Road salt application differentially threatens water resources in Lake George, New York

Road salt (NaCl) application around Lake George, New York, resulted in nearly tripling in-lake salt concentration between 1980 and 2009. Salt concentrations measured in 8 streams between 2007 and 2009 ranging in development from pristine to moderate resulted in 4 significantly different groups based on chloride concentrations. Chloride concentrations were significantly correlated to the amount of roadway surface within each sub-watershed, with chloride concentrations in the most impacted stream approaching 200 mg/L. In the more impacted streams, chloride concentrations were significantly and inversely correlated to discharge rate. The high road density around the more developed south end accounted for similar to 30% of the estimated road salt application, which created a chloride gradient within the lake that decreased as water flowed north to the single outlet. The continual and disproportionate input of road salt near the southern end of the lake strengthened the gradient over time to create 4 significantly different regions within the lake. While the consistent lake-wide increase seems to be open-ended, a steady-state salt concentration within the lake may occur in the near future. Based on change of lake chloride mass and export from the lake (2007-2009), an average lake-wide steady-state chloride concentration of similar to 17 mg/L is expected, with some variation anticipated due to interannual variation in precipitation and the salt gradient within the lake.