Groundwater: The Sixth Great Lake

Protecting the Vital Resource Beneath Michigan's Ground

Watershed art by Glenn Wolff.

2022 Report—Building Consensus to Protect Michigan’s Groundwater: A Report on the Proceedings and Recommendations of the Michigan Groundwater Table

On June 9, 2022, FLOW published Building Consensus: Securing Protection of Michigan's Groundwater — a report, along with an immersive story map, on the proceedings and recommendations of the Michigan Groundwater Table, which was convened by FLOW and comprised of 22 knowledgeable and influential stakeholders from local government, academia, and regulatory agencies. The report contains consensus findings about the status of Michigan’s groundwater and also recommendations on how to improve its protection related to polluter pay, private wells, agricultural stewardship, statewide septic code, public education, and data tools. Groundwater Table members agreed that Michigan’s groundwater is a “critical and often overlooked resource,” vital to the state’s public health, agriculture and other businesses, coldwater fisheries, stream ecology, and wetlands, and accounts for at least 25% of the total water inflow to the Great Lakes via groundwater inflow into tributaries. They also found that Michigan has underinvested in monitoring, mapping, and reporting groundwater quantity and quality.

2022 Story Map—Groundwater: Michigan's Sixth Great Lake

FLOW unveiled a new groundwater story map in 2022. Bursting with information about the environmental significance of groundwater, the immersive story map takes you on a visual journey from the groundwater basics to unique ecosystems, threats, and protection. Scroll through the image below to view our story map or open it in a new webpage.


March 2022 Livestream: Groundwater–Making the Invisible Visible on World Water Day & Every Day

Click on the image to watch a video of our March 22, 2022, groundwater webinar.

FLOW hosted a livestream event—Groundwater: Making the Invisible Visible on World Water Day & Every Day—on Tuesday, March 22, 2022. The online session offered perspectives on the critical importance of our groundwater resources and the work of the Michigan Groundwater Table, which is convened by FLOW. The Groundwater Table is made up of 22 knowledgeable and influential stakeholders from local government, academia, and regulatory agencies focused on the state of Michigan’s groundwater, the source of drinking water for 45% of Michigan’s population.

FLOW Advisor and Groundwater Table convenor Skip Pruss moderated and lead the discussion, with co-presenters including: Michigan State Rep. Padma Kuppa; Dr. Alan Steinman, Director of the Annis Water Resources Institute at Grand Valley State University; Dave Hamilton, retired MDEQ/TNC groundwater scientist; Andrew Hogarth, retired MDEQ/EGLE site cleanup chief, and Joshua Mosher, Assistant Director, EGLE Remediation and Redevelopment Division. Click here to watch a video of our March 22, 2022, groundwater webinar.


2021 Report—Deep Threats to Our Sixth Great Lake: Spotlighting and Solving Michigan’s Groundwater Emergency

Michigan is “the Great Lakes State” but is a poor steward of the sixth Great Lake, the water lying beneath Michigan’s ground. That water is an immense resource, supplying drinking water to more than four million Michiganders. Despite being a resource so vital to human health and the economy, Michigan’s groundwater is treated inexcusably in both government policy and private practices. Michigan remains the only state in the nation without a statewide septic policy, and PFAS industrial chemicals also pose a critical risk to groundwater and public health. If Michigan is to rely on groundwater to help meet its future needs, it must reform its groundwater practices—and articulate a groundwater policy. The state must protect groundwater from further pollution, rather than allow future contamination to remain in place. Michigan must educate and equip its citizens with basic knowledge and understanding that unseen water is not unimportant water. In fact, it is vital to the quality of life and prosperity of Michigan and the Great Lakes. Learn more in our Deep Threats groundwater report and fact sheet.

Watch our March 10, 2021, Deep Threats webinar featuring FLOW senior policy advisor Dave Dempsey, Dr. Carrie Jennings, who is policy and research director at the Freshwater Society, and Dr. Alan Steinman, the Allen and Helen Hunting Director of the Robert B. Annis Water Resources Institute at Grand Valley State University.

Deep Threats Report - March 2021

Deep Threats Fact Sheet - March 2021

Watch FLOW's March 10, 2021, Groundwater Webinar.

Key Recommendations of the 2021 Report—Deep Threats to Our Sixth Great Lake

Michigan should:

  • Develop and enact a state groundwater policy built on the principle that groundwater must be fully and aggressively protected through a combination of prevention and rigorous cleanup measures.
  • Ban or strictly limit use of chemicals that frequently contaminate groundwater.
  • Reinstate the polluter pay principle in law both to assure polluters are held accountable and to deter future groundwater contamination.
  • Assess fines, penalties, and damages for impairment of the state’s groundwater resource, and require full cleanup by polluters unless technically infeasible.
  • Enact a statewide sanitary code to address more than 130,000 failing systems discharging bacteriological and chemical pollutants to groundwater and surface water, and to prevent further contamination through inspection and maintenance requirements.
  • Establish a fund to assist homeowners, largely in rural areas, in obtaining water well testing.
  • Publish an annual or biennial report, based on a comprehensive public database, that identifies and ranks by hazard all sites of contaminated groundwater or connected overlying land.
  • Direct additional public funding to accelerate the cleanup of Michigan’s groundwater contamination.

2020 Story Map—Groundwater: Michigan's Sixth Great Lake

To foster appreciation of groundwater, FLOW unveiled our groundwater story map in 2020. Packed full of information about the environmental significance of this resource, the story map is a window into one of Michigan’s overlooked assets. Click the image below to view our story map or open it in a  new webpage.

Groundwater: An Often-Forgotten Resource

For generations, schoolchildren in our freshwater region have been taught to remember the names of the Great Lakes with the acronym HOMES, using the first letter of each lake. Maybe they should have been taught to remember them as HOMES-G, FLOW senior policy adviser Dave Dempsey writes in his essay, "Stewardship and the Sixth Great Lake," published by Nature ChangeAlthough the substitute wouldn’t roll off the tongue, it would be appropriate if "G" stood for groundwater. That’s because there is enough fresh water beneath the ground surface of the Great Lakes Basin to match the volume of Lake Huron. In effect, an extra Great Lake lies beneath our feet, often forgotten.

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.

Our Groundwater: Out of Sight, but Not Out of Mind

FLOW's 2018 Groundwater Report

2018 Groundwater Fact Sheet

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.

Learn more in our September 2018 groundwater report, The Sixth Great Lake: the Emergency Threatening Michigan's Overlooked Groundwater Resource, and groundwater fact sheet summarizing our findings.


Key Resources:

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

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 facts about groundwater in our 2018 Groundwater Fact Sheet.


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