Monitoring and Studies


To ensure that decisions affecting the rivers are based on reliable science and that the changes in management - like wastewater treatment plant upgrades - are effective in improving the rivers' health, OARS monitors conditions on the rivers.

Water Quality, Streamflow, and Habitat (1992 - present): In 1992, OARS started a testing water quality to evaluate the impact of wastewater treatment plant upgrades completed in the late 1980s. OAR volunteers have tested water quality every summer since 1992. Today OARS tests water quality and monitors streamflow and related parameters at mainstem and tributary sites from the headwaters of the Assabet River in Westborough and the Sudbury in Saxonville to the end of the Concord River in Lowell. Water quality and flow data collected under OARS' EPA-approved QAPP may be used by EPA and DEP in making regulatory decisions and was included in DEP's 2001 SuAsCo Water Quality Assessment Report (the most recent SuAsCo report with data).

Annual water quality reports are available on the Water Quality Reports page.

Stream Health Index or how to interpret data: Collecting data is not enough! Read more about what the data means and how OARS' Stream Health Index is calculated to assess overall river health.

Trout Streams: In 2012/2013 OARS collaborated with the Greater Boston Chapter of Trout Unlimited (GBTU), Sudbury Valley Trustees, and USGS Conte Anadromous Fish Labs. Building on the successful efforts of GBTU, the Sudbury Conservation Commission, and MA Fish and Wildlife identifying small trout streams in Sudbury, the project assessed current conditions to identify opportunities to protect these cold-water fisheries.

River Continuity: In the spring of 2010, OARS volunteers surveyed over 70 culverts and bridges in the Nashoba Brook sub-watershed to assess whether they pose barriers to the passage of fish and wildlife. In 2013, as part of the Trout Stream project, OARS volunteers will be surveying culverts and bridges on several small streams in Concord, Hudson, Marlborough, and Sudbury.

Mapping Invasive Aquatic Plants: OARS is surveying invasive aquatic plants on the Sudbury, Assabet, and Concord Rivers to map known invasives, find new infestations, and prioritize and track the progress of water chestnut pulling. In 2013, 2014 and 2016, OARS surveyed all of the mainstem rivers (Sudbury, Assabet, and Concord) for water chestnut as part of the SuAsCo CISMA water chestnut control effort funded by the Nyanza Restoration Fund.

Plant biomass (2005 - present): In August each summer, OARS assesses the mass of aquatic plants growing in the river. This is a long-term effort to measure changes in the aquatic plant biomass in response to the major upgrades to the watershed's wastewater treatment plants completed in 2012.

Endocrine Disrupting Chemicals: In 2010, OARS collaborated with the University of Massachusetts' Professor Arcaro to study the effect of endocrine disrupting chemicals in the Assabet River.

Read more about volunteering with OARS' monitoring program.