Increasing Salinity in Vermont’s Lakes: Prevention is Key to Protection

A new study on increasing salinity levels in freshwater lakes around North America has been in the news recently. The study used data from 371 lakes, including Lake Champlain and several others in Vermont. Researchers found that chloride, the major contributor to salinity in freshwater, has been increasing in many lakes around North America during the last several decades. If the trend continues over the long-term, chloride levels could become high enough to harm some lake organisms. Most of this chloride is reaching surface waters through winter road deicing. The study notes that impervious land cover (parking lots, roofs, roads, and other hard surfaces) is a strong predictor of chloride trends here in the Northeast.

Lake Champlain was highlighted as one of the lakes showing a trend of increasing chloride. The Lake Champlain Long-Term Water Quality and Biological Monitoring Project has been tracking chloride since 1990 and has documented increased chloride in all areas of the lake. Because of these findings and other data from around the Northeast, the Watershed Management Division added chloride criteria to the Vermont Water Quality Standards in 2014, representing the maximum level allowable without harm to aquatic life. The Division, working together with partners and stakeholders, identifies watersheds around the state with elevated chloride levels so that outreach and chloride reduction efforts can get underway. While the increasing trend in chloride in Lake Champlain is noteworthy, levels are very low relative to the limits in the Vermont Water Quality Standards.

Winter deicing practices around Vermont and the Northeast utilize road salt (sodium chloride) and some calcium chloride to keep roads safe. The Vermont Agency of Transportation and many local municipalities have implemented smart deicing practices that include applying the amount of sodium chloride needed to keep roads open for travel while reducing the impact on water. Homeowners, business owners, and private maintenance companies can also protect Vermont’s waters by carefully applying deicing salts and other products throughout the winter.

To learn more about the harmful impacts of salt on aquatic organisms, read the Division’s summary of chloride impacts. Homeowners and business owners can watch this video to learn about the best tools to remove snow and ice.


The charts above show chloride concentrations (mg/L) over time at selected Lake Champlain stations. (Data source: Lake Champlain Long-Term Water Quality and Biological Monitoring Project)