Well Water Quality Viewer: Private Well Data for Wisconsin

 WI Well Water Quality Interactive Viewer

Homeowners and local units of government can use this tool to:

  • See what we know about general well water quality in Wisconsin.
  • Compare water quality in your area to nearby towns or counties.
  • Raise awareness of local groundwater quality issues.
  • Promote testing and outreach efforts.
  • Encourage well testing in areas where little data exists.
  • Highlight the importance of testing well water on a regular basis.​

Disclaimer: The viewer summarizes private well water quality data from the Center for Watershed Science and Education,the WI Dept. of Ag, Trade and Consumer Protection, and the WI Department of Natural Resources Groundwater Retrieval Network, Eau Claire County Health Dept and LaCrosse County Health Dept. It is not considered a scientific study and does not represent well water quality information for all known private wells. The compilation of data was assisted by a grant through the Environmental Public Health Tracking Program through the WI Department of Health Services.

This information is not intended to be a substitute for well water testing and does not provide site specific information for an individual well or property. The Center for Watershed Science and Education is not responsible for misuse or misinterpretation of the data.

Direct questions on using and interpreting this information to Kevin Masarik.


Interactive Well Water Quality Viewer 1.0 created by David Mechenich, Center for Watershed Science and Education

 Wisconsin Well Water 101


Learn about groundwater and your well water system with this interactive guide

Use this guide to:

  • Learn the basics of groundwater flow
  • Discover the major aquifers and watersheds of Wisconsin
  • Interpret your water test results
  • Find ways to improve your water quality
  • Learn more about the construction of your well


The WI Well Water Quality Interactive Viewer was created as an educational tool to help people better understand Wisconsin's groundwater resources that many of us rely on for our drinking water.

Nearly 900,000 households rely on private wells as their primary water supply. Homeowners with private wells are encouraged to have their well tested on a regular basis to determine the safety of the water supply for purposes such as drinking and cooking. While testing is the only way to determine the types and amount of contaminants in a well water system, homeowners and local officials often want to know more about water quality issues in their community.

​How does the viewer work?

The viewer relies mostly on voluntarily submitted well water samples from homeowners and other well water data collected by state agencies over the past 25 years. It would not have been made possible without the many well owners who took the initiative to have their wells tested.

Because groundwater quality can often be very site specific for certain contaminants, many water samples are required to get a sense of groundwater quality at a county or watershed scale. By combining all of this data together we are able to look at averages or the number of samples that exceed drinking water standards to better understand private well water quality across the state.

  • Select a county, township or section to view water quality summaries at different scales.
  • Select from one of 14 different water quality parameters.
  • Areas that are blank show areas where insufficient well water data exists to summarize well water quality for that area. But you can use the groundwater quality summary statistics tool to see the number of samples that exist in a particular county, township, section or user defined area.
  • Map colors can be adjusted for those that have trouble viewing certain colors or if you are printing maps on a non-color printer.

​The viewer does not show any problems where I live. Should I still have my water tested?


Yes, absolutely. The viewer is not a replacement for testing your well. Well water quality is often very site or system specific. Every well should be tested for certain things depending on where you live and the types of land-use activities  around your well.

Certain tests like bacteria are recommended to be tested for on an annual basis or anytime water changes color, taste or odor. Water quality can also change - so testing for things like nitrate on a regular basis can be used to track changes in water quality over time.

For more information on important tests to perform on a private well please download the brochure:

Tests for Drinking Water from Private Wells

Always have your water tested at a certified laboratory:

Laboratories certified to test for bacteria
Search laboratories certified for other contaminants

​I am purchasing a new home, can the viewer locate water quality results for a particular well or property?

No. Anytime you invest in a new home or property with a private well we strongly encourage you to have it inspected by a certified well inspector and have it sampled for some basic water quality concerns at that time.

Many of the results displayed in the viewer are voluntarily submitted well water samples and we cannot verify the results of any one individual test result. Individual test results have the potential to misrepresent water quality, both good and bad. For example, some homeowners submit samples that have passed through water treatment devices that may make water quality appear better than it actual is. A past positive bacteria test may no longer be an issue if an old well cap was replaced. Lastly, water quality can change over time. Many of the samples displayed in the viewer may be years or even decades old and not representative of the well water at the time of sale. Sampling the well prior to purchasing the property is the only way to know for sure the current water quality.

The value of the water quality viewer is in the amount of data displayed. It does a good job of showing areas where water quality has been degraded or is more likely to exceed certain drinking water standards. It relies on the law of averages and requires large numbers of samples in order to characterize water quality for a county or town. The smaller the number of samples the less representative the information will be of water quality in an area. The viewer is not a replacement for a water test and should not be used for site specific planning purposes.

​Is groundwater quality getting better or worse?

The viewer is good at identifying areas where water quality issues exist. It is not designed to look at trends in water quality over time.

Answering whether water quality is getting better or worse requires baseline data as a starting point and regular monitoring of wells into the future. This viewer is a good start for communities to view baseline data and identify areas where more data is needed. It can also help communities focus future water quality testing efforts in areas where problems exist.

If the viewer is successful in encouraging private well owners to perform routine well water testing then in the future we will have a better chance of answering whether groundwater quality is getting better or worse.

Historical statewide groundwater quality inventories:

Wisconsin Groundwater Quality - DATCP, 2008

Wisconsin Groundwater Quality - DATCP, 2002

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