GCC Report to the Legislature Groundwater quality
Groundwater contamination from human and natural causes occurs across Wisconsin. This is of particular concern for the 70% of Wisconsin residents who obtain their drinking water from groundwater. Other groups that are affected by groundwater quality include farmers who rely on groundwater for irrigation, industrial and commercial users and the environment.
Trends in groundwater quality in Wisconsin are mixed both increases and decreases in groundwater quality are observed. Information about the distribution of naturallyoccurring metals is improving. Continued attention is needed to the occurrence of increasing and emerging contaminants, including nitrates, bacteria and viruses.
Common contaminants usually acute health effects
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.
Nitrate is Wisconsin's most widespread groundwater contaminant. Most nitrate in groundwater (90%) is due to agricultural inputs.
Common contaminants usually chronic health effects
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.
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.
Radionuclides are radioactive atoms. It is possible for radionuclides to be manmade but they also occur naturally in rock formations and are released to groundwater over millions of years by geochemical reactions.
Volatile Organic Compounds
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.
Less common contaminants
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.
- UW-Stevens Point interactive map: WI Well Water Quality Viewer
- USGS interactive map: A Decadal Look at Groundwater Quality
- DNR water quality and contamination in private wells
- DHS overview of water quality issues
- WGNHS overview of drinking water quality
- Peer-reviewed overview of groundwater issues in Wisconsin (Luczaj and Masarik, 2015)