Last week marked the conclusion of the thirty-fourth year of NSRWA’s RiverWatch Water Quality Monitoring program. RiverWatch is a volunteer-driven effort that monitors local waters for compliance with both swimming and shellfishing water quality standards. Since 1994, we have monitored bacteria and other water quality indicators like temperature, dissolved oxygen, salinity, and conductivity at ten sites in the North and South Rivers every other week from June through August. We use this data to document the long-term health of our waters, to inform government agencies about the quality of our waters and advocate for improvements where needed.
We kicked off the season on June 17th with a training session for new volunteers. The training consisted of touring the watersheds in NSRWA’s van to conduct a full round of sampling at all sites. For the rest of the summer the new volunteers joined some of our more experienced, long-running volunteers to conduct the sampling. During each sampling session, volunteers drive to each of the 10 sampling sites to collect water quality measurements and samples. At some locations this can require moderately challenging access to sampling sites (steep riverbanks, unstable footing, etc), so our volunteers have to be a hardy bunch!
At the completion of sampling, our volunteers bring the samples to the laboratory at the Cohasset Center for Student Coastal Research (CSCR). CSCR graciously lets us utilize their facility and laboratory equipment, to analyze these samples. This provides substantial cost savings and greatly improves the turnaround time for results as compared to a private lab. Our interns then take it from there. They follow a standardized procedure to analyze the samples. The final result is determined approximately twenty-four hours after initial processing.
NSRWA follows standard Massachusetts protocols for sampling and analyzing indicator bacteria to determine water quality. Indicator organisms have characteristics and life cycles that are similar to those of pathogens, which are organisms capable of causing disease in humans. Since measuring pathogens directly in water can be challenging, indicator organisms are used to estimate the likelihood of pathogen presence due to fecal contamination. Enteric bacteria, a type of indicator organism found in the intestines of warm-blooded animals and humans, are commonly linked with fecal contamination. The bacteria typically used as indicators to monitor both marine and freshwater water quality are Enterococci. According to Massachusetts’ swimming standards, Enterococcus levels may not exceed 104 cfu per 100mL of water sampled.
In addition to Enterococci, at our more marine sites we also test for fecal coliform. We conduct this test in areas that are known to support shellfish. The Massachusetts Division of Marine Fisheries (DMF) tests shellfish growing areas for fecal coliform bacteria to ensure public health and protect consumers from waterborne illnesses. Our rivers are closed to all shellfishing during summer months anyway, but we conduct these tests to track the long-term status of fecal coliforms in these areas. The DMF shellfishing standard is 14 cfu per 100mL of fecal coliform.
This year, we reported our biweekly water quality results on our Water Quality Monitoring web page. An interactive map of the sampling sites and results can be seen on that page. We share this data with the public with a few important caveats; we are not a regulatory agency, and these data are only a snapshot of the water quality at the time they were taken, which was at least 24hrs prior to reporting. Rain and other polluting events can impact the quality of the water at any time.
Indicator water quality results are impacted by a variety of environmental and human factors. Levels often rise after rainfall events when stormwater runoff carries fecal contamination from wildlife, pets, and failing septic or sewer systems into waterways. Warmer water temperatures can also encourage bacterial persistence, while tides and streamflow influence dilution and transport. In addition, land use patterns such as dense development, impervious surfaces, and agricultural activity can increase nutrient and bacterial inputs, further elevating concentrations. These natural and anthropogenic influences create variability in enterococcus results and make it challenging to interpret the “why”.
Some results are readily apparent. Enterococcus concentrations tend to be higher in the upper portions of the watersheds. On the South River, samples collected at the Keville Footbridge (behind CVS) routinely show Enterococcus concentrations that are more the 100x the swimming standard. Detailed source tracking would be required to definitively identify the sources. However, there are several common culprits at this location including considerable dog walking and inputs from heavily developed areas. In the North River, again it is the upstream sites that tend to have higher concentrations. Here the sources may be less obvious with a mix of human and wildlife uses throughout the area. At the downstream sites, in the more tidal sections of the river, results are typically below the swimming standard. The Scituate Wastewater Treatment Plant is a unique sampling location. In cooperation with the plant operators, we collect a sample directly from the discharge stream. The results here are always very low or undetectable. We consider it a great success to have such a well-run plant in place of old, uncontrolled septic systems.
Since we have started sampling, the percent of bacterial samples that have exceeded the swimming standard each summer has decreased, from 22-24% in the 90s and 2000s to 15% in the 2010s and 2020s. This is due to a reduction in stormwater pollution as well as increased sewering along the South River that reduced wastewater pollution. The current results show that there is still work to do in identifying and reducing pollutants in our rivers. You can visit our RiverWatch page for additional data and long-term trends. Also consider volunteering for RiverWatch 2026! You can see all of our Citizen Science opportunities here.
NSRWA and the Massachusetts Bays National Estuary Partnership (MassBays) would like to extend our gratitude to the Cohasset Center for Student Coastal Research for allowing us to use their laboratory for sample processing, as well as to the Norwell Women’s Club and our members for providing funding for this program.
