Mid-Season CWMN Results

Thanks to the hard work and dedication of our Citizen Water Monitoring Network (CWMN) volunteers we’re now in our 23rd year of monitoring the health of the Neponset River. We’ve successfully completed three months of CWMN sampling, and overall we have mixed results at the midpoint of our year.

15 out of the 42 sites exceeded the maximum E. coli standard for swimming (126 cfus), but only two of those sites also exceeded the boating standard (630 cfus). These results suggest that all of the Neponset River and almost all of the the streams that flow into it are safe for activities like canoeing, kayaking, paddle boarding, fishing, and wading. More than half were clean enough for swimming, although we recommend checking with your local town’s health department before swimming in any local water body. We also typically see a spike in E.coli when it rains because of polluted stormwater runoff, so we recommend staying out of the water for at least 48 hours after a storm. This is also why you should always pickup after your dog. Needless to say, we don’t recommend cooling off in Meadow or Unquity brook this summer!

E. coli Results


Data from the first three sampling months shows that the E. coli levels in more than half of the sites meet the swimming standard of 126 CFUs (colony forming units). 

The 15 CWMN sites with the highest E. coli May-July 2019


Phosphorus Results

Phosphorus is a key nutrient for plants. This is why people add fertilizer to their gardens and yards. Unfortunately, when too much fertilizer is applied it can get washed off when it rains and it ends up in our streams and ponds. Too much phosphorus can cause harmful algal blooms, cyanobacteria blooms, and fish kills.

The EPA has a different standard for ponds and lakes than they do for streams. 29 of our total sites (26 streams and 3 ponds) exceeded the EPA Total Phosphorus Standard. With over 70% of sites are exceeding for phosphorus its clear that the Neponset Watershed has a phosphorus problem. For tips on how to reduce your phosphorus impact on the river visit https://yourcleanwater.org/lawn/

Data from the first three sampling months shows that almost 2/3rds of our sites exceed the EPA Total Phosphorus standard. 




Dissolved Oxygen Results

Dissolved Oxygen has been referred to as the “air” fish breathe under water. If the concentrations of oxygen in the water get too low fish and other aquatic animals that can’t escape can suffocate and die. Excess phosphorus is a key driver of low levels of dissolved oxygen, which is why we closely monitor both parameters. Dissolved Oxygen has been looking good this season, with only 6 sites failing to meet a healthy DO level of above 5.00 mg/L.

Data from the first three sampling months shows that most of our sites have healthy levels of DO, while only 6 sites fail to meet our desired standard of 5.00 mg/L.

Once the Sampling season comes to an end in October, we will be able to get a more accurate picture of the bacteria, dissolved oxygen, and other nutrient levels within our watershed. If you have any questions, please contact Kelly Di Stefano at distefano@neponset.org

Thanks again to all of the dedicated volunteers who sacrificed their mornings to help us take water samples all over the Watershed!

Kelly Di Stefano, Environmental Fellow — August 2019




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