Water Quality Monitoring



The North & South Rivers Watershed Association has been sampling water quality for 23 years to evaluate the health of the rivers. This volunteer-driven program monitors the rivers every other week from the beginning of June to the end of August. Our volunteers monitor for both swimming and shellfishing standards, each of which have specific concentrations of fecal coliform and enterococci bacteria that are considered safe for these kinds of human interactions with the water.

For the sampling date of August 24th 2016, Cornhill Lane and both South River sites (Willow Street Bridge and Julian Street Bridge) were over bacterial standards for safe swimming of 400 cfu/100mL, although Cornhill Lane was just at the standard with 400 cfu/100mL. The South River sites were well over the standard with 1500 cfu/100mL at Willow Street and 2800 cfu/100m at Julian Street. However, the enterococci concentration at Julian Street was 9 cfu/100mL, well under the standard of 104 cfu/100mL. Enterococci is the accepted standard for swimming water quality in brackish and marine waters, however we continue to test fecal coliform due to its use as the shellfishing standard. The observed difference could be due to a number of factors, including environmental conditions causing different growth and survival rates and inherent natural variability. Fecal coliform counts and enterococci counts do not correlate with each other since they are different groups of bacteria. Increases in bacteria counts typically occur when rainfall flushes discharge into waterways. However, since there was no rainfallwithin 48 hours of the sample collection, the higher fecal coliform counts seen are likely due to other factors, one of which may be the favorable growing conditions provided by the recent warm temperatures.

Otherwise, samples from the remaining 8 sites met both the swimming and the shellfishing standards. Shellfish bed sampling sites include North River Marine, Damon’s Point, and the North River Mouth.  The shellfish beds are seasonally closed from June 1 and will reopen on November 1 because water quality in the closed months does not consistently meet the shellfishing standards.

The purpose of the program is to provide the public with information on the water quality status of our rivers and provide data to support eliminating sources of pollution in the rivers. During the summer, our water quality data is published in the local newspapers.

Riverwatch Data – August 24, 2016

Bacterial Source Tracking

In addition to our annual summer Riverwatch program, we have also conducted targeted sampling to track down pollution sources, typically in conjunction with efforts to implement stormwater remediation projects. In 2009 and 2010 we conducted a bacterial source tracking project in Marshfield to understand bacterial contributions to the South River. The NSRWA, MassBays, and our interns collected bacteria samples from the South River and analyzed them at the Cohasset Center for Student Coastal Research. The sampling was conducted iteratively – the sampling locations changed for each round based on what was found in the previous round. With each round (3 wet and 3 dry), we were able to isolate a few areas by the end that could be sources of high bacteria and candidates for stormwater remediation.

Volunteer: Students, parents, retirees – all are welcome to join us each summer to monitor the health of our rivers. Training for participating in our annual water quality monitoring program is held in early June every year. To sign up and for more information call Sara at 781-659-8168 or e-mail sara@nsrwa.org. The sampling typically takes about 3 hours and you must have your own transportation. We try to pair an experienced volunteer with anyone new so you won’t be out there on your own. Thank you for your interest in monitoring with the NSRWA. Click here to sign up to be a Riverwatch volunteer.