Michigan’s aquifers and their importance

By Stacy Gittleman

This summer, if you find yourself on a sandy shore, take a shovel and start digging. Chances are you will hit water. This science experiment from our childhood is the simplest way to understand aquifers.

When water infiltrates the ground, it can either be held in the surface soil and used by plants, evaporate, or trickle down into the earth through mineral deposits until it reaches a layer of impervious rock or clay that it cannot travel through – the saturated zone. This subterranean water reserve is known as groundwater, an estimated one third of which replenishes the country’s surface waters.

The U.S. Geological Survey (USGS), the nation’s key provider of mapping out of the nation’s geology and hydrology, describes aquifers as spongy, porous rock formations that store and transmit water through connected pores. Important for recharge, aquifers can feed hundreds of groundwater wells and streams.

There are two main classifications of aquifers. Bedrock till aquifers are made up of different rock types and are covered by till, a residual glacial mix of rocks, sand, silt and clay. A bedrock aquifer can yield as much as ten gallons of water per minute – enough for a small business or single-family home. The major water transport in bedrock till aquifers occurs in the fractures and faults of the underlying bedrock.

In Michigan, communities with public water supplies in bedrock aquifers include the cities of Lansing, Jackson, the campus of Michigan State University, Marshall, Vassar and Nahma Township. All are supplied by water coming from around 75,395 wells and have a capacity of 55 million gallons daily (mgd). In these areas of the state, the water flow rate can be as slow as eight to 10 gallons per minute. In contrast, a typical modern three-bedroom home requires 15-20 gallons per minute for great water pressure in the shower or for washing machines and dishwashers to operate properly.

A glacial aquifer, also called a stratified drift aquifer, is comprised of layered deposits of sand, gravel, silt and clay formed thousands of years ago by the receding glaciers. Glacial aquifers can provide millions of gallons of water daily wherever deep saturated deposits of porous sand and gravel are found. Glacial aquifers supply water through a public well system to cities and municipalities including Kalamazoo, Adrian, Cadillac, Claire, Hillsdale, Fenton and Kinross, coming from 207,407 wells and can produce around 61.5 million gallons daily (mgd).

For aquifers to remain productive, they must receive percolated water from rainfall or snowmelt. This is known as groundwater recharge.

Groundwater recharge is estimated by the USGS in inches per year. According to USGS studies dating to 1996, aquifers in southeast Michigan recharge on average between 2.1 and four inches per year. But there are some aquifers in the western part of the state that have been severely over-pumped. There, a hard layer of clay is preventing precipitation from rainwater and snow melt from reaching and replenishing the aquifer.

According to the USGS, groundwater supplies 38 percent of the drinking water in the United States and half of the global drinking water supply. Seventy percent of groundwater is used for agriculture. The USGS estimates groundwater replenishes 30 percent of the nation’s surface water flow. The volume of naturally cool groundwater that flows into a river or stream, called the baseflow, regulates ideal surface water temperatures in Michigan’s rivers to maintain fish populations. The cooler the water, the more oxygenated the stream to support aquatic life like trout, the state’s most prized gaming fish.

In addition to drawing water for our homes and farms, the naturally cool temperatures of groundwater also maintains the proper temperature of data centers that power the internet and propel forward industries such as energy, mining and manufacturing.

In March 2024, the Michigan environmental organization For the Love of Water (FLOW) released its annual Michigan groundwater report and raised the alarm about our dependency on groundwater and how it is running dry in some regions of the nation. According to the report, 53 percent of the nation’s aquifers are losing water at significant rates. This can particularly be seen in the nation’s largest aquifer, the Ogallala, which stretches from the Dakotas to Texas and hydrates seven states.

Approximately 45 percent of Michigan’s population utilizes groundwater in their homes through public community systems and individual private wells. Almost 100 percent of rural and 17 percent of urban Michiganders rely on groundwater.

“Most of our streams in Michigan are fed by groundwater,” said Alan Steinman, the Allen and Helen Hunting research professor at the Annis Water Resources Institute at Grand Valley State University. “If you take away all the rain, in the middle of the summer, whatever baseflow you have under those dry conditions comes from groundwater.”

Just how much groundwater remains under our feet is a guessing game. It is hard to quantify because it lies deep out of sight. Some experts say that just as in any solid business plan, there needs to be consistent data about aquifers and groundwater to understand how much of a product there is and how much will be needed over time.

