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Bigger than yours: Green Bay, Twin Ports both claim to have nation's largest freshwater estuary

Whose boast rings true?

Aerial view of St. Louis Bay.
An Aug. 11 aerial view from near Superior’s Billings Park shows part of St. Louis River Estuary, debatably America’s largest freshwater estuary.
Steve Kuchera / Duluth News Tribune
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DULUTH — You could call it a friendly rivalry, but both the Twin Ports and Green Bay make competing claims about the magnificent size of their respective estuaries.

In an introduction to a river restoration initiative, the Minnesota Department of Natural Resources asserts: “At 12,000 acres, the St. Louis Estuary is the largest freshwater estuary in North America and is the headwaters of the Great Lakes.”

Meanwhile, the University of Wisconsin-Green Bay, which is angling for a National Estuarine Research Reserve designation, claims: “Green Bay is the world’s largest freshwater estuary, with significant cultural, economic, commercial and recreational benefits derived from the water and coastal features of the bay.”

So, who’s right?

That depends, according to Deanne Erickson, director of the Lake Superior National Estuarine Research Reserve, established in 2010 and headquartered in Superior.


She said defining the exact size of an estuary can be a subjective process open to interpretation, including how much of the watershed to include.

Erickson said she felt a bit stressed by the line of questioning about which estuary is the largest and also didn’t view the exercise as particularly useful.

“I mean, how do we describe both of these systems as being huge and important, without minimizing one or the other?” she asked as she explained her reluctance to indulge in a game of one-upmanship.

Two geese swimming.
Two Canada geese swim on St. Louis Bay near Indian Point on Monday morning.
Steve Kuchera / Duluth News Tribune

Emily Tyner, director of freshwater strategy for UW-Green Bay, said she, too, doesn’t aim to turn the measurement of the estuaries into a competition, agreeing that it’s not an exact science.

“It certainly is a measure of how big your watershed is, what incoming rivers are going to be counted as part of the estuary, where you think the estuary becomes the lake and how you define that boundary,” she said.

Green Bay’s watershed covers about 40,000 square kilometers, according to Tyner.

“But I think generally, though, there are a lot of interesting similarities between the St. Louis River Estuary and the Green Bay system, and that has become more clear to me as I’ve worked with Deanna and learned about the work they’re doing there,” she said.

Patrick Robinson of the University of Wisconsin Extension system had a hand in creating the Lake Superior reserve and has been watching Green Bay’s efforts to follow suit with keen interest. He explained that it’s difficult to compare the scale of the two estuary systems because of their unique differences.


Fenced exclosures in water.
Exclosures in Kingsbury Bay are designed to help wild rice become re-established in the area. A multi-year, $18 million effort to restore Kingsbury Bay-Grassy Point ended last year. Workers removed invasive narrowleaf cattails and 165,000 cubic yards of sediment from the bay. Much of the sediment was used to restore areas at Grassy Point after a huge amount of sunken, century-old lumber mill waste was removed.
Steve Kuchera / Duluth News Tribune

“In a non-scientific way, I think we should call it a tie, and I’ll be happy. It becomes a bit of a semantics game, because one is a bay of Lake Michigan that has multiple river systems emptying into it. And the other is sort of a classic river entering into Lake Superior with a baymouth bar and embayment behind it. So it’s kind of apples and oranges,” Robinson said.

“They’re both awesome, valuable systems. Let’s leave it at that,” he suggested.

Erickson agreed the composition of the proposed Green Bay estuarine reserve is different than the one established in the Twin Ports.

But, she said: “They both have estuarine functions, and they have very large freshwater systems that are really important for the productivity of the Great Lakes. That’s what estuaries really do: They contribute places to spawn, protected habitats, wetlands and the nutrients that make the Great Lakes productive.”

Robinson supports Green Bay’s efforts to be named a national estuarine reserve on Lake Michigan, becoming the second in the state.

“One of the things I find really exciting is the opportunity for valuable collaborative research, education and outreach between the two reserves, because there are a lot similarities between these two Great Lakes systems," he said. "But there are also differences. We often talk about comparative research, where you have the opportunity to explore important things in two different freshwater bodies from slightly different angles or to learn slightly different things but using a similar comparative research model."

