Private well testing highlighted in groundwater report

Wisconsin State Farmer

MADISON -Since 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 Groundwater Coordinating Council report. 

Water flows from a kitchen faucet

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 6 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. 

For more information, visit and search "Groundwater Coordinating Council."