Steinman said to understand the underground aquifer composition, many may think of science fiction movies like Journey to the Center to the Earth, where explorers in rafts traversed vast underground rivers and cavernous lakes. But that’s not the case.

Steinman said it’s best to visualize Michigan’s Lower Peninsula aquifers as a set of big, asymmetric nesting bowls. The bowls – thicker and deeper in the middle of the state and thinning out at the rims near the Great Lakes and the Detroit River – are made of two geologic media of bedrock or glacial deposits which are thick at the center and thin out towards their rims.

Steinman explained that the center of this system rests in Ingham County. This glacial aquifer is 125 feet deep and fed by the ancient receding glaciers of the last Ice Age. As you get to the edges of the state, the bowl thins out. And the thinner and sandier the layer of that glacial aquifer becomes, the more water it yields.

“If you are trying to pump water from among grains of sand, the particles are large so you can quickly yield a lot of water with a pump,” Steinman explained. “But if you are trying to get that water out of crevices of bedrock, it’s going to be a lot more difficult.”

Below the glacial aquifer is the Marshall Formation aquifer made of bedrock which rests beneath Ottawa and Oakland counties. The lowest bowl, centered around Midland, is comprised of porous sandstone and is the most productive bedrock aquifer in Michigan. It sits under much of the state’s lower peninsula. It has been developed for water supply by municipalities and industry in several areas, especially in the southern portion for agriculture. Here, the thin layers of glacial sediment make for easy drilling and water pumping.

The most acute example of an aquifer running dry in Michigan is in Ottawa County.

Yet the waters of this aquifer, which supplies communities of Ottawa County like Grand Rapids, have been declining for 30 years and is becoming infiltrated with salty deposits from the remnants of an ancient sea.

“If you are putting a lot of demand on this aquifer with a lot of wells, that glacial aquifer is not going to recharge fast enough to meet the demand,” Steinman said. “Therefore, you must start digging wells that are deeper and penetrating that bedrock formation.”

Below the Marshall Formation lies the dried-up remnants of an ancient saltwater ocean. It’s why Michigan is blessed with the largest reserves of rock salt in the country to treat our winter roads. The curse – drill too deeply for water, and those chloride crystals are in danger of adding salt to the fresh groundwater.

“If you are a big municipal water supplier to residents, there are ways, however expensive, to filter out that salinization,” Steinman said. “But if you are a farmer using that water for your crops, if the chloride is high enough, you are going to burn out your crops, especially tender crops like the corn, soy and blueberries we grow in this county. So a new problem is emerging as a double whammy. One is the quantity of the water supply – and the second is the water quality.”

Another area that needs more research is understanding how groundwater interacts with surface waters.

Professor Anthony Kendall is the director of MSU’s Hydrogeology Lab. Its researchers work to understand how human activity impacts the water cycle and includes examining in-state aquifers critical to human and ecological health. Lab researchers recently examined the headwaters of the Au Sable and Manistee River basins in central Michigan to understand temperature, stream flow and groundwater recharge rates by creating a detailed network of stream gaging. Researchers hope that the data will serve as a model throughout the state for land use and fishery management.

Kendall said the interaction between ground and surface waters needs more attention and research. Though groundwater is out of sight, Kendall said all water sources are connected.

“Think of the surface waters we see in our lakes, rivers and streams as a direct expression of what is going on in our aquifers,” Kendall explained. “If the Great Lakes waters are high, the same can be said for the levels of our aquifers. Naturally cool groundwater flows into most of Michigan’s lakes and rivers. Most of the lakes that are populated by residential communities have set legal limits on lake levels. These are controlled and managed by an appointed drain commissioner who may not have expert technical training on lake level management.”

Kendall said Michigan is experiencing new, strange weather patterns because of climate change. There is less snow and this snow melts more rapidly than in previous decades. There are also wetter springs and drier summers with less frequent yet more intense rainfall patterns.

“What worked in the past in terms of lake level management is not going to work in the future,” Kendall said. “My lab is attempting to create the ability to stay on top of these changing conditions. We need to combine more accurate mapping with data to create a picture of the entire landscape. Ideally, we need more water gaging measurements to take place every month. Overall, our groundwater systems have been under-monitored and therefore poorly understood.”

