Groundwater Protection

Groundwater fills up pores and cracks in soil and rocks, and is present underneath hills, lakes and other ecosystems (DNR). Groundwater protection is vital to states like Wisconsin, where two-thirds of the people draw their drinking water from underground aquifers (DHS). Groundwater can also play a role in crop and livestock production, manufacturing, and commerce (DNR). Unfortunately, these waters face threats:

1. Toxic Contamination --- While the ground serves as a filter, it doesn't catch everything (USGS). In Wisconsin, groundwater contaminants include E. coli and other pathogens, nitrate, arsenic, pesticides, radionuclides, and volatile organic compounds (VOCs), a group of chemicals that includes gasoline and industrial solvents. (Wisconsin Groundwater Coordinating Council (GCC) 2022 Report to the Legislature). Learn more about drinking water contamination here.

2. Excessive Withdrawals. Groundwater levels can drop due to pumping water without giving sufficient time for aquifers to recharge naturally (GCC 2022; USGS). Groundwater depletion can lead to wells drying up, less water in springs and lakes, worse water quality, and land subsidence (USGS). Learn more about water conservation in Wisconsin here.


As of the GCC's 2022 Report, the Wisconsin Department of Natural Resources hadn't been allowed to make revisions or additions to groundwater standards for over 10 years. The GCC recommended setting new and revised health-based groundwater standard recommendations, implementing practices that protect groundwater from nitrate and other agricultural contaminants, and addressing public health and environmental concerns regarding PFAS.

Consult the DNR's website for new information on the agency's work. You can check the status of proposed DNR rules here, and check here for opportunities for public input. For one, at the time of this article, the DNR is in the process of setting standards for certain per- and polyfluoroalkyl substances (PFAS) (DNR). We encourage you to make your voice heard.

Fractured Limestone in Northweast Wisconsin

Wisconsin's Door County has rugged shorelines, mild climate, abundant natural resources, and a small-town feel that together have made it a popular tourist destination in the Midwest. Beneath it lies the Silurian dolomite aquifer, a major water supply for the U.S. and Canadian Great Lakes region (Borchardt et al., 2021).

Door County's charm, and its groundwater problems, are directly related to its unique geology. On the western side of the county the Silurian escarpment forms high cliffs along the Green Bay shoreline, only a few miles to the east the land meets Lake Michigan with sandy beaches and diverse wetlands. In some places, especially northern counties, fractured dolomite is exposed at the surface (WGNHS).The dolomite contains both near- horizontal and vertical fractures (WGNHS). These fractures are extensive, and the vertical fractures are easily visible from the air. Cracks and fractures allow groundwater and pollutants to move rapidly through the aquifer (WGNHS). Areas of thin cover of glacial materials are especially vulnerable for contamination of the eastern dolomite aquifer.

karst diagram
WGNHS, sourced from runkel and others, 2003.

water pump

Groundwater Contamination in Door County

Groundwater quality problems have plagued Door County for many years. Beginning in October 2000 and ending in May 2001, the Department of Agriculture, Trade and Consumer Protection (DATCP) a nd the University of Wisconsin-Extension tested samples from rural private drinking water wells to determine the impact of agricultural pesticides on groundwater resources. Results from the study showed over 35 percent of wells tested contained detectable levels of commonly used herbicides or their metabolites (compounds created when herbicides and other chemicals deteriorate in soils).

One study estimated that about 1,300 wells ( 27%) during the study period didn't meet the EPA's public health goals for safe drinking water. Nearby agricultural land use was one factor associated with well contamination (MEA/EPA). In February 2022, Midwest Environmental Advocates urged the EPA to “step in and order immediate, enforceable actions to provide clean drinking water and prevent further groundwater pollution.” MEA said that Kewaunee County residents needed the DNR to enforce the law, and that residents needed clean bottled water in the interim (MEA/EPA).

Take Action!

- Subscribe to CWAC's Weekly Update to receive opportunities to help protect the environment every week. Email and ask us to place you on the Weekly Update mailing list.

- Make your voice heard:

- If you see evidence of an agricultural operation has caused water pollution through manure, you can report your concern to the DNR. If you would like to remain anonymous, you can use the DNR Tip Hotline at 1-800-TIP-WDNR (1-800-847-9367) or cell #367 (DNR).

- Visit the Take Action section of our Nonpoint Source Pollution article for more ways to take action.

More Resources

- Groundwater (DNR)

- Drinking water, wells, and groundwater publications (DNR)

- Wisconsin Water Withdrawals (DNR)

© Clean Water Action Council

P.O. Box 9144

Green Bay, WI 54308

(920) 421-8885

Office location:
A307 MAC Hall, UW-Green Bay
2420 Nicolet Drive
Green Bay, WI 54311