The Great Lakes Water Balance
Data Availability and Annotated Bibliography
By Brian P. Neff and Jason R. Killian

Introduction | Hydrological Information | Forecasts and Summary

Change in Storage 

Change in storage calculations are based on a net change in stage data and the surface area of each Great Lake. An official accounting of the surface area of each of the Great Lakes, Lake St. Clair and all connecting channels is reported by CCGLBHHD (1977).

Lake Levels 

Measurement of Great Lakes water levels is not a straight forward procedure. Phenomena such as wind set up and seiche can cause considerable variation in the water level within each lake. Croley (1987) offers a description of these and other difficulties in measuring Great Lakes water levels. The Croley (1987) study also describes strategies to minimize error in measuring Great Lakes water levels.

Canadian Data 

All Canadian Great Lakes stage data collected by the Department of Fisheries and Oceans are managed and archived by the Marine Environmental Data Service (MEDS). This includes 27 distinct historical records of stage measurements in various locations throughout the Great Lakes region (figure 13). MEDS assures the quality of its products and historical records are kept up to date. Lake levels are measured hourly to a resolution of 1 mm and reported to the nearest cm. Daily and monthly averages are calculated from hourly data; daily data are reported to a resolution of 1 cm, and monthly averages are considered reliable to ± 1 mm. Lake level data are available directly from MEDS, and is also published on the HYDAT CD-ROM. 

United States 

Data The National Ocean Service (NOS), a subsidiary of NOAA, monitors water levels of the Great Lakes on the US side. NOS maintains a number of gages on each lake (figure 13). Measurements are taken to the nearest mm and reported to the nearest cm. The official accuracy of these measurements is ±5 mm. Data are archived by the Center for Operational Oceanographic Products and Services (CO-OPS) and can be obtained directly from their Silver Spring, MD office. 

The USACE also reports "normalized daily mean" water levels of the great lakes on behalf of the Lake Superior, Niagara and the St. Lawrence River International Boards of Control. These values are generated from a coordination of the measurements of selected US and Canadian gages and are based on the datasets outlined above. Official normalized daily mean data can be obtained from the USACE, Detroit District office of Great Lakes Hydraulics and Hydrology. The USACE does not offer a statement of uncertainty for these data. 

Thermal Expansion and Contraction 

In most lake water balance calculations, the change in water storage due to the thermal expansion and contraction of water is not calculated. However, some researchers have shown that this can become significant during some months of the year (Meredith 1975, Quinn and Guerra 1986) and have recommended that thermal expansion / contraction be considered in net basin supply calculations (Lee 1992). Sufficient water column temperature data does not exist to calculate the thermal expansion and contraction of most of the Great Lakes and for most years. Limited amounts of water profile data are published in Meredith (1975) and Schertzer (1987).

References

• Bibliographies of selected references

• Full reference list

• Sources of Hydrological data and information

This report is prepared by USGS in cooperation with the Great Lakes Commission.

The Great Lakes Commission is a  multi-agency, multi-disciplinary, multi-faceted team approach to addressing the science and policy of a Great Lakes water management regime will produce such application-oriented products as a water use web site, updated annual water use inventories, ecological evaluations of the system, and an integrated binational role for future Great Lakes-St. Lawrence endeavors.