Kendall emphasized that one way to protect groundwater can be as simple as properly maintaining one’s septic system. This has become a big focus of his work. Woefully, Kendall said that Michigan is the last state in the nation to create regulations on septic tank systems. For example, only 11 counties in Michigan require inspecting a septic system as part of a home sale.

“Most of our lake communities are on septic systems,” Kendall said. “When we design these systems, they are meant to remove pathogens and kill bad viruses and other microbes. But they only remove about 30 percent of the phosphorus from the environment and the rest of it leaches out into our groundwater which feeds into our lakes. So, we are putting waste into the beautiful lakes we all enjoy.”

With that said, he understands the exorbitant cost of replacing a septic with a sewer line, which can run into the tens of thousands of dollars. “I’m not saying it’s an easy solution, but lakeside communities must put a bigger focus on properly maintained septic systems. That means getting it thoroughly pumped out annually or every three years, depending on the size of your household.”

Other things one can do to maintain a healthy lake, Kendall instructed, are to manage grass cuttings from floating into the lake, reduce or eliminate lawn fertilizers, and plant vegetative buffers between one’s land and the lakeshore.

“We have known for a long time that there is too much phosphorus getting into our lakes. One of the major victories of the Clean Water Act was that it forced wastewater treatment facilities to modify their operations to remove nitrogen and phosphorus from the water. Beginning in the 1980s, this reduced harmful algal blooms in the Great Lakes and the Saginaw Bay,” Kendall said.

For nearly 25 years, researchers, geologists and state environmental officials have urged state government officials to pay more attention to protecting our aquifers – what some refer to as the sixth Great Lake.

Some geologists interviewed said that Michigan has the most private and municipal wells in the country while also having the poorest documentation of where those wells are in terms of underground geologic formations, their output capacity and their proximity to potential pollutants.

They declare this lack of data hampers all sorts of efforts: from projecting just how much underground water reserves there are to support dependent populations decades into the future to understanding groundwater flow rates around aggregate mining sites.

In 2000, the state, in collaboration with the USGS, created an interactive digital mapping system of the state’s existing wells called Wellogic. New and existing homeowners can call their address, municipality or county to locate the nearest drilled well and its status to estimate the availability of groundwater to drill a new well. But while water well contractors may have been submitting information digitally since 2000, experts say the data retroactively entered is a piecemeal of paper maps created decades ago that have been stored away in dusty filing cabinets of individual municipalities.

Officials at the Michigan Department of the Environment, Great Lakes and Energy (EGLE) will install a well water gage in areas where contaminants are suspected.

However, researchers are critical of this reactive and not proactive approach. They claim that the state lacks gages and data collection points in unremarkable areas to understand how groundwater levels fluctuate over time. A lack of consistency has led to groundwater systems being poorly understood and managed compared to the study of surface water systems.

In August 2003, the state legislature enacted Public Act (PA)148, which required Michigan to create and maintain a groundwater map and did so with a collaborative project between the Institute of Water Resources (IWR) at Michigan State University (MSU) and state environmental regulators. The state viewed this as the most efficient way to inventory the quality and the conditions of the subterranean waters and solve future groundwater disputes and conflicts that may lie ahead.

Since 2005, the state has also managed a database of aquifer maps using the Geographic Information System (GIS) developed to express the uncertainty or statistical significance of the data. The data was intended to display seasonal and long-term variability in groundwater levels.

The first law protecting the over-pumping of aquifers in Michigan went into effect with the 2008 passage of the Great Lakes Water Compact, according to Nicholas Schroeck, associate professor of law at the University of Detroit – Mercy. This marked the creation of Michigan’s Water Withdrawal Assessment Program, which was designed to prevent severe damage to lakes and streams because of siphoning off of large amounts of water from surface and groundwater sources.

According to EGLE, the Water Withdrawal Assessment Program is intended for use before installing a new or increased large quantity withdrawal to determine the potential impact on nearby water resources. Use of the Water Withdrawal Assessment Tool is required before installation of any new or increased large quantity withdrawal.

In accordance with Part 327 of the state’s Natural Resources Environmental Protection Act, a new or increased large quantity withdrawal over 100,000 gallons per day up to two million gallons per day must be authorized by the state with an annual $200 permit. Very large withdrawals of two million gallons per day, if permitted, are subject to a permit application fee of $2,000.

