WESTPORT — A recent water quality study, which included testing rivers in Westport and Weston, has yielded some alarming results.

The 2019 Fairfield County River Report, released in December by Harbor Watch, the water quality research program based out Westport’s Earthplace, monitored 16 rivers in 16 towns for bacteria — like E. coli and Enterococci bacteria — that can indicate sewage pollution in freshwater and saltwater systems. Of the 123 unique sampling locations that were monitored 10 times among the rivers, 77 percent exceeded either one or both of the state criteria for acceptable levels of bacteria.

Muddy Brook and Pussy Willow Brook in Westport, and Sasco Brook (Westport, Fairfield, Easton) were among a five-way tie for having the most sites that failed in the study. Of the test sites conducted at Muddy Brook, Sasco Brook and Pussy Willow Brook, each one failed in terms of bacteria levels.

The Saugatuck River, which had test sites in Westport, Easton, Weston, Norwalk, Danbury, Ridgefield, Bethel, Redding and Wilton, had a failure rate of 56 percent, while the Norwalk River (New Canaan, Norwalk, Redding, Ridgefield, Weston, Wilton) posted a failure rate of 73 percent.

“Quantifying bacteria in our waterways and locating potential sewage pollution sources in the Long Island Sound watershed is critically important for the health of both the people and the enviorment,” said Dr. Sarah Crosby, the director of Harbor Watch. “We are grateful for the support of our municipal partners in Greenwich, Stamford, Darien, New Canaan, Norwalk, Westport, Fairfield, Stratford, Bridgeport, Wilton and Ridgefield as we we work jointly with them to find and fix these pollution sources.”

Besides testing each river for bacteria, Harbor Watch’s research team tested the waters for dissolved oxygen, temperature and conductivity.

Dissolved oxygen is a significant water quality indicator, since numerous aquatic species rely on it to survive. Conductivity measures how easily the water can carry an electrical current; temperature is a key aspect for aquatic species, which can move from a certain location, if the temperature is too high, or too low.

Muddy Brook is of particular interest to Westport, since it discharges into the Sherwood Island Mill Pond — a popular destination for swimmers and fishing, especially shellfishing. Six sites were monitored by Harbor Watch from May until September and each one exceeded at least one of the state Department of Energy and Environmental Protection’s E. coli criteria. The DEEP geometric mean for E. coli rose in five of the six sites from 2018. Regarding the dissolved oxygen test, none of the six sites at Muddy Brook failed.

Sasco Brook, which discharges into Long Island Sound at Southport Beach, also had six sites tested, all of which failed the DEEP E. coli criteria. However, the bacteria levels in three of the sites decreased from 2018 and all sites at Sasco Brook passed the dissolved oxygen test.

The Norwalk River, which is about 20 miles long and discharges in Norwalk Harbor, has been monitored by Harbor Watch for more than 20 years. Of the 10 sites tested, eight failed the state’s criteria for E. coli, and all but one site passed the dissolved oxygen study.

With a watershed of approximately 38,704 acres, the Saugatuck River has been monitored by Harbor Watch for more than a decade. The study indicated nine of the 16 sites tested failed the state’s bacteria criteria. None of the sites failed the dissolved oxygen criterion.

The report notes two sewage spills in the harbor, which were reported by Westport in August, may be the cause of elevated Enterococci bacteria levels in the Saugatuck River early on during the monitoring process.

Pussy Willow Brook, situated entirely in Westport, was tested by Harbor Watch from May through September last year for the first time since 2011. Previously, the brook was monitored outside of the May-September season. All five sites exceeded the E. coli criteria in 2019, but dissolved oxygen values met the minimum criterion at each site.

Other Fairfield County rivers tested included Belden Hill Brook (Wilton), Bruce Brook (Stratford, Bridgeport), Comstock Brook (Wilton), Deep Brook (Newtown), Farm Creek (Norwalk), Horseneck Brook (Greenwich), Noroton River (Stamford, Darien, New Canaan), Pequonnock River (Monroe, Trumbull, Bridgeport, Shelton, Newtown), Pootatuck River (Easton, Monroe, Newtown), Rippowam River (New Canaan, Ridgefield, Stamford), and Silvermine River (Norwalk, New Canaan, Wilton).

Each river was visited twice a month by Harbor Watch from May to September. Belden Hill Brook and Silvermine River had the lowest percentage of sites that failed the bacteria criteria, at 50 percent. Each of the river’s sites passed the dissolved oxygen test. The Saugatuck River was next with a 56 percent failure rate (bacteria criteria), followed by the Pequonnock River (63 percent).

“Cleaning up these rivers and streams is a priority for the leadership and residents of these towns,” Crosby said. “We look forward to expanding our research to work with our impacted towns. While these data show that there is much work to be done, I am optimistic that we will see improvement in many of these watersheds through the committed work of local residents and the municipalities to fix these problems.”