It can be tempting to think of the Great Lakes as 5 big bathtubs – 5 uniform masses of water that each face one set of problems, or are each home to one list of fish no matter where you’re dropping a line. But, the Great Lakes cover nearly 100,000 square miles, span a full 10 degrees of latitude and range 1,300 feet in depth. Any environmentalist working on polluted runoff or any fisherman worth his or her (non)salt will tell you: The problems and possibilities in one section of a lake aren’t the same ones you’ll find 50 miles north or 10 miles offshore.

This can be hard for scientists, who need to compare similar regions to get answers to important questions. Are a certain species of fish not thriving because of a nearby source of pollution? Or is it because the habitat isn’t right? You can’t study the effects of pollution in one area, 10 feet deep and near a river mouth, by comparing it to an unpolluted area that’s miles offshore.

So, what can be done? All parts of Lake Erie’s western basin, for example, don’t provide similar habitats. BUT, one part of Lake Erie’s western basin might look a lot like an area in Saginaw Bay. If only one of these similar areas is being impacted by a certain pollutant, that’s a good setup to study the effects of that pollutant, because other factors (like depth or temperature) are being held constant.

Scientists and resource managers have been making this leap for ages – finding areas in the Great Lakes that are relatively alike and comparing them – everything from fish stocking efforts to the spread of invasive species. But now, there’s a tool to make it easier. Scientists have developed what is basically an atlas of ecologically similar areas in the Great Lakes.

Researchers have developed a classification system for the Great Lakes that groups regions with similar characteristics. Credit Lacey Mason/GLAHF

Based on four main variables (depth, temperature, motion from waves and currents, and influence from nearby tributaries) researchers from multiple institutions (including NOAA Great Lakes Environmental Research Laboratory) organized the Great Lakes into 77 Aquatic Ecological Units (AEUs). The classification system took 6 years to create and incorporates multiple NOAA datasets, including depth, temperature patterns and circulation patterns throughout the lakes.

Each AEU is a chunk of the lakes with its own unique combination of those four variables. The idea is that scientists and conservation professionals working within one type of AEU will be comparing apples to apples.

Ecosystem classification isn’t new – it’s been applied to land and ocean environments before. But, this is the first classification system developed for the Great Lakes.

Catherine Riseng, a researcher with the University of Michigan’s School for Environment and Sustainability, is lead author on the paper. She tells us the work “simplifies a complex ecosystem”.

“It can be used by researchers to help describe and explain existing ecological patterns and by resource managers to facilitate inventory surveys, evaluate the status and trends, and track the effects of human disturbance across different types of ecological units”, she says.

The work was done as part of the Great Lakes Aquatic Habitat Framework (GLAHF), which is “a comprehensive spatial framework, database, and classification for Great Lakes ecological data.”

The classification data will soon be available for download at https://www.glahf.org/classification/. For now, you can interactively explore the AEUs and related datasets at https://glahf.org/explorer/.

A project update from GLERL Deputy Director, Jesse Feyen

GLERL has a long track record for modeling and predicting circulation and levels for our Great Lakes waters. Now we are working to apply this expertise in Lake Champlain, a large lake system that is shared with Canada. The lake lies along the New York/Vermont border and flows north into Quebec via the Richelieu River. In 2011, this lake-river system experienced significant precipitation and wind events that raised the levels of Lake Champlain to record levels and caused extensive flooding and damage around the lake and along the Richelieu River.

As a cross-border boundary water, management of the Lake Champlain/Richelieu River system is subject to the International Boundary Waters Treaty. In responding to a reference from the governments of the United States and Canada, the binational International Joint Commission (IJC) is conducting a study exploring the causes, impacts, risks, and solutions to flooding in the basin like during 2011.

The IJC has tapped GLERL to play a lead role in the study given our expertise in modeling the hydrology and hydrodynamics of the Great Lakes and experience working with Canadian partners. As a key expert in the IJC’s Upper Great Lakes Study and the Lake Ontario-St. Lawrence River Study, GLERL Director Deborah Lee was invited to serve as a U.S. member of the project’s Study Board, which provides the overall guidance and direction for the project. Deborah nominated Deputy Director Jesse Feyen to head up the U.S. portion of the study’s Hydraulics, Hydrology, and Mapping Technical Working Group, or HHM TWG.

A GLERL-led team of research partners is building solutions to these flooding issues in Lake Champlain and Richelieu River System. In addition to Lee and Feyen, team members include Integrated Physical and Ecological Modeling and Forecasting (IPEMF) Philip Chu, Drew Gronewold, and Eric Anderson; Cooperative Institute for Great Lakes Research (CIGLR) Dima Beletsky, Haoguo Hu, and Andy Xiao, with support from Lacey Mason; and the Northeast River Forecast Center’s Bill Saunders.

The two priorities of the study are to determine what flood mitigation measures can be implemented in the basin, and to create new flood forecast tools for the system. Current flood models operated by the National Weather Service (NWS) cannot account for the effects of winds and waves on Lake Champlain water levels, which can increase water level by several feet, significantly impacting flooding.

The modeling approach used in this study mirrors GLERL’s work in the Great Lakes. In Lake Champlain, a 3D FVCOM is being built to model water levels, temperature, and circulation; a WAVEWATCH III wave model will be coupled to FVCOM model to predict wave conditions; a WRF-Hydro (Weather Research and Forecasting) distributed hydrologic model will predict streamflow and runoff into the basin. This approach relies on models that are in use at NOAA and can readily be transferred to operations by the NWS and National Ocean Service, both of which have been participating in planning throughout the project.

While flooding issues in the Lake Champlain and Richelieu River system pose steep challenges on both sides of the border, GLERL brings the leadership, technical expertise as well as a “One NOAA” approach that are all essential for leveraging progress.