The primary goal of the MDA's pesticide groundwater monitoring is to provide detailed information on the occurrence and concentrations of pesticides in Minnesota's groundwater resources. Protection of Minnesota's citizens and water resources from agricultural chemicals is the fundamental purpose of this goal. The program focus is monitoring vulnerable groundwater in the agricultural and urban areas of the state.

In 2019, the MDA’s ambient monitoring program sampled over 160 monitoring wells, naturally occurring springs and private drinking water wells throughout the state for pesticides.

Map illustrating the location of the groundwater sampling sites in 2019. Sampling sites include domestic wells, monitoring wells, urban wells, and springs.


In 1987, the Minnesota Legislature amended the Minnesota Pesticide Control Law. It directed the MDA to determine the impact of pesticides on the environment, including the impacts on surface water and groundwater.

In response to this charge, the MDA initiated a pesticide groundwater monitoring program in 1987 and in 1991, began surface water monitoring. The MDA has one of the most comprehensive pesticide monitoring programs in the country.

Groundwater Monitoring Results for 2019

  • 611 pesticide samples were collected from 166 routine groundwater monitoring sites (monitoring wells, springs and private drinking water wells).
    • 47 different pesticides or pesticide degradates were detected out of 150 pesticide analytes that were analyzed by the MDA Laboratory.
    • Metolachlor ESA was the most frequently detected analyte.
    • Glyphosate, and its degradate AMPA, were not detected in groundwater (167 samples).
    • Glyphosate/AMPA samples were collected at least once from every groundwater site.
    • 11 pesticides were analyzed for the first time in 2019.
    • Cyanazine acid, cyanazine amide, and deethylcyanazine acid were detected in 2%, 2%, and 4% of samples collected statewide, respectively.
    • Acifluorflen, afidopyropen, deethylcyanazine, deethylcyanazine amide, flutianil, flutianil OC 56574, flutianil OC 56635, and pydiflumetofen were not detected.
    • The total concentration of cyanazine and its degradates exceeded the drinking water Health Risk Limit (HRL) of 1,000 ng/L in one sample collected from a spring in Goodhue County. This was the only exceedance of a drinking water reference value in the ambient groundwater monitoring.

Common Detection Pesticides

Common detection is an official state designation made by the MDA Commissioner of Agriculture and is defined as “detection of a pollutant that is not due to misuse or unusual or unique circumstances but is likely to be the result of normal use of a product or a practice” (Minn. Stat. § 103H.005, Subd. 5). Pesticides, and select degradates, that have been designated as “common detection” receive heightened scrutiny from the MDA during reporting of monitoring results. Acetochlor, alachlor, atrazine, metolachlor, and metribuzin are the current common detection pesticides. Atrazine, metolachlor and metribuzin were designated in 2002. Acetochlor and alachlor were designated in 2003.

The graphics below indicate statewide groundwater common detection pesticide detection frequency from 2009 through 2019. Also presented are the annual statewide 90th percentile concentrations for common detection pesticide primary degradates.

Pesticide detection frequency for statewide groundwater monitoring 2010-2019. The following pesticides are graphed and values include the pesticide plus their degradates: Acetochlor, Alachlor, Atrazine, Metolachlor, and Metribuzin. Detection frequencies range from about 67% to less than 10%. Over time, the line for Metolchlor is relatively flat, values are between 60-70%. Alachlor and Atrazine both have a decreasing slope, values fall within 40-15%. Metribuzin has slight decline all values under 10%. Acetochlor show a slight increase over time, values fall between 25-40%.
Statewide groundwater monitoring 2010 - 2019 time series. 90th percentile concentration (ng/L) is plotted by year. Metolachlor ESA concentrations are the highest, and have the largest increase from 2013 to 2019. Acetochlor ESA has slight increase from 2010-2017, and slight decrease from 2017-2019. Alachlor ESA has a steady decrease from 2009-2019. Metribuzin DADK and Desethylatrazine appear to be relatively flat, all values below 0.25.

Data Availability and Future Work

All of the pesticide data collected as part of MDAs ambient monitoring program is publicly available through the Water Quality Portal or by contacting the MDA. The MDA will continue to improve its program to expand monitoring to new locations and to include additional pesticide analytes, as resources and needs permit. The MDA is committed to maintaining its long-term data record to allow for continued assessment of the impacts of pesticides on groundwater from routine use.