OARS River Log | By Ben Wetherwill, OARS’ Water Quality Scientist | Published March 7, 2025

OARS has been collaborating with the Green Acton Water Committee over the past several years to study chloride in Nashoba Brook. Prompted by OARS’ call for volunteers to help study rising conductivity and chloride levels that we have been seeing in all our rivers, Kim Kastens has been leading a team from Green Acton and Westford in a study of Nashoba Brook. OARS has been supporting their study with shared equipment and data analytics expertise.

Kim recently presented to the Acton Conservation Commission the findings from continuous conductivity logging that they did in 2024. The presentation was very clear and informative, and the Conservation Commission seemed impressed and eager to continue the study. Green Acton’s data demonstrated that salt concentrations remain high all year round and that groundwater is the primary contributor to these chronic high concentrations. The data showed that concentrations reach particularly high and concerning levels during the late summer and fall when flow and dilution are low. This is concerning because late summer and fall are active periods for the aquatic life in the streams and rivers. Kim shared data from studies showing how chloride can adversely affect algae, zooplankton, and amphibians and talked about how concentrations are approaching critical thresholds.

Here is a link to the presentation slides. OARS is looking for other local groups to do similar studies in other SuAsCo tributaries. If you are interested in studying this question in your neighborhood, please contact our Ben Wetherill, our water quality scientist. To learn more about Green Acton and its environmental activities, visit their website at green acton.org.