The Sixth Great Lake

Groundwater, although vitally important to Michigan's economy and public health, is often overlooked. Because groundwater is out of sight, its widespread contamination can go unnoticed. Yet 45% of the people of Michigan get their drinking water from groundwater. And 20% to 40% of the volume of the Great Lakes originates as groundwater.

FLOW is committed to educating Michigan citizens about the importance and value of groundwater and driving public policy changes that strengthen its protection. It is vital to our mission because it connects with and feeds surface water, which is protected by the public trust doctrine.

We call groundwater the Sixth Great Lake because the volume of groundwater in the Great Lakes basin is approximately equal to that of Lake Huron. Just as we devote special care to the five surface water Great Lakes, we need to devote ourselves to protecting the sixth.

Key Resources:

Full Groundwater Report


Groundwater Report Summary

To foster appreciation of groundwater, FLOW is unveiling our groundwater story map. Packed full of information about the environmental significance of this resource, the story map is a window into one of Michigan’s overlooked assets.

Michigan is “The Great Lakes State” but is a failing steward of the sixth Great Lake, the water lying beneath Michigan’s ground. FLOW is calling for state-level reforms to strengthen protection of Michigan’s groundwater. That includes statewide monitoring of septic systems.


Michigan needs stronger septic protections

FLOW Podcast: Groundwater Connection, written and edited by Sally Eisele

What lies beneath? In FLOW’s new Groundwater Connection podcast, veteran journalist Sally Eisele seeks out the sites and science of groundwater pollution and protection Up North in Michigan. Listen in on her traveling reflections and conversations with children, scientists, community members, and policy experts. During National Groundwater Awareness Week, this is a part of FLOW's efforts to take a good look at the Sixth Great Lake, the groundwater beneath us.

In this video by Joe VanderMeulen, FLOW addresses our Sixth Great Lake, the invisible resource of groundwater. While it remains unseen and largely taken for granted, it is essential to our livelihood and must be respected and protected.

The Artists Behind “I Am Groundwater”

Narrator Anne-Marie Oomen is author of Lake Michigan Mermaid with Linda Nemec Foster (Michigan Notable Book for 2018), Love, Sex and 4-H (Next Generation Indie Award for Memoir), Pulling Down the Barn (Michigan Notable Book); and Uncoded Woman (poetry), among others.  She recently edited ELEMENTAL: A Collection of Michigan Nonfiction.  She teaches at Solstice MFA at Pine Manor College (MA), Interlochen’s College of Creative Arts (MI), and at conferences throughout the country. 

Artists Glenn Wolff and Anne-Marie Oomen

"When Dave Dempsey referred to Michigan's ground water as the sixth great lake, that sank in (pun intended).  I realized our ground water is a whole other body of water, equally as important as our visible water.  I realized ground water is invisible but it is not a ghost--rather, literal and deep.  Though it has its mysteries, we rely on it even more than we do our visible lakes. Its invisibility makes ground water vulnerable; we can't see what we're doing to it, and so we ignore the dangers, until the PFAS threat rises--among others.  The words of Joe Vandermeulen's poem, which I was so honored to read, say it best. "This is what you must know. What is done above can reach the water below and will join my slow, inexorable flow."  I grew up on a farm where we relied on deep wells to irrigate our family's fields--which ultimately feed people. When I think about that, about how we needed that water to keep the fields going, and how important it was that the water was good, I hear Joe's words again, "Though invisible, I am part of the great water cycle, giver and sustainer life."  When will we realize that we too, with all our needs for water, are part of the cycle?  When I saw Glenn's incredible painting, saw how his painting zeros in at last on the child digging in the sand, that child became the link between what is underground and what we do above ground. FLOW is asking us to pay attention, and gosh we need to do it now, and quickly."  

Artist Glenn Wolff grew up in Traverse City, Michigan. He studied Printmaking at Northwestern Michigan College, and received his BFA from the Minneapolis College of Art and Design. His career began in New York City as an illustrator for The New York Times, The Village Voice, The Central Park Conservancy, The New York Zoological Society, Audubon, and numerous book publishers.

He now lives and works in Northern Michigan concentrating on fine art, book projects, and music, and is on the full-time art faculty at Northwestern Michigan College. He has been a frequent collaborator with author Jerry Dennis, and numerous environmental organizations including GTRLC, FLOW, Leelanau Land Conservancy, TART Trails, Wings of Wonder, and Groundwork Center. His mixed media artwork is represented by Tamarack Gallery in Omena, Michigan.

“I grew up roaming the beaches, rivers, and communities of our peninsulas as a kid. I feel lucky that I was able to return here to raise a family and make my way as an artist. I am continuously in awe and am grateful for the work that FLOW does to preserve and promote water quality, rights, and justice for the Great Lakes. It was an honor when Joe VanderMeulen asked me to collaborate with FLOW and Anne-Marie Oomen to help illustrate the conversation around groundwater.”

About Michigan's Groundwater

The volume of groundwater in the Great Lakes watershed is roughly equal to the volume of Lake Huron. Often overlooked because it is out of sight, Michigan’s groundwater is an immense asset and life-giving resource.

Michigan has the most private drinking water wells drilled annually of any state. About 45% of the state’s population depends on groundwater for its drinking water. Daily groundwater withdrawals in Michigan total over 260 million gallons for irrigation as well as 64 million gallons from on-site wells for industrial purposes. As much as 42% of the water in the Great Lakes originates from groundwater.

For a resource so vital to human health and the economy, Michigan’s groundwater is shabbily treated in both policy and practice, putting both public health and the environment at risk. Learn more about groundwater here.


Why Groundwater?

Michigan’s groundwater is compromised and deteriorating. Our groundwater is plagued by widespread pollution, with over 3,000 groundwater sites whose contamination is so severe that state law bars their further use. 

Some may argue it is too costly to clean up and protect Michigan’s groundwater, but it is costlier to ignore the problem. We are transferring these increasing costs to our children and future generations. The state has not yet reckoned with cleanup costs for contaminated groundwater, let alone the costs to public health and infrastructure.

The state of Michigan’s groundwater will not improve without changes in policy and practice.





“Michigan is sitting atop a groundwater resource that already serves the needs of millions of us for drinking water and so much more – but state policy treats it as if it is replaceable. It is not.”

- Dave Dempsey

Key Recommendations of the Report:

Michigan should:

  • Identify a long-term funding source to clean up > 6,000 remaining sites with contaminated groundwater and no responsible party.
  • Aggressively prevent, detect and clean up nitrate pollution & assist rural communities in obtaining safe, nitrate-free drinking water.
  • Improve groundwater data collection & reporting, including a statewide groundwater education program.

The Michigan Legislature should:

  • Stop creating legal “sacrifice zones” where groundwater use is restricted or banned. Whoever contaminates the groundwater should be required to restore it – or pay damages to the state.
  • Set aside funding so that all residential well owners can test their well water samples.
  • Require all septic systems to be routinely inspected and maintained.

The Michigan Department of Environmental Quality should:

  • Publish a biennial report on the state of groundwater in Michigan, mapping and ranking the 100 contaminated groundwater sites that pose the greatest risk to human health and the environment.