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GCC Report to the Legislature Groundwater quality

Groundwater pollution from human activities and natural sources occurs across Wisconsin. This is of particular concern for the 70% of Wisconsin residents who obtain their drinking water from groundwater. Other groups concerned about groundwater quality include farmers who rely on safe groundwater for crop and livestock production and business owners who rely on groundwater for manufacturing and commerce. Lakes, rivers and streams are fed by groundwater. Fish and wildlife can't thrive when groundwater contaminants impact the surface water they are dependent on.

We are learning more about groundwater quality in Wisconsin. Collecting information about the occurrence of different substances found in groundwater and their impacts to human and environmental health are ongoing subjects of research.

Common contaminants — usually acute health effects


photo of pathogens

Escherichia coli. Photo credit: National Institute of Allergy
and Infectious Disease.

Pathogens are organisms or other agents that can cause disease, including microorganisms such as bacteria, viruses and protozoa that can cause waterborne disease. Pathogens in groundwater can often be traced to human or animal fecal wastes.

» Read more.


Photo of a tractor in field

Photo credit: DNR.

Nitrate is Wisconsin's most widespread groundwater contaminant. Most nitrate in groundwater (90%) is due to agricultural inputs.

» Read more.

Common contaminants — usually chronic health effects

Arsenic and other Naturally-Occurring Elements

Photo of pyrite

Pyrite. Photo credit: JJ Harrison.

Arsenic occurs naturally in soil and rock, typically bound to other minerals such as pyrite (pictured). Under certain environmental conditions, arsenic can dissolve and be transported in groundwater. Other examples of natural contamination in Wisconsin are radium in southeastern Wisconsin, chromium in Dane County and strontium.

» Read more.


Photo of a plane spreading pesticides

Photo credit: DATCP.

Pesticides are a broad class of substances designed to kill, repel or otherwise disrupt living things that are considered pests. Normal field applications, spills, misuse or improper storage and disposal can all lead to pesticide contamination in groundwater.

» Read more.


Photo of radioactive symbol

Photo credit: Pixabay.

Radionuclides are radioactive atoms. It is possible for radionuclides to be man–made but they also occur naturally in rock formations and are released to groundwater over millions of years by geochemical reactions.

» Read more.

Volatile Organic Compounds

Photo of chemical container

Photo credit: DNR.

Volatile Organic Compounds (VOCs) are a group of common industrial and household chemicals that evaporate or volatilize when exposed to air. Improper handling or disposal of VOCs is often the reason why they occur in groundwater.

» Read more.

Emerging contaminants

Emerging contaminants

Photo of prescription pill bottle

Photo credit: US Department of Defense

Emerging contaminants are compounds that are increasingly being detected in groundwater and may have harmful human health or environmental impacts. Many, but not all, of these emerging contaminants enter the groundwater from wastewater or solid waste sources.

» Read more.

Additional Resources

Last revised: Thursday August 29 2019