Coordinated Great Lakes lake-wide beginning of month water levels

This dataset consists of lake-wide beginning of month water levels for Lakes Superior, Michigan-Huron, Saint Clair, Erie, and Ontario. The data are presented in meters with reference to the International Great Lakes Datum (IGLD) 1985. The dataset is computed and stewarded by Environment and Climate Change Canada (ECCC) and the United States Army Corps of Engineers (USACE), under the auspices of the Coordinating Committee on Great Lakes Basic Hydraulic and Hydrologic Data (Coordinating Committee)1. Each agency independently computes and manages their own version of the dataset. The data are binationally coordinated annually, where ECCC and USACE compare their versions to verify that they are consistent. 

The beginning of Month water level for Lake Michigan-Huron is calculated by averaging the daily mean lake-wide average water level from the first day of the month and the last day of the previous month. The begining of month water levels are computed from hydrometric observations collected from a network of gauging stations located around each lake and on both sides of the Canada-United States border. The gauges are owned and maintained by the Canadian Hydrographic Service (CHS)2 and the National Oceanic and Atmospheric Administration (NOAA)3.  

Detailed metadata and data files for each lake are provided within this dataset. The data files are in comma separated value format (CSV). The CSV data files contain both the beginning of month water level and concise metadata described in accordance with the Climate and Forecasting (CF) conventions. The detailed metadata is in PDF format and provides extended descriptions of data sources, computation methods, dataset history, and related information for each great lake.   

This dataset is updated annually with the addition of the most recent complete calendar year of data.  The version number reflects the year of the last available data.  However, note that as well as adding the most recent data, data from previous years may be adjusted based on updated information from those years.

1Coordinating Committee on Great Lakes Basic Hydraulic and Hydrologic Data https://www.greatlakescc.org/en/home/ 

2DFO 2024. Marine Environmental Data Section Archive, https://meds-sdmm.dfo-mpo.gc.ca, Ecosystem and Oceans Science, Department of Fisheries and Oceans Canada. 

3NOAA 2024. Tides and Currents, https://tidesandcurrents.noaa.gov/, Center for Operational Oceanographic Products and Services, National Oceanic and Atmospheric Administration.