Current Water Levels
The U.S. Army Corps of Engineers (USACE) and Environment Canada jointly monitor and forecast water levels on the Great Lakes. Information is compiled and disseminated on the USACE Detroit District website. For the most up-to-date information on current water levels of the Great Lakes, visit the U.S. Army Corps of Engineers website.
The water levels of the Great Lakes are determined based on a network of water level gages located around each Great Lake. These gages are maintained by the National Ocean Service in the United States and the Canadian Hydrograph Service in Canada. Their locations were selected based on their data record, geography and accessibility. They are spread around each lake in order to provide a lake-wide water surface elevation. The U.S. Army Corps of Engineers (USACE) is responsible for collecting and disseminating information on Great Lakes water levels.
Records are based on monthly average water levels and not daily water levels. In addition to the all-time record lows, each month has a minimum and maximum water level that is reflective of the seasonal fluctuations of the lakes.
Water levels around the Great Lakes Basin have been measured since the 1860s. Early measurements were not comprehensive so the official period of records for Great Lakes water levels goes back to 1918.
By studying beach ridges along Lake Michigan, as well as radiocarbon dating of soil core samples, scientists have developed a 4,700 year record of Lake Michigan-Huron water levels. From analyzing this data, scientists identified a general rise and fall cycle that lasts approximately 120-200 years. They also learned that there is a shorter-term fluctuation from 29-38 years (averaging about 32 years) that occurs within the longer cycle.
Future Water Levels
In addition to measuring water levels in the Basin, mathematical relationships have been generated between the measurements of water levels and the rate of flow within the connecting rivers of the Great Lakes system in attempt to predict future water levels. The models are able to generate forecasts of water levels for each lake. However, these forecast models fundamentally depend on accurate seasonal variations of weather patterns. Because there is large variability in weather forecasting, water levels can vary widely from what is predicted.
The United States Army Corps of Engineers (USACE) provides a range for future water levels. This projection is based on the present condition of the lake basin and anticipated future weather. The forecasts fall within the range 90% of the time. However, a significant weather pattern shift can alter lake levels enough for levels to fall outside of the forecasted range. USACE provides Weekly Great Lakes Water Levels information that includes an update on current water levels conditions, weather, and outflows and a forecast of water levels over the upcoming month as well as a Monthly Bulletin of Great Lakes Water Levels which is a six-month forecast of Great Lakes water levels.
These water level forecasts can be accessed at: http://www.lre.usace.army.mil/greatlakes/hh/greatlakeswaterlevels/waterlevelforecasts/