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A Fluid Concept: Modeling the Complicated Relationship Between Great Lakes Groundwater and Surface Water

Picture of Allison Voglesong Zejnati
Allison Voglesong Zejnati
groundwater flint tributary

Because it’s largely unseen, it may be difficult to imagine that the volume of groundwater in the Great Lakes basin is about equal to the volume of Lake Michigan. These vast underground reservoirs play an important role linking the Great Lakes to the land, streams, wetlands and people in the basin’s watersheds.

However, “The extent to which groundwater quantity and quality affect the overall function of the Great Lakes system is currently unknown,” according to a 2021 United States Geological Survey report on the Great Lakes’ science needs.

From growing demands for groundwater from agricultural, residential and industrial uses, to the predicted decreases in summer groundwater supply leading to decreased groundwater recharge, it is more important than ever to better understand the complicated relationship between Great Lakes groundwater and surface water.

To enhance our knowledge of how groundwater and surface water interact, managers and researchers need to figure out how to combine data into a single, integrated model of the system. In its latest report, the International Joint Commission (IJC) Great Lakes Science Advisory Board-Research Coordination Committee describes a conceptual framework for an integrated Great Lakes groundwater-surface water numerical model.

If that sounds highly technical, it is.

Think of it this way: Artists like Glenn Wolff can help us visualize the interplay between Great Lakes groundwater and surface water, as depicted in this illustration commissioned by Michigan-based nonprofit FLOW.

flow groundwater surface water wolff

FLOW commissioned this conceptual integration of groundwater and surface water by Michigan artist Glenn Wolff. Credit: FLOW

Similarly, numerical models are their own kind of art form that researchers and scientists use to scientifically conceptualize the many variable components of Great Lakes groundwater or surface water resources.

“The project did not develop an actual numerical model, but rather it developed the critical components of a conceptual framework that is necessary to guide development of such a model in the future,” said project co-lead Sandy Eberts. Eberts is a Science Advisory Board-Research Coordination Committee member, professional hydrogeologist and the Earth Systems Processes Division director for the US Geological Survey’s Water Resources Mission Area.

“Most of what the project looked at was how to develop these groundwater and surface water coupled models that would really focus on the hydrologic cycle, with an eye towards using that foundational understanding of the water budget to simulate and understand and forecast water quality,” said Eberts.

The board’s project surveyed experts and stakeholders to develop the management, scientific and technical elements of the conceptual framework. Just as an artist might conceptualize their final product by first sketching it on the canvas before actually painting, the conceptual framework outlines the elements needed for an actual integrated model, before software and datasets get put to work crunching numbers and generating results. It’s intended to guide future efforts that would build an actual basinwide integrated groundwater-surface water numerical model.

The resulting feedback identified key beneficial outcomes of developing an integrated groundwater-surface water numerical model, including that it would help to better understand tributary baseflows, it would support implementation of the Great Lakes-St. Lawrence River Sustainable Water Resources Agreement, it would provide additional context for regional and local water managers, it could help improve water quality models and it could be used to enhance representation of the Great Lakes in climate change models.

The report identifies the next steps for researchers, government agencies and others to create an integrated model. The board recommends that the IJC, Great Lakes Commission and Annex 8 (Groundwater) Subcommittee of the Great Lakes Water Quality Agreement work together and support a future binational collaborative entity focused on creating an actual basinwide integrated groundwater-surface water numerical model.

“The entity would facilitate information exchange across disciplines and jurisdictions, maintain a listing of supporting projects, subject matter experts, representatives of key stakeholder constituencies and potential funders as well,” said project co-lead Réjean Couture. Couture is a Science Advisory Board-Research Coordination Committee member and director of the Geological Survey of Canada’s Quebec City Office at Natural Resources Canada.

If you are interested in learning more about this project or are an interested stakeholder eager to participate in future development of an integrated groundwater-surface water numerical model, contact Lizhu Wang via

Picture of Allison Voglesong Zejnati
Allison Voglesong Zejnati

Allison Voglesong Zejnati is public affairs specialist at the IJC’s Great Lakes Regional Office in Windsor, Ontario.

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