Research shows Chesapeake Bay streams are getting saltier

With the arrival of spring, many freshwater streams in the Chesapeake Bay region will experience spikes in salt levels — coming mostly from the salt used to treat roads during winter, still working its way toward streams with spring rains.

And while efforts are underway across the region to reduce harmful salt in freshwater streams, research shows that salinity continues to rise.

John Jackson, a senior research scientist at the Stroud Water Research Center in Pennsylvania, said rock salt is now part of the water cycle. And even where it doesn’t flow directly into streams, it seeps into the earth and reaches groundwater and aquifers.

While plants and animals closer to Chesapeake Bay, especially in its more southerly reaches, have evolved to tolerate salty water, those in freshwater rivers and creeks have not. Any increase in salt can make it difficult for fish to regulate the salt in their body. For humans, salt can reach drinking water sources, contributing to heart and kidney diseases. The compound also corrodes infrastructure and increases toxicity of other contaminants.

To combat the problem, states and local jurisdictions in the Bay watershed are trying to reduce the use of road salt, and community groups are urging private property owners to do the same.

But it’s a challenge. Removing salt from your soup is already difficult. Removing salt from drinking water at a large scale is even more difficult — and much more expensive. Fairfax County Water Authority in Northern Virginia estimated it would cost over $1 billion to desalinate the drinking water it treats.

“Everything that you put down on the sidewalk that you don’t [remove] will end up in our waterways, and so everything will have some sort of impact,” said Renee Bourassa, communications director at the Interstate Commission on the Potomac River Basin.

The general advice is to simply use less. Adding more salt in a given spot doesn’t make snow melt faster. Bourassa said people only need a mug’s worth of salt for every three sidewalk squares.

Highway departments are working toward reducing their salt use while maintaining road safety. Maryland, Virginia and Pennsylvania now pre-treat roads with salt brine, which is a mix of salt and mostly water. The brine helps more of the subsequently added rock salt stick to the road.

Charlie Gischlar, spokesperson with the Maryland State Highway Administration, said using brine can reduce salt applications up to 30%. The department’s goal is to reduce salt use by 50%, he said, but especially snowy winters can work against that.

Virginia uses many of the same tactics and released its Salt Management Strategy Toolkit in 2020 as guidance for private groups and localities. Pennsylvania has a Strategic Environmental Management Program that provides guidance on reducing winter salt use. Virginia, Maryland and Pennsylvania used approximately 1.5 million tons of salt this winter.

Despite these efforts, salt levels are still rising in freshwater streams. A study by Rosemary Fanelli, hydrologist with the U.S. Geological Survey, found 68% of Chesapeake Bay freshwater streams had conductance levels — an indicator of salinity — 1.5 times above naturally occurring levels from 2014 to 2016.  

Levels of chloride from salt (sodium chloride) have increased in the Potomac and Patuxent rivers by 84% and 155% respectively over the last 30 years.

The Metropolitan Washington Council of Governments manages a project studying what it calls the “freshwater salinization syndrome,” which aims to analyze current salt trends and identify solutions for the District and its surrounding counties, cities and towns.

Sujay Kaushal, professor at the University of Maryland, is part of this project. The researchers found that even though the area has seen 40% less snowfall over the last 100 years, salt spikes are still occurring in its waterways.

One of the other lead scientists on the project, Virginia Tech professor Stanley Grant has studied salt levels in the Occoquan Reservoir as a microcosm of the region. Grant found that even though snowfall amounts had decreased in the surrounding area, peak salt levels were increasing. Grant found that development and extreme weather were the main drivers.

Fanelli’s USGS study also found that the greatest predictor of high conductance, besides geological features, was impervious surface.

Kaushal and his colleagues plan to meet with the Chesapeake Bay Program’s Scientific, Technical and Advisory Committee by the end of May to find solutions and risks.

“I think that this is a solvable problem,” Kaushal said. “I think that it will be reduced as we see what these possibilities are with the [monitoring results], and that it can be done. And then it just becomes political and social will at a certain point.”

State efforts may not be showing results because state roads are only a fraction of where salt is applied. Private properties like shopping centers and business campuses over-salt their lots to ensure they won’t be liable for injuries.

Jason Swope, lead instructor for Maryland’s Smart Salting Program, teaches property managers about best salt practices and encourages them to consider changes to their contracts to de-incentivize excessive salt use. For instance, instead of customers paying per bag of salt, they pay a fixed price.

Anthony Bishop, partner of Deicing Depot, is a wholesale distributor of salt. Bishop helps Swope train contractors. But he said the key to the shift is to get customer buy-in.

“Once [customers] saw the benefits, they understood that they were going to have less salt applied onto their properties, and it’s being applied where they needed, and not out in the grass or into their ponds,” Bishop said.

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