On June 10, 2018, the Green Acton Water Committee welcomed Sue Flint, staff scientist for Organization for the Assabet, Sudbury, and Concord Rivers — OARS — as a guest speaker at our regular monthly meeting. Sue directs the OARS water quality monitoring program, which sends citizen scientists out onto the three rivers and their many tributaries to measure in situ water properties and take water samples for laboratory analysis. Two of OARS’ sampling sites are in Acton: one on Nashoba Brook off of Wheeler Lane, and one on the Assabet River at the Acton Canoe Launch.
Sue’s talk began with an orientation to the three rivers, and then walked us through OAR’s findings on habitat and water quality. Here is the full set of slides from Sue’s presentation, although the slides alone cannot convey the lively discussion and Q&A that accompanied Sue’s presentation.
- Overview of the watershed
- Assabet River (large file)
- Sudbury & Concord Rivers, and tributaries (large file)
Probably the most exciting finding, from an environmentalist point of view, was the success story of phosphorous in the Assabet River. Phosphorous enters rivers by runoff from fertilized lawns and fields, and in the discharge from wastewater treatment plants. Excessive phosphorous in fresh water systems enables explosive growth of plant life, which then falls to the river or pond floor and decays.
Powdermill Impoundment of the Assabet River in Acton in 2002
This process, called eutrophication, consumes dissolved oxygen in the water, degrading the habitat for fish and other animal life, especially in the slow-moving water in the impoundments behind dams. Four wastewater treatment plants discharge into the Assabet River: one each in Westborough, Marlborough, Hudson, and Maynard.
Watersheds of the Assabet, Sudbury and Concord Rivers. Wastewater treatment plants that discharge into the rivers are shown as triangles.
When OARS began its water quality monitoring program on the Assabet River in 1992, there was little-to-no effort to remove phosphorous from wastewater. As part of a nationwide cleanup of discharge from wastewater treatment plants (WWTPs) during the 1990s, the plants along the Assabet began to treat for phosphorous, first focusing on summer removal and then expanding to year-round removal.
By 2012, all four Assabet WWTPs were discharging at less than 0.1 mg/L total phosphorous. Total phosphorous level in the river dropped precipitously, and has stayed below the eutrophication threshold range (red line of graph below) for the last five years.
Total phosphorous data from OARS’ citizen scientist sampling program for July and August.
OARS data were essential in making the case for upgrading the Assabet WWTPs, and in documenting the subsequent success. The work is not yet done: levels of nitrogen, another plant nutrient, are still high, and there is still a dense carpet of aquatic plant life in some of the impoundments. But there is plenty of reason to celebrate this victory for citizen involvement in local environmental protection.
All residents of the SuAsCo watershed benefit from OARS’ patient but persistent work in science, advocacy, education, and stewardship. If you would like to learn more or get involved, OARS offers education programs for children and adults and a variety of short- and long-term volunteer opportunities. OARS water quality data and samples are collected by lay people, working under Sue’s careful professional supervision. Volunteers retrain annually to follow sampling protocols and chain of custody procedures that allows the data to be used as evidence in policy making. Green Acton Water Committee members Lucy Kirshner and Kim Kastens are OARS water quality volunteers, and new volunteers for this program are recruited and trained each spring.