|BRADBURY, KEN - Wisconsin Geological And Natural History Survey|
|STOKDYK, JOEL - Us Geological Survey (USGS)|
Submitted to: Popular Publication
Publication Type: Popular Publication
Publication Acceptance Date: 9/30/2019
Publication Date: 9/30/2019
Citation: Bradbury, K., Borchardt, M.A., Stokdyk, J. 2019. SWIGG: The southwest Wisconsin groundwater and geology study. Popular Publication. p. 16-19.
Technical Abstract: The Southwest Wisconsin Groundwater and Geology (SWIGG) study is documenting the quality of drinking water produced by private wells in three southwestern Wisconsin counties and then examining relationships between water quality and local hydrogeologic factors. There are approximately 18,000 private wells supplying drinking water to 44% of the population in Grant, Iowa, and Lafayette Counties. Private wells in Wisconsin are not monitored or regulated by federal, state, or local government; instead, homeowners are responsible for the maintenance and testing of their well, including any treatment or corrective action to address contamination. The SWIGG study has three objectives: 1) Evaluate private well contamination in three counties using indicator bacteria (total coliform and E. coli) and nitrate based on randomized synoptic sampling events; 2) Identify fecal sources of contamination in a subset of total coliform- and nitrate-positive wells once per season using microbial tests that distinguish between human, bovine, and swine fecal sources. 3) Assess well construction and geological characteristics (e.g., well age, depth to bedrock) that affect total coliform and nitrate contamination. The first objective was completed through two synoptic (“snapshot”) sampling events (November 9-10, 2018 and April 12-13, 2019) that tested a total of 840 samples from randomly selected wells across the three-county region. Overall, 42% (November) and 27% (April) of sampled wells were positive for coliform bacteria or had nitrate-nitrogen concentrations greater than the drinking water health standard of 10 ppm. Next steps are to apply microbial source tracking (MST) methods to identify sources of fecal contamination in private well water and statistically relate well construction factors and land use practices to private well contamination. The study will be completed at the end of 2020.