Road salt hurts rivers, lakes: Dartmouth study

Flora Krivak-Tetley, co-author of Dartmouth College study on harm caused by salt on lakes, rivers and ponds.

Joseph Blumberg, Dartmouth College

Salt can be good, and it can also be bad. Sprinkled on food, it makes things tastier, but it may also raise your blood pressure. Spread on winter roads, it can make driving safer, but the melting runoff contaminates nearby lakes and ponds.

In a study that gathered data from hundreds of lakes in the Northeast and the Midwest, a Dartmouth researcher and colleagues have found dramatic evidence of highway salt’s impact.

PhD student Flora Krivak-Tetley is co-author of a paper published in 2017 in the Proceedings of the National Academy of the Sciences that documents the impact of road salt—predominantly sodium chloride—on Northeastern and Midwestern lakes. Of the 371 lakes analyzed, “44 percent were found to have undergone long-term salinization,” the authors write.

Krivak-Tetley says the increasing concentration of salt in lakes and ponds is generally acknowledged as a growing problem. However, she says, “this is the first paper to say so and back it up with long-term data.”

Mirror Lake in New Hampshire’s Hubbard Brook watershed was an early highway casualty. In the mid-1970s, when Interstate 93 was constructed nearby, salty runoff began to flow into the lake. By ’97, scientists determined that the lake’s chloride concentration had tripled.

“This was a perfect example of how drastic it can be when there is a sudden change,” says Krivak-Tetley “It was this really undeveloped area, and then I-93 came in.”

The report also emphasized the critical role pavement is playing. In places with a snowy winter and heavy use of road salt, there is a direct connection between the amount of development around the lake and the lake’s increasing salt concentration over time.

Rather than being absorbed into the ground, the salty runoff drains across the paved surfaces and into neighboring water bodies. Lakes with surrounding land cover that was more than 1 percent paved were found to show increasing levels of chloride content.

The study evaluated lakes of at least 10 acres within the North American Lakes Region (NALR), an area comprising Connecticut, Maine, Massachusetts, Michigan, Minnesota, New Hampshire, New York, Ontario, Rhode Island, Vermont, and Wisconsin. The team gathered, scrutinized, and presented long-term data collected over a 10-year period by groups such as the U.S. Geological Survey and the U.S. Environmental Protection Agency.

The scientists estimated that 7,700 in this region could be facing elevated chloride. However, they suggest that this “is likely an underestimate, as it does not consider regions of heavy road salt application where no long-term lake data were available, such as Québec or the Maritime provinces of Canada.”

“There are a lot of places where salt use could be reduced if people are aware it’s a good thing to do,” says Krivak-Tetley. “They already do that in the Mascoma watershed locally where there are ‘no-salt’ zones.”

She says that once the salting is stopped, it will begin to flush through the system. “Most lakes have water flow in and water flow out so, if you just stop using salt, it will wash out over the course of some years with a decrease in the concentration in the lake water.”

“Clearly, keeping lakes fresh is critically important for protecting the ecosystem services freshwater lakes provide, such as drinking water, fisheries, tourism, recreation, irrigation, and aquatic habitat,” the paper concludes.

Categories: Environment

Tagged as:

7 replies »

  1. A study was needed? How about just common sense? OF COURSE salt has an impact. How much moiney did some Dartmouth U folks get for this no-brainer?

  2. A few years ago the people of the NEK noticed a lot of New Hampshire cars using the highway on the Vermont side of the Connecticut River between Lancaster and Colebrook (Route 102). This consequently had an effect on our roads. Why did it happen? A salt reduction in New Hampshire. What’s the alternative ? I’m not a chemist, I don’t know but it should not be icy, unsafe roads.

  3. The answer is simple, if you can’t drive on snow covered roads, move somewhere warmer. Today’s cars are head and shoulders better performing in snowy conditions than the cars I grew up with the 60s and 70s, and yet VT continues its defacto bare roads policy. Plow the roads, buy good tires, use good judgement and judiciously use sand with enough salt to keep it from clumping when icy conditions are present. Sand and sediment runs into water bodies every time it rains…no big deal.

    • It’s not the snow that’s a big deal – it’s the ice that forms immediately on untreated roads/walkways when they are untreated or under-treated. Icy conditions are extremely dangerous no matter how much one slows down, uses caution, etc. As long as the temps are freezing or below, ice forms & continues to form on surfaces, hence they must be continually treated. That being stated, there are a number of de-icing treatment alternatives to salt that are effective and precisely why Vermont refuses to use them or even use them to some degree along with salt, I have no idea – other states do.

      Perhaps VT politicians have stock in the auto industry…..as in addition to the effects of salt on water bodies, the effects of it on our undercarriages is catastrophic…….no matter how many times you wash your vehicle.

  4. Does anybody else notice that people with a hyphen between their two last names always find things that harm the environment? Maybe we should stop funding all of these non-profit organizations so that these people have to go find a real job!

Leave a Reply