By Marielena Lima, River Science Program Manager, Charles River Watershed Association
The Charles River Watershed Association (CRWA) is monitoring for chloride in the Muddy River due to concerns of salinization of freshwater streams from road deicer usage entering at stream road crossings. Freshwater systems are home to hundreds of species of fish, plants and macroinvertebrates that have evolved in low salinity environments. Therefore anthropogenic increases in salt can cause sublethal impacts on freshwater organisms such as negatively impacting growth rates as well as lethal effects (aka death).
Conductivity is a measure of the ability of water to pass an electrical current and is a known surrogate for chloride. CRWA deployed loggers that measure conductivity and temperature every 15 minutes upstream and downstream of Rt. 9 on the Muddy River in 2026.
Preliminary data shows that chloride concentrations are higher than the EPA chloride criteria thresholds for streams safe for aquatic organisms, but additional data collection through multiple seasons is needed for a more complete analysis.
CRWA will continue to assess baseline chloride levels in streams throughout the watershed. Collected discharge data will help determine how seasonal flows affect chloride load. The goal is to evaluate how conductivity impacts benthic macroinvertebrate assemblings.