Winter has begun and along with it the annual practice of treating the roads with salt to reduce icing. Salt eventually washes away and when this happens, it quickly dissolves and flows into numerous wetlands, streams and the Ipswich River. The use of road salt has increased in the last 10-20 years and it is known to impact aquatic life, so volunteers collect data to understand trends in salt concentrations and what this means for the Ipswich River.
Volunteer water monitors are collecting data on chloride levels showing clear trends on where road salt is present in the Ipswich River and tributary streams. In general, sites downstream of highways show high concentrations approaching levels harmful to aquatic life and sites further from developed areas, and with more protected lands show levels considered healthier. Chloride levels are highest in the upper watershed areas of Wilmington and Reading near I-93, where the highway combined with the greater road network of this area creates more stormwater runoff to the watershed. At many sites, chloride levels do not change that much even in summer, indicating that salts stay in the watershed for a long time and do not simply wash away in the spring.
Finding ways to reduce salt use while keeping roads safe will benefit the river and communities that depend on it for water. Different parts of the country are trying salt alternatives like sugar beet juice, and locally, things like better salt storage and training can help, but road salt is still an emerging challenge to the health of the river that will not reverse soon. Volunteer monitors will continue to collect data on this emerging threat so we can protect the river.