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Water quality report: one-third of ponds tested on Cape Cod called ‘unacceptable’

This map produced by APCC reveals the location of embayments with 'unacceptable' water quality.
This map produced by APCC reveals the location of embayments with 'unacceptable' water quality.

One-third of ponds and nearly 90 percent of embayments on the Cape had ‘unacceptable’ water quality in 2020, according to the Association to Preserve Cape Cod’s third annual State of the Waters report, which also revealed the first-ever less-than-perfect score for a community’s drinking water supplies.

The report, which grades water quality based on existing data compiled over years of water sampling and monitoring, found that the degradation in marine and freshwater environments is largely due to fertilizer use, stormwater runoff, and inadequately treated wastewater from septic systems.

“Septic systems result in nitrogen and phosphorus being discharged directly into our groundwater, which feeds our freshwater ponds and estuaries. And that is the primary driver of water quality,” said Andrew Gottlieb, executive director of APCC.

For the third straight year, about one-third of the ponds sampled had unacceptable water quality, based on data collected from APCC’s cyanobacteria monitoring program in addition to the standard Carlson Trophic Index, which is used to determine the status of pond water quality using data on total phosphorus, chlorophyll and water clarity.


Although the number of ponds studied in the 2021 report increased to 109 from 93 the previous year, the percentage of ponds with unacceptable water quality in the 2019, 2020 and 2021 State of the Waters reports remained relatively consistent at approximately one-third.

But Gottlieb said more monitoring is necessary to develop a clearer picture.

“With nearly a thousand Cape Cod ponds, the small number of ponds where water quality data is available underscores the need to significantly increase the Cape’s freshwater pond monitoring efforts,” said Gottlieb. APCC is calling for the Assembly of Delegates and Barnstable County Commissioners to move forward in approving the Cape Cod Commission’s proposal to study more ponds in 2022.

Of the embayments tested, 87 percent had unacceptable water quality, an increase in the number and percentage of unacceptable waterbodies in previous years.

“Forty-one of the 47 embayments that we analyzed had unacceptable water quality,” Gottlieb said. “Every single south-facing embayment is unacceptable and every west-facing embayment is unacceptable. The only acceptable embayments were north-facing, looking onto Cape Cod Bay.”

In this year’s report, no embayments moved from an unacceptable to acceptable grade, and only six of the 47 graded embayments were determined to have acceptable water quality, representing just 13 percent.

To improve water quality, APCC is calling for towns and homeowners to reduce their nutrient loads by limiting fertilizer use, managing stormwater runoff, and prioritizing sewer infrastructure.

APCC is also encouraging Cape Cod towns to move aggressively in taking advantage of new federal and state funding opportunities for wastewater infrastructure investment.

One bright spot, Gottlieb said, is that 13 of the 20 drinking water suppliers on the Cape continued to receive excellent scores relative to state and federal water quality standards around bacteriologic contaminants. Six were considered good, but one community, Wellfleet, received a poor water quality score.


“They had repeated incidents both coliform exceedance and an E. coli bacteriological exceedance in their finished water that resulted in the need for an order to boil water prior to consumption for consumers,” Gottlieb said.

The Wellfleet Board of Water Commissioners did not immediately respond to a request for comment.

The drinking water score for next year’s report will factor in new state regulations for PFAS — the “forever chemicals” recently detected in drinking water supplies across several Cape towns.

“It is entirely likely,” Gottlieb said, “some of those results will show up as problems in [some communities’] scoring and will reflect in some decreased grades for some of those suppliers.”

Eve Zuckoff covers the environment and human impacts of climate change for CAI.