The Great Lakes are one interconnected watershed, with thousands of rivers and streams draining into the lakes. We can see these surface waters and understand their immensity and flows. What about groundwater, the vast system of aquifers under the Great Lakes? How can we measure its volume and quality, how does it connect with and affect the Great Lakes, and what role does it play in our region’s water security?
These questions and others were considered by the IJC Great Lakes Science Advisory Board’s Research Coordination Committee in a new report, “Great Lakes Surface and Groundwater Model Integration Review: Literature Review, Options for Approaches and Preliminary Action Plan for the Great Lakes Basin.”
The project assessed the feasibility of and need for an integrated surface water-groundwater model for the basin through a literature review and survey, holding an experts workshop, and developing recommendations for a path forward.
The need for a model became clear early in the project, which began in late 2017. Groundwater flows directly into the Great Lakes from rocks and glacial sediment and indirectly via rivers and streams; both sources affect Great Lakes water quality.
For instance, groundwater contaminated by land-use activities can impact drinking water supplies and other uses as well as the health of Great Lakes ecosystems. How groundwater flows into the lakes is critical to understanding how and where this is likely to occur, so sensitive aquifers can be protected from contamination.
The level and timing of groundwater flows into the lakes is also essential from a water quantity perspective. When these flows are understood, the potential for drought and flood conditions can be estimated more accurately. Basin-scale hydrologic changes from changing climatic trends also can be predicted.
“The influence of groundwater on the Great Lakes is not fully understood,” said Yves Michaud, Canadian co-chair of the project and groundwater geoscience program manager for Natural Resources Canada. “This project provided the opportunity for scientists and managers to develop a consensus vision for a binational, shared and unified model for groundwater and surface water.”
Sandra Eberts, the project’s US co-chair and program science coordinator for the US Geological Survey, said, “This model will provide the understanding necessary to help maintain the region’s water security in the coming decades.”
The report outlines several surface water-groundwater parameters the model can identify:
- Groundwater’s contribution to lake level fluctuations and balance
- The effects of climate change on groundwater discharge, streamflow and stream temperature
- Whether water is available and sustainable to meet demands for agricultural and industrial use, drinking water and healthy ecosystems
- Nutrient pathways through the watershed and nutrient loadings to the lakes
- Floodplain management.
Modeling a system as complex as the Great Lakes basin will require several steps. Existing regional models can help to develop a shared concept of the initial model that reflects the basin’s various scales, from a single surface-groundwater watershed based on a river to the entire Great Lakes watershed. Data from various agencies needs to be compared and harmonized so it can provide useful figures of groundwater’s quality, quantity and interaction with surface waters. Finally, a framework must be created to encourage interagency collaboration and agencies working together on the model need to determine how it will be managed over time.
The report provides specific recommendations to move this project from vision to reality:
- Assemble an inter-agency steering committee to create a management framework to catalog activities that could contribute to the model and identify roles for the IJC, the two countries and other stakeholders
- Develop a conceptual model that addresses needs
- Produce a guide for how to create a final model version that incorporates data and provides actual results
- Collaborate and cooperate among agencies, organizations and countries to combine data, funding and expertise that can produce a workable Great Lakes surface and groundwater model.