Southwest Wisconsin has fractured bedrock beneath generally thin soils, putting groundwater at risk for contamination.
The purpose of this study is to improve our understanding of groundwater quality in southwest Wisconsin and to better understand how local hydrogeology and well construction characteristics affect groundwater quality.
- Evaluate private well contamination using indicator bacteria (total coliform and E. coli) and nitrate;
- Assess well construction and geological characteristics (e.g., well age, depth to bedrock) that affect total coliform and nitrate contamination; and
- Identify the source of contamination (people, cows, or pigs) in a subset of wells that tested positive for total coliform and nitrate.
Frequently asked questions
Are 91% of private wells in rural southwest Wisconsin really polluted?
No. This is a confusing misconception. The percentage of affected wells is lower. In our first round of sampling, 42% of wells were contaminated. In the second sampling event, 27% of wells were affected.
Later resampling targeted wells known to be contaminated in order to try to identify the source(s) of that contamination.
Is more sampling planned?
Yes. Our sampling to identify the source(s) of contamination is planned to be repeated in all four seasons. Results of the resampling events are as follows:
- Spring: 32 of 35 private wells, or 91%, tested had contamination of fecal origin (human, cattle, and swine).
- Summer: 25 of 34 private wells, or 73%, tested had contamination of fecal origin (human, cattle, and swine).
Should I have my well tested if it is not part of this study?
Private drinking water wells should be tested annually or more frequently if you notice a change in the water or in nearby land use. More information is listed below in “Resources for private well owners.”
Resources for private well owners
- Information for private well owners (Wisconsin Department of Natural Resources)
- Identify your water’s symptoms (Wisconsin Department of Natural Resources)
- Homeowner well water testing (University of Wisconsin–Stevens Point)
- Well water quality viewer—interactive map (University of Wisconsin–Stevens Point)
More about the study
- News article (Dec. 4, 2019): More testing confirms southwestern Wisconsin wells contaminated with fecal matter
- News article (Dec. 3, 2019): Study ties well contamination in southwestern Wisconsin to human and livestock sources
- Press release (Dec. 2, 2019): SWIGG study update – identifying sources of fecal contamination in private wells in Lafayette, Grant, and Iowa Counties (part 2) (PDF)
- News article (Aug. 7, 2019): New SWIGG study results raise serious concerns (SWNews4U.com)
- Press release (Aug. 1, 2019): SWIGG study update – identifying sources of fecal contamination in private wells in Lafayette, Grant, and Iowa Counties (part 1)
- Handout for SWIGG residents (Aug. 1, 2019): Update on the Southwest Wisconsin Groundwater and Geology Study (PDF)
- Extension Iowa County website: https://iowa.uwex.edu/community-development/swigg/
- Press release (June 6, 2019): SWIGG study completes the first phase
- Video (May 24, 2019): Keeping Wisconsin Water Clean (Wisconsin Public Television—Here & Now)
- News article (Jan. 2, 2019): Hazardous drinking water found in 42% of southwest Wisconsin wells (Wisconsin State Journal)
- Press release (Sept. 24, 2018): Well water study announced for southwestern Wisconsin
For more details about this project, please contact