“Before this was codified into state law, there was not a lot of regulation for groundwater pumping in the state of Michigan,” explained Schroeck. “Typically, the way property law works, if you own a piece of property in the state, the groundwater that flows below is part of your ownership. That’s the common law rule, and we’ve been practicing this since we were under the rule of the British.”

He continued: “That was the first real permitting or licensing that we had for groundwater withdrawals in Michigan. Here, agriculture is one of the biggest users of groundwater in the state. But before 2008, we didn’t have great data on how much groundwater (for agriculture) was being used.”

Schroeck said that EGLE grants permits for the majority of the applicants, be they farmers or businesses, unless they are applying to withdraw groundwater from an aquifer where there are known stressors.

“There are some limitations on groundwater pumping in the western part of the state towards Grand Rapids, and there has also been stress put on aquifers primarily from agricultural use,” Shoreck said.

When we think of water depletion of aquifers, the parched Southwest or the Great Plains come to mind. An area of seven states stretching from the Dakotas and Wyoming down to Texas is hydrated by the shrinking Ogallala Aquifer. According to Scientific American, the Ogallala Aquifer is being depleted at an annual volume equivalent to 18 Colorado Rivers.

Ottawa County, a fast-growing region along the shores of Lake Michigan, is at risk of its aquifer running dry in the coming decades.

According to the U.S. Census, the population in the county from 1960-2040 is expected to quadruple. Ottawa County commissioned Michigan State University in 2012 to investigate groundwater issues raised by locals, well drillers and farmers.

The main reason for the aquifer’s depletion is a geologic one. As Steinman at the Annis Water Resources Institute at Grand Valley State University previously explained, part of the geologic makeup of Ottawa County is a thick layer of glacial clay which drastically slows rainwater or snowmelt from replenishing the aquifer.

Steinman served on the executive committee for the 2019 Ottawa County Groundwater Sustainability Initiative, which mapped out a multi-pronged education, outreach, and conservation plan for the community to teach about possible solutions to conserve and preserve its water supply. Steinman was the lead author of Addressing Groundwater Challenges In Michigan As A Template For The Great Lakes, published in the 2022 Journal of Sustainability. The study was a compilation of research from leading state academics, researchers, and environmental organizations who gave caution about the critical but understudied and underfunded nature of groundwater as a natural resource.

With a focus on the plight of Ottawa County, the study stated that over the last 40 years, because of continued groundwater withdrawals from the Marshall Aquifer, water levels in Ottawa County dropped more than 13 meters, with an additional six-meter drop likely within the next 15 years if withdrawal rates continue at the current rate.

In those areas where freshwater recharge can infiltrate the bedrock aquifer system, subsurface drainage systems, draining excess water away from agricultural areas and into drainage ditches, may limit the aquifer recharge.

The study recommends an enhancement of the capture and reuse of water runoff to divert it back into the aquifer, updating drainage systems and updating statewide maps of groundwater recharge potential.

In comparison, the waters of Oakland County’s aquifers are plentiful but not without peril.

In the early 2000s, Oakland County commissioned the USGS to conduct a mapping survey of the geological conditions of the county’s underwater reserves. The study examined how land cover changes between 1970-2003 impacted the county’s topography and stream flow.

In 1972, about 850,000 people lived in Oakland County and used about 100 million gallons of water per day. In 2000, about 1.2 million people lived in Oakland County and used 168 million gallons of water per day. About 75 percent of that water was supplied from the Great Lakes by the Detroit Water and Sewerage Department (DWSD), now renamed the Great Lakes Water Authority (GLWA).

By 2000, 240,000 Oakland County residents relied on domestic wells which pumped out 21 million gallons daily. Over the next 20 years, the county’s population is expected to grow by an additional 200,000, mainly in the northern and western parts of the county that use groundwater, to the tune of an extra 20 million gallons daily. Municipalities in this area, like Highland Township, White Lake, Waterford, Milford, and other areas in the county, rely on groundwater for their water supply.

When residents pump water from the aquifers, that wastewater is sent not back to the aquifer but to a wastewater treatment plant and then back to our surface waters. While a household using a well and a septic system returns approximately 90 percent of the water pumped from the well back into the ground, residents connected to wastewater treatment plants represent a 100 percent loss of water to the aquifer system, said the report.

