By Jennifer Delgado, RAY Conservation Fellow Watershed Field Scientist
I think many of us are familiar with the light crunch of road salt under our feet and tires during those first thirty-degree winter days. It is the result of our collective preparation for the snow days ahead, and a preventative measure that urban spaces have implemented to protect pedestrians and drivers as they go through their daily schedule.
I am not going to lie, this whole concept of snow, ice, and salt is relatively new to me. Having grown up on the sunny side of the US, I think I had only experienced snowfall once during the Houston winter of 2008.
It was not until my first year at Carleton College in Minnesota, that I was introduced to a snow day, and road salt. Here I learned that road salt is applied to pavement before a large amount of snow falls. The chemistry is simple: road salt lowers the freezing point of water, making it more difficult for water to freeze and create dangerous driving conditions we want to avoid. It is a useful tool, no doubt, but it is one that comes with its own set of consequences as MyRWA and many other water management organizations around the northeast region have come to find.
What happens to a plastic bottle that is left out on the street? It will eventually either be blown or washed into our storm drains, go through our stormwater system, and then eventually into the river. This same thing happens with the salt that we apply onto our roads during the winter. It gets washed into storm drains and eventually ends up directly in the river system.
Unfortunately, salt is exceptionally good at creating chaos in a natural system, especially water systems since it can stay in the watershed for a long time during dry spells. The salt that you apply to your sidewalks and roads can reach beyond surface water systems, soaking into the soils and eventually the groundwater system.
The potentially harmful component of the salts that gets applied to roads (for example sodium chloride) is chloride, a pollutant that degrades the ecological quality of freshwater systems. Freshwater ecosystems like the Upper Mystic watershed possess a low threshold for heightened levels of chloride. Meaning that an increase in chloride concentrations in water for long periods of time within these ecosystems can create stress and toxic environments for freshwater organisms, from fish to dragonfly larvae to native plants.
Figure 1. Specific conductance of water (a parameter that increases with chloride concentration) in Mystic River over 20 years. Note apparent increase in all seasons, not just winter.
During the last 20 years, MyRWA has been gathering data at 10 sites around the watershed in our baseline monitoring program. We have been measuring conductivity (a variable used to measure the chloride levels in water) over time at each site and have illustrated a clear trend (figure 1) of increasing chloride concentrations within the watershed. We have known that the chloride concentrations within the watershed community are on the rise and are affecting the ecology and health of Mystic River systems.
We also deployed a real-time sensor in a pilot study in the winter of 2022 that showed evidence of chloride concentrations in excess of the state water quality standards for chronic and acute toxicity to freshwater organisms in Alewife Brook (figure 2).
Figure 2. Estimated chloride concentrations in Alewife Brook related to air temperature and precipitation data during winter 2022.
Now thanks to a grant from the Massachusetts Department of Environmental Protection (MA-DEP), MyRWA and six other watershed organizations (figure 3) have created the Eastern Massachusetts Water Quality Monitoring Coalition that will focus on collecting and submitting conductivity data to MA-DEP as well as analyzing the drivers of high chloride levels in our water systems. MyRWA will deploy conductivity loggers in eight individual bodies of water within our watershed twice for three month-long periods while collecting and analyzing the water data every month.
Figure 3. Coalition Watershed Extent Map, Eastern, MA.
I will admit the first time I joined Andy in the field to deploy our very first conductivity logger in Alewife Brook, I had a vague sense of what we would be doing. Reading the deployment procedures in the lab and then actually following the procedures in the field are quite different (figure 4). On paper, they do not tell you how much bushwhacking you have to do to get to the site, or how much arm strength you need to lift a cinder block attached to a rope out of the water. They also don’t warn you about the technical difficulties you may encounter with your loggers and other equipment.
Figure 4 Field work pictures featuring the software used to gather the data (left) Andy and Jennifer viewing data (middle) and the initial recovery of the logger (right)
All of this is to say that the first deployment has been successful, and that we are on our way to finishing the first installation of our loggers. We are looking forward to gathering the data, analyzing it, and advocating for specific policy change at the state level, recommending best practices such as those being piloted in the City of Cambridge. Stay tuned for the results of this research by following our updates on the MyRWA news page!
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This Chloride Testing is part of MyRWA's water quality program — that also includes our monthly baseline monitoring program. Through this effort every month volunteers collect water quality data at 15 sites in the watershed. These data are then used by the Mystic River Watershed Association and the United States Environmental Protection Agency (EPA) to publish the annual report card outlining what grade the rivers, lakes and tributaries earned during the year. The data has made headlines and on-the-ground improvements. This year for #Giving Tuesday, MyRWA is asking for donations to fully fund five out of the 15 water quality testing sites for a whole year. Join MyRWA for #GivingTuesday, a global generosity movement unleashing the power of people and organizations to transform their communities and the world, with a gift today. Celebrated on the Tuesday following Thanksgiving (in the U.S.), #GivingTuesday kicks off the charitable season.
