Water Quality

In 1992, OAR 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. Over the years, we have updated our methods, improved our data handling, and increased the number of sampling sites. In April 2000 the EPA approved OAR’s sampling methods as documented in the program’s Quality Assurance Program Plan (QAPP). Today OAR tests water quality and monitors streamflow at mainstem and tributary sites from the headwaters of the Assabet River in Westborough to the end of the Concord River in Lowell. (View map of sampling sites.) The overall heath of the river and smaller streams is evaluated using Water Quality and Stream Health Indices. (Read more about OAR's Stream Health Index.)

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