Water Level Scenarios Summary:

This product is not an official forecast of Great Lakes water levels. Rather, this product is meant to illustrate outcomes that would occur under historical weather and water supply condition, with scenarios chosen based on similarities to recent conditions. For the official forecast, please see our Monthly Bulletin of Great Lakes Water Levels. This tool has been predominantly used to show the possible range of water levels in the upcoming year based on historical hydrologic conditions and water supplies. Beginning in 2021, we will be modifying our scenarios to account for different time periods based on the scenario that is chosen. 

Water levels follow a seasonal cycle where during the fall and early winter, the lakes generally decline due to an increase in evaporation as temperatures decline and cold air moves over the relatively warm lake waters. In the spring and early summer, water levels typically rise due to increased precipitation and enhanced runoff from snowmelt. We refer to the combined effect of precipitation over the lake, evaporation from the lake, and runoff to the lake as Net Basin Supply (NBS). This edition of the Water Level Future Scenarios incorporates the projection of water levels if NBS values are like those experienced in the years in which the warmest winters occurred. Ten NBS sequences are incorporated into this analysis to represent the ten warmest winters and are shown by the purple plume shown in the plots. In addition, three of the years within the purple plume have been called out to show the difference in hydroclimate conditions that could occur over the next 12 months – 1998-99, 2012-13, and 2017-18. ​ The gray shaded area on the plot represents the full range of possible outcomes using historical sequences of NBS from 1900 through 2022.  The most recent coordinated 6-month forecast is also shown for comparison.

Click on the individual graphics to view a larger, printer-friendly image (pdf).




 


 

Click here to obtain the full Great Lakes Water Level Future Scenarios document (pdf)

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.