What We've Learned

winter salt watch logo

The third season of Winter Salt Watch was our biggest yet! With over 750 reports submitted during the winter of 2019-20, we saw participation triple since the previous year. Concerned citizens across the country have learned about the connection between road salt and water quality and have shared their findings with us.

Lower Chloride Levels, but Not Better News

This winter's average chloride reading was 50 parts per million lower than last year's average, but this doesn't necessarily mean that road salting practices are improving. The decline could simply have been due to this season's mild weather, which kept both snowflakes and salt trucks off the roads in many places. In addition, it's likely that Salt Watchers in past seasons focused on waterways where they suspected salt pollution was a problem. As the project expands and more locations are tested, streams that have been relatively salt-free all along are now helping to bring down the average.

Participation Around the Country

This winter, we saw significantly more salt testing in Minnesota and Michigan, where volunteers consistently found high chloride levels. Testing also increased in Wisconsin, where many volunteers recorded chloride levels within the normal range. Strong participation from previous years continued in the DC and Philadelphia regions, where most streams had little salt, in part due to the very low snow totals in those areas this season.

Volunteer Data, Important Results

One important new finding from this season: Salt levels around DC and Philadelphia spiked when snow was predicted, even when the snow didn't actually arrive. This discovery underscores the importance of smart salting practices that reduce the amount of chloride going into streams while also ensuring safety on the roads.


Check out our maps to learn more.

This Year's Results

Click on a dot to see more data.


Salt Levels and Snow Totals

Click the clock icon to begin the replay of this season. Blue regions indicate snowfall. Green, yellow, and red dots indicate normal, abnormal, and toxic levels of chloride, respectively.


Increase in Salt Watch Testing

Blue dots indicate Salt Watch tests from the winter of 2018-19. Red dots indicate Salt Watch tests from the winter of 2019-20.

Did you know that road salt can be even more of a problem for streams in the summer? Help us learn more about how aquatic life is affected by high chloride levels and warm weather. Get your Salt Watch test kit now.


Results from Previous Years