Sustainability Podcast Series: Great Lakes Water Levels

The vast majority of the Earth’s fresh surface water is stored in lakes, and the Great Lakes hold a significant portion — about 20 percent — of that fresh water. Drew Gronewold, associate professor in the School for Environment and Sustainability, is working to better understand water level variability on large lake systems, and how climate change and anthropogenic impacts can affect the long term water balance and levels. Most of his work is done “right in our backyard” on the Great Lakes.

Gronewold, who also holds adjunct appointments in the Department of Civil and Environmental Engineering and the Department of Earth and Environmental Sciences, joined Michigan Minds for a special series focusing on sustainability research and efforts at the University of Michigan.

“Eighty percent of the Earth’s fresh, unfrozen surface water is in just 10 large lakes across the Earth, including the Great Lakes. So, from a global water abundance and availability perspective, you need to look to lakes. If we can understand how water moves through and is stored in the Great Lakes, we’ll have a really strong ability and basis for understanding how that works on other large lake systems, and ultimately, the vast majority of earth’s fresh surface water,” Gronewold explains.

He also discusses the coastline of the Great Lakes and how it is one of the primary ways we interact with the lakes. As those water levels change, whether it’s short-term or long-term, it has a direct impact on those who live on the coastlines and the interaction of ecosystems through the coastlines.

The Great Lakes also play an important role in the regional and national economy. Gronewold says that local economists have said the Great Lakes have an economy close to $6 trillion and that if the Great Lakes were their own country pulling together the states and the Canadian provinces they border, it would make the third largest economy in the world. A lot of that is based on the resources the lakes provide, including shipping.

“We all see those vessels criss-cross in the Great Lakes. Their ability to do their jobs is entirely dependent on the water levels of the Great Lakes. Their capacity to ship goods and cargo depends directly on water levels, particularly in narrow and shallow portions of the Great Lakes,” he says.

The recreational aspects of the Great Lakes also contribute to that economy — boating and fishing, for example — and are great examples of how water levels can affect the economy and the industry, he says. When levels get high, marinas experience difficulties as docks and boats can get lost.

Gronewold and his research team use modeling tools to develop simulations of how water flows through the Great Lakes. They use data from historical records that date back to the mid-1800s.

“We blend historical water level data with other data that’s available on things like precipitation or evaporation or the amount of water flowing into the lakes through rivers and streams. The vast majority of that information is collected by federal agencies like the United States Geological Survey or the National Oceanic and Atmospheric Administration, or even the Army Corps of Engineers. And the fact that that data is more or less readily available, and that we can pull it into our models, is one of the key things that we rely on in our research.”

They use this research and knowledge to create forecasts of water levels over different time periods to understand the relationship between things like evaporation, water demand, and changes in precipitation and water levels. They develop these forecasts to help with planning decisions moving forward with a deeper understanding of the past.

Gronewold says there has been “profound change” in the past 10 years regarding water variability — most notably in evaporation. He explains that when lake temperatures get high, evaporation goes up and there has been a surge in precipitation over the past five to 10 years making it the wettest decade on record for much of central North America and the Great Lakes.

The positive, he says, is that the research that is being conducted at U-M and with federal agencies, as well as others being dedicated to this research and education, is having a positive impact. However, people’s ability to forget the past is upsetting, he notes. Especially with a long historical water level record available to use.

He ends the podcast with two takeaways for listeners: serious discussions in the public realm need to take place about the Great Lakes coastline and there need to be long-term decisions made about the future of the Great Lakes overall.

“We have a huge socioeconomic discrepancy in who owns and interacts with and makes decisions about the coastline. And I don’t think it’s okay, particularly from a long-term sustainability perspective. A broader sector of the public needs to have access to the Great Lakes coastline, and needs to be involved in decisions about how they’re managed and where people can build homes, where commerce can establish themselves.”

“We need to be making some long term decisions about the future of the Great Lakes, a multi-decadal time scale,” Gronewold says. “We have a strong gradient or discrepancy in water surplus and water scarcity in this country. The arid Southwest is hot, dry, on fire, and losing water at an alarming rate. It is absolutely critical that we, as a region, have a clear understanding of what role the Great Lakes is going to play in both national, United States, binational and including indigenous communities, water scarcity, and water abundance over the next 20, 40 years, so we can be making good, sustainable decisions and not be caught off guard if a crisis occurs.”


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