Protecting drinking water in Minnesota’s karst region from industrial agriculture pollution

Since the 1990s, animal feedlots and crop production in Minnesota have become bigger and more industrialized. At the same time, monoculture crop production of nitrate-intensive crops like corn and soybeans has grown. This industrial-scale mode of production has pushed out smaller, more sustainably run farms who can’t compete. It has also caused the widespread contamination of drinking water by nitrate, pesticides, and other agricultural pollutants. This contamination is particularly bad in geologically sensitive areas where erodible bedrock or sandy soils allow nutrients and chemicals to rapidly infiltrate into groundwater. Where water moves quickly from the surface into underground aquifers, drinking water is at risk.

Southeastern Minnesota is home to such vulnerable geology, known as “karst.” This region of Minnesota is vulnerable to groundwater contamination and has a lot of Concentrated Animal Feeding Operations (CAFOs) as well as monoculture crop production. It is also home to some of Minnesota’s best and most beloved trout streams. The impacts of water pollution from industrial agriculture in the karst region are widespread, persistent, and pose a major risk to human health and aquatic life. While the impacts to people can be harder to see, the consequences for aquatic life are startling. One of the most visible signs of this pollution are fish kill events, where thousands of fish die along a small stretch of a stream or river in a single day. A central cause of fish kills in the karst region is nutrient pollution pesticides, and fungicides from agricultural land use practices. In Winona County alone, three major fish kills – where thousands of fish died – happened between 2015 and 2022. 

CONDITIONS HAVE REACHED CRISIS-LEVEL IN SOME AREAS OF SOUTHEAST MINNESOTA

Nitrate contamination of drinking water in this region is well documented, and private wells and public water supplies routinely exceed the federal drinking water standard of 10mg/L, which is the human health limit established by the Environmental Protection Agency. In 2017, 19% of private wells tested in Winona County were at or above 10mg/L of nitrate. In some townships, such as Fremont Township, over half of the private wells tested in the same time period were above 10mg/L. The contamination has affected public water supplies too. Lewiston Township has already had to dig a deeper well because of nitrate contamination, and now Utica Township has to dig a deeper well also, for an estimated cost to taxpayers of over $2 million. It’s important to keep in mind that while the federal standard of 10mg/L was set in 1962 to prevent methemoglobinemia (also called “blue baby syndrome”), which is a serious health risk for infants and pregnant women, research has shown an increased risk for colorectal cancer and adverse birth outcomes from exposure to nitrate levels as low as 3-5mg/L.