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Groundwater study: More private wells should be tested

Posted at 13:15 on August 31, 2017

The Brillion News

MADISON – Because Wisconsin’s groundwater resources play a critical role in human health and the economy, it’s important that more private well owners test their wells on a regular basis. That’s one of the findings in the 2017 annual Wisconsin Groundwater Coordinating Council Report.

The report said that nearly three-quarters of Wisconsin residents rely on groundwater as the primary source for their drinking water.

“Unlike public water systems, protection and maintenance of private wells is largely the responsibility of homeowners,” said Pat Stevens, Environmental Management Division administrator for the Department of Natural Resources and council chairman. “We recommend that private well owners test their water at least once a year for coliform and E. coli bacteria, important indicators of health risk.”

In some counties, such as Dane, Portage and Kewaunee, more than 10 percent of private wells, on average, are tested for coliform bacteria each year. However, the state average of private wells tested annually for total coliform bacteria is only about six percent.

The Groundwater Council’s report also shows some positive movement in nitrate contamination across the state.

“Nitrate is Wisconsin’s most widespread groundwater contaminant, and it correlates with the presence of other contaminants,” said Bruce Rheineck, DNR Groundwater Section chief. “The report includes a finding that 11 counties – including Polk, La Crosse and Wood – show decreasing nitrate concentrations. The decrease in these counties represents a positive trend.”

Rheineck added that ongoing monitoring will be needed to help show how pervasive the trend is and whether beneficial agriculture practices in these counties may be applied in other areas. A home well also should be tested for nitrate at least once a year, and on a regular basis if there is agricultural activity in the area.

The 2017 report notes the steps taken to protect groundwater from contamination and helps the public better understand the sources and distribution of naturally occurring contaminants in groundwater. It also highlights the need for ongoing research into the factors that affect groundwater supplies and helps identify next steps to protect and preserve our valuable groundwater resources.

The major recommendations from the report include:

  1. Evaluate the occurrence of viruses and other pathogens in groundwater and groundwater-sourced water supplies, and develop appropriate response tools. Viruses and other microbial pathogens have been found in municipal and domestic wells, challenging previous assumptions about their persistence and transport. Monitoring and assessment should focus on refining our understanding of pathogens in groundwater, in particular where and when they pose threats to human health. Agencies should also work with partners to increase awareness of waste disposal choices, their risks and costs.

  2. Implement practices that protect groundwater from nitrate and other agricultural contaminants (microbial agents, pesticides and their degradates). Nitrate that approaches and exceeds unsafe levels in drinking water is one of the top drinking water contaminants in Wisconsin, posing an acute risk to infants and women who are pregnant, a possible risk to the developing fetus during very early stages of pregnancy, and a chronic risk of serious disease in adults. In addition, pesticides are estimated to be present in approximately 40% of private drinking water wells in Wisconsin. Areas of the state with a higher intensity of agriculture generally have higher frequencies of detections of pesticides and nitrate. Agencies should develop and evaluate a strategy to promote practices that lead to efficient use of nitrogen and careful or reduced use of pesticides in order to protect drinking water sources. Implementation of these practices should be supported with appropriate technical tools and incentives.

  3. Support the sustainable management of groundwater quantity and quality in the state to ensure that water is available to be used, which will protect and improve our health, economy, and environment now and into the future.

The Groundwater Coordinating Council was formed in 1984 to help state agencies coordinate activities and exchange information on groundwater.

To see the executive summary of the report, visit



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