In 2000, public groundwater suppliers delivered approximately 22.87 million gallons daily to 169,000 residents, and an additional 240,000 residents used private wells.

Despite the population growth, surface and groundwater quantity was not negatively impacted. There were few areas in the county supplied by a mixture of ground and piped-in water, and there were steadily decreasing levels of water in some streams between 1970 and 2003. Compared to a study from 1972, the quality of the water by the early 2000s had improved with decreased levels of nitrogen, phosphorus and sulfate.

Howard Reeves, a USGS research hydrologist and the watershed modeling team, explained that with Oakland County’s varying topography, finding the sweet spot for groundwater takes lots of skill.

“All of Oakland County rests on a mantle layer of glacially deposited material, so the productivity of an aquifer to provide drinking water varies widely,” explained Reeves.

Reviewing the Oakland County report, Reeves said the glacial mantle between the earth’s surface and the aquifer can range from hundreds of feet to only a few feet.

“Most wells in Oakland County are located on this glacial area which is comprised of sand, silt and clay,” explained Reeves. “The most productive wells are in areas where there is lots of gravel, which allows for more water to be captured. Home buyers building new construction can take for granted that there is access to water. They think it is easily accessible and they can drop a well anywhere and reach water. Though our topography is not like the hard granite of New England, where drillers must work extra hard to access water, drilling for water here does take skill. Fortunately, our state’s drillers know what they are doing.”

Reeves said Wellogic provides new and existing homeowners a good understanding of where neighbors found water and how far below they had to drill to reach it. Still, the glacial mantle makes conditions very variable.

“In some instances, you have a neighbor with a 120-foot well and they have great quality water flow and quality, and then a few plots down they had to drill down to the top of the bedrock layer and their water may not taste as good,” he noted.

MSU Professor Emeritus David Lusch, one of the foremost experts on aquifers and aquifer mapping in the state, said the 2005 study disproved some misconceptions that aquifers in Oakland County could be running low. With climate change, Michigan is experiencing wetter springs and summers. Lusch said the real-time online map created by the USGS on wells throughout the state indicated that this spring the 33 wells monitored by the USGS in the county are showing normal or above aquifer levels.

“One might think that with the persistent urbanization of Oakland County over the last 30 years, there would be a noticeable depletion of the aquifers and it would be quite noticeable,” Lusch said. “But the data just doesn’t support that. And when we try to figure out how this can be – that we have more users drawing from the same water resource – we don’t see a declining signal in water levels.”

That is not to say that there will not be supply shortages in the future, Lusch cautioned. As time marches on, Michigan will endure inconsistent rainfall. Extended periods of dry, hot weather will be punctuated with short intense bouts of heavy rainfall. And like a dry sponge, arid ground cannot quickly soak up these downfalls and direct water back to the aquifers. This is especially true with Oakland County’s heavy clay soils and the fact that urbanization has covered up much of the land with impervious surfaces, said Lusch.

Lusch continued: “When our heavy soil and mostly impervious urban infrastructure encounters these heavy rain events, the soil just cannot absorb all that water. Our urban infrastructure blocks the water from taking its natural path, which is sinking back into the aquifers through layers of the earth. So even though we may be seeing more rain, instead of generating aquifer recharge, we end up with local flooding. If you have forested land or open green spaces, it sends the water back into the aquifers.”

Lusch said he would recommend the state legislature pay closer attention to aquifers and put more money in the budget to pay for further data collection and monitoring by the USGS.

“That’s another part of the ignorance factor in not appropriately providing funding for that because the USGS doesn’t do this out of the goodness of their hearts, either. They have to have a cooperative financial arrangement with the state of Michigan.”

Lusch said the cost of a comprehensive study, such as the kind that Oakland County commissioned the USGS to do back in 2005, costs between $30-40,000.

“The USGS created the (2005) study at the invitation of Oakland County,” mused Lusch. “They do not do these studies out of the goodness of their hearts, and it does not help that the USGS has also had their funding cut at the federal level.”

In his many talks, Lusch describes Oakland County’s inland lakes as groundwater “without a top on it.”

