Study of water in 3 southwestern Wisconsin counties points to solutions for protecting private wells

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MADISON – Private wells in southwestern Wisconsin are more likely to have higher levels of fertilizer, animal manure and human waste than other parts of the state, according to a new study.

Clean water advocates say the study is a breakthrough in that it points to solutions to protecting water coming from private wells in a state where about a quarter of residents rely on wells not tied to municipal water systems. Wisconsin has more than 800,000 private wells, according to state figures.

The Southwest Wisconsin Groundwater and Geology, or SWIGG, analyzed nearly 1,000 samples drawn from more than 800 private wells in Grant, Iowa and Lafayette Counties in 2018 and 2019. Researchers also studied the geology of the area and how the age and types of wells and the proximity of septic systems and farms impacted the well water serving families throughout the region.

The study, published Tuesday, is one of only two studies in Wisconsin to look at a multitude of factors that may be contributing to contamination, said Joel Stokdyk, an author of the study and a biologist with the U.S. Geological Survey.

Of the 840 samples analyzed particularly for nitrate, total coliform bacteria and E. coli, 271 wells were positive for total coliform bacteria and/or had nitrate greater than the Wisconsin and U.S. Environmental Protection Agency health standards, which are 10 parts per trillion.

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Those numbers, the report says, were generally greater than statewide averages for private wells.

Another 138 tests were also used to distinguish between contaminants from human wastewater, cattle manure or pig manure. Human wastewater was detected in 64 of those wells, cattle manure was detected in 33 and pig manure was detected in 13, indicating that both human waste and animal waste is contributing to contamination issues.

Human waste can seep into groundwater from leaky or faulty septic tanks, whereas animal waste gets into water at farms or by the over-application of waste to farm fields as fertilizer.

In addition to the common tests and the tests distinguishing between types of waste, researchers also tested 138 wells for pathogens like viruses or bacteria. Pathogens were detected in 66 of those wells, but the sources for those were unknown.

Researchers also looked at the siting of the wells, the geology of the area, rainfall and groundwater levels during their research, because those factors tend to impact whether contaminants end up in drinking water. They found that nitrate was more often found where the geology allows for the rapid flow of water.

More: Email reveals DNR has abandoned groundwater rulemaking for nitrates, citing strict timeline and difficult process set by Legislature

Microbial contamination was found in greater numbers following rainfalls, or where the bedrock is closer to the surface layer of soil.

Both types of contamination were also found more often in older, shallower wells, though that does not mean that older wells were all impacted by nitrates and/or microbial contamination.

"I think one of the broad outcomes was the fact that so many factors are important in contributing to private well contamination," Stokdyk said. "If you just look at the results for one contaminant, that's only one part of the story. It's important to consider these elements not in isolation."

Lafayette County resident Kriss Marion, who has for years been championing action for water quality in the southwestern portion of the state, said the study came with both good and bad news.

The bad? That people are consuming a whole lot of poop.

But on the other hand, the study showed previously unknown solutions for contamination.

"It appears that the bedrock separates a fair amount of our groundwater into two aquifers, a shallower one and a deeper one. The deeper one is cleaner," she said. "If we were to construct wells that were deeper, we could access clean drinking water."

More: UW study finds elimination of air pollution could save more than 53,000 lives each year in the U.S.

Drilling deeper wells could be more expensive, but Marion said the state could develop a cost-sharing program to help.

Clean Wisconsin, which advocates for clean water, celebrated the findings and asked the state to begin implementing solutions for the issues the study highlighted.

"Southwest Wisconsin needs a thriving, resilient agriculture industry and clean drinking

water. Farmers and families deserve both, and if we work together, we can have both," water program director Scott Laeser said.

"It's clear we have to tackle several aspects of water resource management to deliver on Wisconsin's clean drinking water promise. How we construct our wells, build and maintain our septic systems, and raise our crops and livestock must change to protect our drinking water resources and the Wisconsin families who rely on them."

Marion said one approach to solving the issues highlighted in this study could be action taken by the legislature to regulate contaminants or to put stricter guidelines on how manure can be spread on fields as fertilizer.

But aside from legislation, local communities and individuals can do more to help prevent contamination in groundwater.

"For many, many years, people have taken for granted that when they turn on their tap, the water is going to be good," Marion said. "Everyone could do better."

Laura Schulte can be reached at and on Twitter at @SchulteLaura.

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This article originally appeared on Milwaukee Journal Sentinel: Private wells in southwestern Wisconsin are impacted by human waste