Drinking water high in nitrate can cause serious health effects in infants. The state’s Health Risk Limit (HRL) for nitrate-nitrogen is 10 mg/L. Karst geology makes the region’s groundwater especially vulnerable to nitrate contamination.  Because of this risk it is important to monitor for high nitrate concentrations in private wells.

In 2006, nine southeast Minnesota counties coordinated planning to develop a Volunteer Nitrate Monitoring Network (VNMN) to monitor long term trends of nitrate concentrations in private drinking water wells throughout southeastern Minnesota. From 2006 until 2012 the Project team included nine southeastern Minnesota counties and multiple state agencies funded by the EPA 319 Program and the MPCA Clean Water Partnership (CWP) Program. The first two years of the project were primarily the planning stage, the first round of samples were collected in 2008.  In 2013, the program was changed to incorporate more analytes in selected wells, but was no longer sampling the entire network for nitrate.  In 2014, the MDA coordinated with the County Water Planners and Southeast Minnesota Water Resources Board (SEMNWRB) to continue sampling all of the wells in the network on an annual basis to determine long term trends and keep the original network intact where possible.

Homeowners are the cornerstone of this network, this work could not be done without them. Network participants are sent a nitrate test kit directly to their home on an annual basis by the lab. The homeowner simply fills up the bottle and sends it directly back to the lab for analysis. The lab then sends homeowners their results. 

In 2022, 376 private drinking water wells were sampled for nitrate. Results from 2022 are similar to previous years:

  • 69.4% of nitrate results were < 3 mg/L
  • 22.3% of nitrate results were 3<10 mg/L
  • 8.2%  of nitrate results were ≥10 mg/L

Southeast Volunteer Nitrate Monitoring Network Summaries

The nitrate testing results from this network of private wells is used in combination with other networks to determine the trend of nitrate levels in regional groundwater over time. The nitrate results and trend reports are available in the Minnesota Water Research Digital Library. Links to the most recent reports are listed below.

Yearly Results

Older reports are available in the Minnesota Water Research Digital Library. Search for reports using the following titles: Southeast Minnesota Volunteer Nitrate Monitoring Network, or Southeast Minnesota Domestic Well Network.

Trend Reports

An overview:

  • Nine counties in the Southeast region participate in the county wide private well network
  • In 2020, 381 private drinking water wells were sampled for nitrate , 91% have water that is below the HRL 
  • Nitrate analysis of approximately 300-600 wells have been completed annually
  • This project will help answer the question: Are nitrate concentrations in private drinking water wells increasing, decreasing or staying the same?

Why is this program focused on nitrates?

Nitrate is a water soluble molecule that is made up of nitrogen and oxygen. It is naturally occurring in the environment; however at elevated levels it can have negative effects on human health. According to a 2007 Minnesota Pollution Control report, nitrate is one of most common contaminants in Minnesota's groundwater, and in some areas of the state a significant number of wells have high nitrate levels (Minnesota's Ground Water Condition: A Statewide View, MPCA 2007). The U.S. Environmental Protection Agency (EPA) has established a drinking water Maximum Contaminant Level (MCL) of 10 mg/L for nitrate-nitrogen (EPA, 2009). Although nitrate occurs naturally, it can also originate from man-made sources such as fertilizer, animal manure and human waste.

Regions of Minnesota most vulnerable to nitrate contamination are central and southeastern Minnesota. Central Minnesota counties are vulnerable because of widespread sandy soil and regions of southeast Minnesota are vulnerable because of shallow bedrock, sinkholes and underground caves (referred to as karst geology), which lead to exchanges between surface and ground water resources.

County Partners:

Dodge, Fillmore, Goodhue, Houston, Mower, Olmsted, Rice, Wabasha, and Winona. The Olmstead Soil and Water Conservation District is the local partner contact.