Water Quality Data – August 2015

August CWMN results revealed higher levels of bacteria due to increased rainfall prior to sampling

August’s Neponset watershed sampling took place on Wednesday the 5th. Our volunteers helped to collect samples from 41 different sampling sites, and the map below shows the bacteria results we received.

CWMN Event Bacteria 08052015


Sampling bottles at site MOB001

Red and orange dots on this map indicate areas along the watershed that are not safe for swimming by the state’s bacteria standards. Particularly high sites this month include UNB016, UNB014, UNB002, PTB047, NER185, MOB001, PUB002, MEB001, GEB020, and NER080, which exceeded the “boat-able” limit as well as the “swimmable” standard.

August’s bacteria were noticeably higher than July’s results, and this was due to the increased amount of precipitation the watershed received in the 72 hours prior to sampling in August.

In July, the watershed received 0.17 inches of rain prior to sampling, while in August, it received 0.26 inches. The timing of the rainfall was also important – in July, rain began to fall on our samplers as they were out collecting, and in August the rain fell about 24 hours before sampling.

Rainfall creates runoff from parking lots, animal waste, etc., which makes its way into the watershed and results in the higher bacteria counts. It takes time for the rain water to carry pollutants to the water bodies, which is why we saw higher bacteria levels in August versus July. From the map, you can see that sites close to densely populated areas, such as Boston, have high bacteria levels due to the increased runoff.


An example of runoff from a road

For a detailed view of the bacteria results, as well as other water quality indicators such as pH, nitrogen, phosphorus, and ammonia, click here.

If you have any questions about the data, or want to become a CWMN Volunteer, please contact Environmental Engineer, Sarah Bounty, at 781-575-0354 x302 or bounty@neponset.org.

Thank you to all of our volunteers who helped with sampling this month!

Meghan Rauber, Intern, August 2015

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