Study finds receding nitrate poison in groundwater

ST. PAUL, Minn. – New scholarship has found the nitrate contamination in Winona County groundwater is receding. So too is ground water throughout the massive Driftless Region’s thick underground strata of porous limestone. How is this happening? Improved farming practices, said the University of Minnesota-based research team. Their work appears in a 25-page report the current issue of yhe scholarly and peer-reviewed Hydrology Journal. While the researchers found compelling evidence of less nitrate entering groundwater, it’s a persistent contaminant that’s still down there but moving deeper and below the range of and an increasing number of wells and springs. The researchers examined concentrations of a discontinued row-crop herbicide, popular in the 1970s and 1980s, in springs and wells. That data was then was checked against the historical use of the herbicide. They then cross-checked their data with:
> Groundwater from 10 to 40 years ago in shallower springs and wells.

> Water in deeper aquifers thousands of years old.

The more recent data were from nearly 1,200 wells, springs and streams between 2000 and 2021. The study found that most monitoring sites over the last 20 or so years with either decreasing or relatively steady nitrate levels. Besides improved agricultural practices, the researchers believed that record-setting precipitation has helped dilute nitrates at upper levels.

Driftless Region. The two major plateaus in the region’s southeast Minnesota counties.