“If an owner of a lake home can think of it that way, it might make them feel more connected and responsible for that water that rests right outside their doorstep,” said Lusch. “In Oakland County, tapping into the groundwater happened quite rapidly, and this is why we have so many inland lakes. Homeowners must ask themselves: When was the last time they took care of their septic system? When did they last pay attention to how much fertilizer and chemicals they applied to their lawn? All those chemicals will leach right into the waters of your lake.”

Mark Hansell, Oakland County’s chief of Environmental Health Services said that those in Oakland County who receive their water from municipal wells have their water tested and treated for harmful bacteria and contaminants just as customers who receive water from the Great Lakes Water Authority. Hansell said that homeowners on private wells are responsible for testing their water, and guidelines and costs for well inspection can be found on the Oakland County Health and Human Services well program website.

The Michigan Department of Health and Human Services (MDHHS) recommends routine testing for coliform bacteria and E. coli or nitrate annually and testing for arsenic, copper and lead every three to five years. Extra tests for the above should occur any time a household member is pregnant, if there are infants and young children at home, flooding near the well, or changes in the water’s taste, color or odor.

New residential and commercial construction in Oakland County not served by the Great Lakes Water Authority must apply for a permit. Before the county permits a new well, Hansell said the county must assure there are no areas of contamination on the land that would pose a risk to the groundwater and human health based on data they glean from reports from EGLE as well as the 2005 USGS study for Oakland County. Any permitted wells must be bored by a state-certified well driller under the Weld Construction Code in the state’s Code of Public Health. During a well’s drilling, the MDHHS will make a few visits to ensure all operations and design of the well are up to code.

“There is a lot of due diligence before we even visit a site applying for a well permit,” Hansell explained. “Once we review existing records and mapping of the area, we’ll visit the site to look for other possible sources of contamination. If there is a septic system in your yard or a neighbor’s yard, we want to make sure it is being properly maintained to protect that well, the aquifer, and ultimately, your health.”

Lusch said that with all the work and studies he has facilitated over the decades, what is most important is that government officials become more educated about managing groundwater resources.

“In my 30 years of research, I find this area is woefully lacking. Most are poorly informed or ignorant about how to protect groundwater,” he noted.

The Michigan state legislature approved in its 2023-2024 budget more money for the study of aquifers. EGLE was allocated in the budget a one-time infusion of $23.8 million to hire two full-time employees who will manage a new research project called the Groundwater Data Collection initiative.

EGLE officials defer to the USGS for having more comprehensive data resources on the state’s groundwater supplies and conditions. EGLE spokesperson Hugh McDiarmid said that currently, the state does not perform comprehensive mapping and monitoring of specific aquifers unless there is evidence of contamination. The Michigan Geological Survey is at the beginning stages of mapping programs for aquifers with EGLE organizing the data, but this project will not bear any fruit for another two years, McDiarmid said.

Despite some late advances, John Yellich, director of the Michigan Geological Survey based at Western Michigan University, said that geologically speaking, Michigan is the most poorly mapped state in the country. To improve this, in the last two state budget cycles, the Michigan Geological Survey received annual funding, as well as a grant through the Department of Natural Resources, for five years at $1 million per year to map aggregates in Michigan. Yellich said all this mapping ties back to understanding our aquifers.

“I have had decades of experience working as a geologist,” Yellich said. “I have worked on groundwater cleanup and hazardous waste cleanup sites in 20 states. When I took this position in 2013, within three months I concluded that Michigan was the most disappointing state I have ever worked in in terms of not having any data on its groundwater.”

Yellich criticized the lack of training the state’s drillers had in properly and consistently entering data into the Water Withdrawal Assessment Tool and Wellogic and began a training program to improve accuracy.

Yellich said it is important to properly map Michigan’s underground terrain in terms of where our legacy pollution lies – elements like coal ash, aggregate mining, industrial sites and forever chemical deposits – about where stores of underground water reserves exist.

“Back in the 1970s and 1980s, Michigan did not think about where we were allowing industry and manufacturing to operate in terms of how close they were to groundwater sources,” Yellich said. “These legacy industries still impact our shallow aquifers. That is why our mapping program is important. The maps will show the locations of shallow sand and gravel deposits. That way, cities can better determine where to allow industries to operate. This is because industries carry the potential for spills of contaminants into our groundwater. This is a mapping system that is only now being developed. It could have been useful decades ago.”