Each year, over 20 million metric tons of road salts are applied to roads across the United States. The use of road salts and other de-icing agents is particularly prevalent in the Midwest and Northeast where winters are long, snowfall is abundant, and the pressure to maintain clear and safe roads is widespread.

Road de-icing agents often contain salts such as sodium chloride, magnesium chloride, potassium chloride, and calcium chloride that break apart when they dissolve in water. This human-induced input of dissolved salts into surface water and groundwater is a major driver of increased salinity in freshwater systems, especially urban streams like Kids Creek.

Chloride is known to have adverse and lethal effects on fish, invertebrates, and plants and may impact aquatic populations and food web dynamics. Further, high chloride concentrations in freshwater lakes can result in physical changes including annual lake mixing processes. To protect freshwater from salinization, chloride thresholds have been established by state and federal agencies. Even with these guidelines in place, it is predicted that many freshwater lakes with even low to moderate surrounding impervious surfaces will have chloride levels exceeding federal thresholds in the next 50 years if trends continue (article).