Well Water Quality Viewe​r: Private Well Data for Wisconsin​


 WI Well Water Quality Interactive Viewer


The WI Well Water Quality Interactive Viewer was created as an educational tool to help people better understand Wisconsin's groundwater resources. Communities or​​​​ individuals have used it to:

  • See what is known about general well water quality in Wisconsin.
  • Compare water quality in different areas.
  • Raise awareness of local groundwater quality issues.
  • Promote testing and outreach efforts.
  • Encourage well testing in areas where little data exists.

The viewer relies on voluntarily submitted well water samples fro​m homeowners an​d other well water data collected by state agencies over the past 25 years. This includes 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 La Crosse County Health Dept.

The WI Well Water Viewer does not represent well water quality information for all known private wells. This information is not intended to be a substitute for well water testing and the viewer 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.

The compilation of data was assisted by a grant through the Environmental Public Health Tracking Program through the WI Department of Health Services.


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 40 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 15 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 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 visit the following link: Tests for Drinking Water from Private Wells

Always have your water tested at a certified laboratory:

 Link: 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. Well data is not publicly available to a specific property. 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.

A well can be significant to the overall value of a rural property.  Knowing what condition the well is in and having a current water quality test can be important when finalizing the sale of a rural property with a well.  Water quality can also change over time and its always best to get a current evaluation of water quality.  Sampling the well prior to purchasing the property is the only way to know for sure the current water quality.

The viewer can be useful in providing some information on what water quality is like in the area or what additional parameters might be worth testing for. 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.

​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.

Information on trends in nitrate-nitrogen in Wisconsin's public water systems can be found here:Nitrate in Wisconsin's Public Water Systems​

A few counties have initiated projects to investigate well water quality trends in their communities: ​​Community Trend Monitoring Projects

​Other h​istorical statewide groundwater quality inventories:

Wisconsin Groundwater Quality - DATCP, 2023​

Wisconsin Groundwater Quality - DATCP, 2017

Wisconsin Groundwater Quality - DATCP, 2008

Wisconsin Groundwater Quality - DATCP, 2002