June 2020 Water Quality Report (CWMN)

Data collection continues as water quality takes a typical June decline.

Over 50 volunteers recently took water samples as part of NepRWA’s Citizen Water Monitoring Network (CWMN). Sampling in the wee hours of the morning can lead to all kinds of discoveries including a snapping turtle laying her eggs by Ponkapoag Brook!

E. coli Results

E. coli is a bacteria that often indicates contamination from human and animal waste, including dog waste that is left on the ground. The bacteria associated with this waste can make people sick.

In June, only 53% of samples met the EPA swimming standards and 10% of the sites sampled had E. coli levels that were unsafe for recreation, therefore we don’t recommend splashing around in Unquity Brook this summer!

Residents can help reduce the amount of E.coli bacteria in the water by always picking up after your dog and throwing the waste in a trash can — and by making sure that your septic system is working properly. The E. coli results are summarized in the map and graph below.



How do these results compare to past years? The graph below shows the June 2020 results compared to the previous nine June results from days when sampling was completed after dry weather.

The colored bars represent the percentage of samples that met different water quality standards. Only half of the samples meeting the swimming standard, which is not uncommon for the Neponset Watershed at this time of year.

Phosphorus Results

Phosphorus is a key nutrient for plants and is a large component of most fertilizers. Unfortunately, when fertilizer washes off lawns it can end up in streams and ponds. Too much phosphorus can lead to harmful algal blooms, cyanobacteria blooms, and fish kills.

In June, only 5 of the 40 sites tested had healthy levels of phosphorous, which is not good for water quality in the Neponset River.

The reduction of phosphorus is critical to the health of our waterways and we encourage homeowners to do their part through the proper application of lawn fertilizer. Learn how you can help at www.YourCleanWater.org/lawn


Dissolved Oxygen Results

Dissolved oxygen has been referred to as the “air” fish breath underwater. If the concentrations of oxygen in the water get too low, fish and other aquatic organisms can not survive. Low dissolved oxygen is often the result of too much decomposition of algae caused by excess nutrients in the water body.

80% of the sites sampled had water with healthy levels of dissolved oxygen. This is good news for most fish and aquatic insects. However, fish living in Pequit Brook, Mill Brook, Spring Brook, and the most upstream reaches the Neponset are packing up their bags and moving to streams with more dissolved oxygen. The results are summarized in the map and graph below.



Follow this link to a list of CWMN site descriptions.

Thank you to all the dedicated volunteers who make up the backbone of the CWMN program! If you have any questions about the CWMN results please contact NepRWA Environmental Fellow, Declan Devine, at devine@neponset.org

One response to “June 2020 Water Quality Report (CWMN)”

  1. Carey says:

    In future newsletters, please let us know where it IS safe to swim in the watershed.

    Thank you

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