The nitrate testing results from a network of private wells is used to determine the trend of nitrate levels in regional groundwater over time.


Residents in certain areas of the state are invited to participate in the MDA's private well network. Participation is voluntary and easy. Participants collect and mail water samples from their drinking wells using the provided test kits and prepaid postage.

Our agency collects the data to determine the trend of nitrate levels in regional groundwater over time. To the greatest extent possible, the same households are tested each year. This allows us to track nitrate levels to see if they are increasing, decreasing or staying the same.

Currently, our agency is working with two networks in the state. The groundwater in each area is vulnerable to nitrate contamination. Nitrate can move easily through the soils and geology of these regions. Sandy soils exist in the central region of Minnesota and sinkholes and underground caves can be found in southeast Minnesota (karst geology).

  1. Central Sands Region
  2. Southeast Karst Region

How does it work?

Each network is a cooperative partnership with the counties of the region. Great efforts are made to ensure that participating households are randomly selected and evenly distributed across the region. Once selected, homeowners are invited to participate and asked to share information about their well's construction, depth, age and other descriptive features. Participating homeowners send their water samples and well survey information back to the lab listed on the prepaid return envelope.

Why does this program focus on nitrate?

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 (USEPA) has established a drinking water Maximum Contaminant Level (MCL) of 10 milligrams per liter (mg/L) for nitrate-nitrogen (U.S. EPA, 2009).

Although nitrate occurs naturally, it can also originate from man-made sources such as fertilizer, animal manure and human waste.

Who is most “at risk”?

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.  

Well Network Partners

Central Sands County Partners: Becker, Benton, Cass, Crow, Douglas, Hubbard, Kandiyohi, Morrison, Otter Tail, Pope, Sherburne, Stearns, Todd, and Wadena.
**Wadena County Soil and Water Conservation District is the lead local project coordinator and RMB Environmental Laboratories analyzes the samples.

The Southeast County Partners: Dodge, Fillmore, Goodhue, Houston, Mower, Olmsted, Rice, Wabasha, and Winona. The Southeast Minnesota Water Resources Board is the lead local project coordinator and Southeastern Minnesota Water Analysis Laboratory (SEMWAL) analyzes the samples.