Michigan is called the Great Lakes state but is a poor steward of the sixth Great Lake, the water lying beneath Michigan’s ground. During National Groundwater Awareness Week March 10-16, FLOW is calling for state-level reforms to strengthen protection of Michigan’s groundwater.
The Invisible Resource
Groundwater is an immense and invisible resource. 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 a giant asset and life-giving resource that fills wells, grows crops, fuels industry, and replenishes the Great Lakes.
This week, we feature content directly related to this resource. FLOW has been investigating Michigan groundwater policies and problems for more than a year. In September 2018, we released a report, The Sixth Great Lake: The Emergency Threatening Michigan’s Overlooked Groundwater Resource. Our concern and communication continues.
Our content to be released throughout Groundwater Awareness Week includes an inspiring video narrated by poet and author Anne-Marie Oomen; two podcasts developed by writer and broadcast professional Sally Eisele; blog posts by FLOW experts shining a spotlight on PFAS and other groundwater pollution problems and protective solutions; and a fact sheet summing it all up.
In addition, FLOW is developing a groundwater map for release later this spring making it easy for you to learn about the resource across Michigan and in your region of the state.
Why Is Groundwater Important?
Michigan has more private drinking water wells than any other state. About 45% of the state’s population depends on groundwater as its drinking water source. Michigan industries withdraw 64 million gallons of groundwater daily from on-site wells. Over 260 million gallons of groundwater are withdrawn daily in Michigan for irrigation. 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. Of the 50 states, only Michigan lacks a statewide law protecting groundwater from septic systems – and there are an estimated 130,000 leaking septic systems within Michigan’s borders. Other major threats include an estimated 6,000 contamination sites for which no private or public funding is available and widespread nitrate contamination from agricultural practices.
What Is Groundwater?
The hydrologic cycle governs water movement. Surface water is heated by the sun and evaporates into the atmosphere, forming clouds. These clouds condense and precipitation falls back to Earth as rain, snow, sleet, or hail. Water will then either return to a surface body of water or seep into the soil and move through the crust as groundwater.
Some may envision groundwater as an underground river or lake, but groundwater is held in tiny pore spaces in the rock and soil. After water is absorbed into the ground, gravity pulls the water down through the unsaturated zone. This area of the Earth’s crust is where tiny gaps between sediment grains, called pore spaces, are filled with either air or water. Water here can be trapped and used by plant roots or percolate downward into the saturated zone, where water exclusively fills the pore spaces.
The division between the unsaturated and saturated zone is called the water table. This two-dimensional plane often follows the contours of the surface above, moving seasonally based on precipitation events.
Groundwater in the saturated zone moves both vertically and horizontally, flowing towards a lower elevation discharge point like a stream or a lake. These surface bodies of water often rely on groundwater sources, in addition to precipitation, to recharge their water levels. After re-entering a surface body of water, the water continues through the hydrologic cycle.
As groundwater moves through the surface of the Earth, it often travels through an aquifer. Aquifers are underground formations that contain water at high enough concentrations that we can sustainably pump.
The two types of aquifers are called confined and unconfined aquifers, differing in whether or not there is an impermeable layer between the surface and the aquifer or not. Both types of aquifer can be used as a freshwater source, but unconfined aquifers are much more easily affected by surface actions and contamination and are more susceptible to pollution and degradation.
Almost all groundwater will discharge into surface water, unless it is extracted first. As a result, contaminated groundwater can degrade lakes, streams, and the Great Lakes.