Imagine, for a moment, that you are a fathead minnow. Like many of your species in the Midwest, you are probably moving a little slower as the water temperatures fall. But the cold is no bother compared to another change coming this winter – toxic doses of chloride delivered primarily through salt from winter maintenance of roads, parking lots, and sidewalks.
A 2010 US Geological Survey study showed that at 168 monitoring locations in northern metropolitan areas, 55% exceeded chronic (230 mg/L) toxicity levels and 25% exceeded acute (860 mg/L) toxicity levels from November through April, with a much lower percentage exceeding either level during the warmer months. Additional local monitoring in 13 Milwaukee streams revealed that seven of those streams were likely to reduce your weight (not a good thing for fathead minnows) and survival.
In addition to negative effects on fathead minnow health and the health of other aquatic critters, most communities spend far more on road salt than needed to keep people safe. A 2014 Minnesota Pollution Control Agency study showed that a modest 10% reduction in salt use in the Twin Cities Metro area could maintain the same levels of safety and service while saving over $8 million.
Finally, unlike nitrogen – another common water pollutant when in excess – road salt is “sticky.” Most of it stays in the watershed where it is applied, accumulating to dangerous levels over time.
We have a few fathead minnows in my own home watershed, Lake Wingra. This chart from the draft 2015 Lake Wingra Watershed Plan shows what’s been happening to Lake Wingra’s chloride concentrations over time. Not a promising trend!
Fortunately, we know from our friends in Minnesota that a lot can be accomplished through education and training. Extension has provided some support for this training in some states (e.g. Michigan). What are you doing in your home state? Is there more that Extension could do to help municipalities save money, keep people safe, and improve the health of our lakes and streams at the same time?
SAVE THE DATE! The North Central Region Water Network’s second conference and
regional working session will be March 21-23, 2016 in Lincoln, NE. Theme: “From Science to Success.” More details coming soon!
Rebecca Power, Network Director