Surface Water Pesticide Water Quality Monitoring

The Commissioner of the MDA has determined that the neonicotinoid insecticides clothianidin and imidacloprid are “surface water pesticides of concern” in accordance with the state Pesticide Management Plan (PMP). For more information on this designation and the supporting resources for the determination visit the surface water pesticides of concern page.

Monitoring

History

In 1987, the Minnesota Legislature amended the Minnesota Pesticide Control Law (MN Statute 18B.04). 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. In 1991, surface water monitoring began. The MDA also conducts edge-of-field water quality monitoring for nutrients and sediment. The MDA has one of the most comprehensive pesticide monitoring programs in the country.

Surface Water Monitoring Results for 2019

The MDA’s ambient surface water monitoring focuses on pesticide sample collection from rivers and streams around the state.

In 2019, 1,161 pesticide samples were collected from 55 river or stream monitoring locations for up to 166 pesticide analytes.

• 69 different pesticides or pesticide degradates were detected.
  • 39 were detected in 10% or less of the samples.
  • 12 were detected in 50% to 97% of the samples.
• The most commonly detected parent pesticide compounds were the herbicides 2,4-D, metolachlor, and atrazine detected in 85%, 79%, and 67% of samples, respectively.
• 3 neonicotinoid insecticides, clothianidin, imidacloprid, and thiamethoxam, were detected in 30%, 27%, and 11% of samples, respectively.
• 138 detections were above an applicable numeric water quality reference value, including acetochlor (11), atrazine (2), chlorpyrifos (3), clothianidin (62), dichlorvos (1), imidacloprid (58), and metolachlor (1).
  • Where state water quality standards are available, the Minnesota Pollution Control Agency (MPCA) will assess these detections, as well as the duration of concentration, for any applicable violations of standards.
  • Pesticides without state standards in the above list (clothianidin, dichlorvos and imidacloprid) are compared to U.S. Environmental Protection Agency (USEPA) aquatic life benchmarks.
• Glyphosate was detected in 10% of samples, and the maximum glyphosate detection (5,880 ng/L) was <1% of the lowest water quality reference value.
• Acifluorfen and deethylcyanazine acid were detected for the first time in Minnesota surface water in 3% and 15% of samples, respectively.
• 6 pesticide samples were collected from one lake and eight pesticide analytes were detected at concentrations well below the applicable water quality reference values.
• 43 pesticide samples were collected from four rainfall monitoring locations, and 20 pesticide compounds were detected.
• 3 pesticides are designated as "surface water pesticides of concern" by the Commissioner of Agriculture.

Surface Water Pesticide Impairments

 

Table 1. Minnesota pesticide impairments for currently registered pesticides.

Pesticide	Impaired Waters List Year	Stream	County	Violation that Resulted in Impairment
Acetochlor	2016	Silver Creek	Carver	chronic (3,600 ng/L) Minnesota water quality standard
Chlorpyrifos	2018	Beauford Ditch	Blue Earth	maximum (83 ng/L) Minnesota water quality standard
Chlorpyrifos	2018	Beaver Creek	Murray	maximum (83 ng/L) Minnesota water quality standard
Chlorpyrifos	2018	Chetomba Creek	Renville	maximum (83 ng/L) Minnesota water quality standard
Chlorpyrifos	2020	Double Lake	Cottonwood	chronic (41 ng/L) Minnesota water quality standard
Chlorpyrifos	2016	Dry Weather Creek	Chippewa	maximum (83 ng/L) Minnesota water quality standard
Chlorpyrifos	2020	Dutch Creek	Martin	maximum (83 ng/L) Minnesota water quality standard
Chlorpyrifos	2014/2016	Grand Marais Creek	Polk	maximum (83 ng/L) Minnesota water quality standard
Chlorpyrifos	2018	Jack Creek	Jackson	maximum (83 ng/L) Minnesota water quality standard
Chlorpyrifos	2018	Lac qui Parle River	Lac qui Parle	maximum (83 ng/L) Minnesota water quality standard
Chlorpyrifos	2018	Sleepy Eye Creek	Redwood	maximum (83 ng/L) Minnesota water quality standard
Chlorpyrifos	2014	Tamarac River	Marshall	maximum (83 ng/L) Minnesota water quality standard
Chlorpyrifos	2020	Three Mile Creek	Lyon	maximum (83 ng/L) Minnesota water quality standard
Chlorpyrifos	2020	Yellow Medicine River	Yellow Medicine	maximum (83 ng/L) Minnesota water quality standard

Three waterbodies have been removed from the USEPA 303(d) Impaired Waters List for currently registered pesticides. The Le Sueur River and Beauford Ditch were designated as impaired for acetochlor in 2008 and were removed from the USEPA 303(d) Impaired Waters List in 2014. Seven Mile Creek was designated as impaired on the 2012 Impaired Waters List for chlorpyrifos and was removed from the USEPA 303(d) Impaired Waters List in 2018. Removal from the USEPA 303(d) Impaired Waters List typically occurs after several years of water quality monitoring without pesticide detections above the applicable standards.

Visit the MPCA Minnesota Impaired Waters List for more information.

Chlorpyrifos Response Plan: This plan was developed in response to continued detections of chlorpyrifos in rivers, streams and lakes and the determination of chlorpyrifos water quality impairments of rivers and streams in agricultural areas of Minnesota.

Data Availability and Future Work

All of the pesticide data collected as part of the MDA's 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 surface water from routine use.