Monitoring

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.)

Plant biomass: In 2005, OAR started monitoring the growth of aquatic plants in the river to be ready to measure changes (hopefully for the better) in the mass of plants in the river as upgrades are made to the watershed's wastewater treatment plants.

During the last decade OAR's monitoring program has helped to raise awareness of the Assabet's nutrient problem, pointed to the need for stricter phosphorus limits in the wastewater treatment plant's NPDES permits, made a strong case for the Total Maximum Daily Loading (TMDL) study, and indicated the need for a groundwater model of the Assabet watershed. Water quality and flow data collected under OAR's EPA-approved QAPP may be used by EPA and DEP in making regulatory decisions.

Annual water quality reports and recent data and Stream Health Index readings are available on the Findings and Data page

Read more about volunteering with OAR's monitoring program. Or continue to What do we test.