for the completeness or accuracy of the data contained herein and any use of such data inconsistent with this disclaimer shall be solely at the risk of the user.

Document Information and Assistance

NOTICE:  Not all documents accessible via this page are readable using optical character recognition (OCR). For more information and/or assistance please call 313-226-6441.