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.
Project objectives
- 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?
No. We have now completed four rounds of sampling. The following results show the percentage and number of resampled wells that tested positive for contamination of fecal origin from humans, cattle, and/or swine:
- Spring 2019: Contamination found in 32 of 35 private wells (91%)
- Summer 2019: Contamination found in 25 of 34 private wells (73%)
- Fall 2019: Contamination found in 27 of 34 private wells (79%)
- Spring 2020: Contamination found in 21 of 35 private wells (60%)
What happens next?
Team researchers will continue to analyze the data looking for correlations between water quality, geology, and well construction. The study’s final report should be complete in 2021.
Should I have my well tested if it was 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
More about the study
Background information
- Extension Iowa County website: https://iowa.uwex.edu/community-development/swigg/
- Press release (Sept. 24, 2018): Well water study announced for southwestern Wisconsin
- News article (Jan. 2, 2019): Hazardous drinking water found in 42% of southwest Wisconsin wells (Wisconsin State Journal)
- Video (May 24, 2019): Keeping Wisconsin Water Clean (Wisconsin Public Television—Here & Now)
- Press release (June 6, 2019): SWIGG study completes the first phase
- Handout for area residents (Aug. 1, 2019): Update on the Southwest Wisconsin Groundwater and Geology Study (PDF)
Spring 2019 results
- Press release (Aug. 1, 2019): SWIGG study update – identifying sources of fecal contamination in private wells in Lafayette, Grant, and Iowa Counties (part 1)
- News article (Aug. 7, 2019): New SWIGG study results raise serious concerns (SWNews4U.com)
Summer 2019 results
- 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 (Dec. 3, 2019): Study ties well contamination in southwestern Wisconsin to human and livestock sources (Milwaukee Journal Sentinel)
- News article (Dec. 4, 2019): More testing confirms southwestern Wisconsin wells contaminated with fecal matter (Wisconsin State Journal)
Fall 2019 results
- Press release (April 15, 2020): SWIGG study update – identifying sources of fecal contamination in private wells in Lafayette, Grant, and Iowa Counties (PDF)
- News article (April 19, 2020) Study of southwest Wisconsin well water continues to indicate contamination (Wisconsin State Journal)
- News article (April 19, 2020) Study identifies sources of fecal contamination (Agri-View)
Spring 2020 results
- Press release (September 16, 2020): SWIGG study update – well sampling completed, analysis still ongoing (PDF)
- Radio report (September 16, 2020): Well sampling completed in southwestern Wisconsin study, but questions remain about contamination: Researchers seek to identify risk factors for well contamination (Wisconsin Public Radio)
Contact information
- Ken Bradbury (WGNHS), ken.bradbury@wisc.edu
- Joel Stokdyk (USGS), jstokdyk@usgs.gov
- Mark Borchardt (USDA), mark.borchardt@usda.gov
- Maureen Muldoon (WGNHS), muldoon@wisc.edu
- Katie Abbott (Iowa County), katherine.abbott@iowacounty.org
- Lynda Schweikert (Grant County), lynda.schweikert@wi.nacdnet.net
- Terry Loeffelholz (Lafayette County), terry.loeffelholz@lafayettecountywi.org