The tributaries that feed Green Bay flow through farm country, and runoff has been a factor in fueling the growth of harmful algal blooms in Lake Michigan.

While agricultural land use is far less prevalent in the St. Louis River watershed, and algal blooms have historically been uncommon in Lake Superior, they have popped up in recent years.


“We may be able to learn thing from the Green Bay system that could be important to understanding where things might head in Lake Superior, and what we can do about it," Robinson said.

Green Bay and the Twin Ports share in common a history of industrial river use that resulted in legacy pollution issues, causing waterways to be listed as “areas of concern,” and Tyner said they may be able to learn from one another’s continuing cleanup efforts.

Boy fishing with ship in the background.
A young angler fishes on Rice’s Point while the M/V American Century moves in the distance.
Steve Kuchera / Duluth News Tribune

Robinson said federal estuarine reserves also gain access to funding, usually to the tune of about $1 million annually.

National Estuarine Research Reserves receive 70% of their funding from the federal government through the National Oceanic Atmospheric Administration. And they typically rely on state governments for the remaining 30% of their support.

“So, what reserves really do is leverage an increase in funding, staff and resources to do research, outreach and promote the stewardship of estuaries,” Erickson said.

“Prior to the reserve existing, we did not have the ability to monitor water quality and take the pulse of the river on a regular basis,” Erickson said, noting that equipping one underwater station with the needed hardware costs about $16,000, and the Lake Superior Reserve has four such stations, monitoring water conditions at different points in the estuary on a continuous basis.

Robinson said such tools can help track the progress being made to improve the health of an estuary and to flag setbacks as they arise.

Kris Eilers, executive director of the St. Louis River Alliance, said much has been done to help the estuary heal.

“What we’re seeing is an area that’s in recovery now. Before, it was devastated by the pollution, and people really lost contact with it," she said. "So, what I’ve seen in the last 10 years is a change in that perception and in the way that we’re able to relate to the river now, because we can actually get out there and touch it."

Duluth Parks Manager Jessica Peterson said that after years of industrial degradation, the St. Louis River is bouncing back and regaining popularity as a recreational resource.

“As a community, we recognized the opportunity to start restoring the St. Louis Estuary to be a clean, safe place to recreate, for habitat restoration and environmental protection," she said. "So, it’s been really exciting to watch partners coming together to make that possible, from the federal to the local levels, including our community partners."

Beaver-chewed stumps.
Stumps left after the tree-felling efforts of beavers stand along the St. Louis River on Monday.
Steve Kuchera / Duluth News Tribune

Peterson pointed to Duluth’s $18 million investment to improve recreational opportunities throughout the St. Louis River Corridor as a significant step forward.

“We have placed an emphasis on healthy, clean, sustainable public spaces," she said. "And this is one of those that’s really important to us. But we can’t do it alone. Certainly other governmental and nonprofit partners play a really big role. And residents play a role in that, as well, in learning about the river and deciding about how they wish to engage with it, take care of it and steward these spaces, as well."

“I think it’s a great success story, and that story is still being written as the work continues,” Peterson said.

Green Bay began its journey to become the 31st member of the National Estuarine Reserve System in 2019, when Gov. Tony Evers submitted a letter of interest to NOAA on the community’s behalf.

Supporters of the would-be reserve are engaged in a site location proposal process at present with the intent to make use of land that is already publicly owned. Tyner said there are no plans to purchase any private property, and if the reserve is created, she assures the designation will force no change in current uses of the estuary for recreational or commercial purposes.

Tyner and her team continue to meet with stakeholders to discuss their efforts to bring a reserve to Green Bay, and she said they hope to receive the final word 2024.

In a National Estuarine Research Reserve system dominated by saltwater locations, Erickson said she’s rooting for Green Bay’s designation as the third federal reserve on the Great Lakes.

“We’re trying to raise the voice of the Great Lakes all the time. So, it’s just awesome to have the Green Bay reserve coming on,” she said.

Peter Passi covers city government for the Duluth News Tribune. He joined the paper in April 2000, initially as a business reporter but has worked a number of beats through the years.
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