Chloride Trends in the Rum River Watershed

The Metropolitan Council (MCES) put out a report on the trends of chloride in the Rum River Watershed. This report was based on data collected from 2001 to 2019 by both the MCES and Anoka Conservation District. Chloride concentrations have been rapidly rising in many waterbodies, including shallow aquifers, throughout Minnesota. This is a worrying trend because chloride is a permanent water pollutant that is toxic to fish, aquatic bugs, and amphibians. The main sources of chloride pollution in Minnesota comes from livestock excreta, household water softening, synthetic fertilizer, and de-icing salt. Chloride concentrations can be greatly affected by other factors like season, precipitation, and streamflow. During the winter months, concentrations rise with the use of approximately 400,000 tons of de-icing salt on Twin Cities' roads. Precipitation and streamflow also affect the concentration by dilution during high flow and precipitation years and concentration during low flow and precipitation years.

Luckily, the MCES found that concentrations of chloride are generally low in the Rum River. Chloride was increasing from 2001 to 2012 but has remained stable since 2012. Although this is a good sign, climate change is creating a wetter, warmer climate in Minnesota. This will greatly affect the freeze-thaw cycle and will have an unpredictable affect on pollution dynamics. Understanding how pollutants like chloride can affect Minnesota's waterways is an important step in keeping our waterways clean.
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