Pesticide Monitoring in Unusual Winters

Paige Weigand here with the Montana Pesticide Stewardship Partnership Program (MT PSPP).

While the snow was on and off this month, the PSPP team was ON! This month, we:

·        Conducted winter sampling on 8 of our “focal” sites from 2025 

·        Continued to evaluate new sites for our 2026 Monitoring Plan, which will allow for a projected 700+ samples this year

·        Began preparing for the field season, which begins in April, by doing an inventory of our sampling supplies and equipment

How is winter sampling affected by this unusual winter?

This winter in Montana, we are experiencing unusually low snowfall. 46% of SNOTEL stations (short for SNOwpack TELemetry) in Montana are in a snow drought. (Snow Drought Current Conditions)

From a PSPP perspective, winter sampling is extremely valuable because it can help us to distinguish groundwater-driven pesticide inputs from those in our surface water runoff. During an average Montana winter, when rainfall and irrigation are minimal, and snowpack dominates the landscape, pesticide detections are more likely associated with groundwater feeding streams (aka “baseflow”). During the spring, summer, and fall months, when we collect the bulk of our samples, pesticide detections can be dominated by surface water runoff (but also contain groundwater inputs).

So, when rain is falling during months usually characterized by heavy snowfall (like right now!), this can make the situation more complicated, with surface water inputs occurring when they are unexpected. We are working hard to avoid surface water runoff inputs during winter sampling by sampling on cold (below freezing) and dry days.

As always, if you or your watershed group would like to get involved with PSPP sampling this year, don’t hesitate to contact me at paige.weigand@flbs.umt.edu.

Looking forward to another productive month ahead as we inch closer and closer to the field season!