Neponset River 2019 Water Quality Summary

Overall, it's a mixed outlook for the Neponset River, with outstanding dissolved oxygen, mediocre total phosphorus, and worsening E. coli levels.


This year the Citizen Water Monitoring Network (CWMN) was made possible by 52 dedicated volunteers, who collected 480 water quality samples at 41 locations from May through October.


Figure 1: A map showing the 2019 CWMN water sampling locations in the Neponset River Watershed.


Watch the 2019 Water Quality Presentation

View water quality presentation by NepRWA Environmental Scientist, Chris Hirsch, and NepRWA Science Fellow and CWMN Manager, Kelly DiStefano. Special additional presentation on PFAS by guest speaker, Steve Rhodes, Massachusetts Water Resources Authority Laboratory Director.


The Data

With multiple tests per sample, we have a LOT of data! Our main parameters, E. coli, total phosphorus, and dissolved oxygen give us a good idea of the health of the Neponset.  We can use them to learn how the water in 2019 compares to the average year. Similarly, it helps us track long term trends in the health of the Neponset River.


For each parameter, (E. coli, phosphorus, and dissolved oxygen) there are standards set by the EPA and the Massachusetts Department of Environmental Protection.  To assess the health of the Neponset, we calculated how often each site met these standards, and divided them into categories as shown in table 1 below.  For example, for the parameter E. coli, if a sampling site met the water quality standard more than 90% of the time, we considered that site to be ‘outstanding’.  If the site met standards 75-90% of the time, we considered it to be ‘good’.   Meeting the standard 50-74% of the time would make that site ‘moderate’, and if a site met the standard less than 50% of the time, it was considered ‘poor’.

Table 1: The range of compliance for water quality data by parameter based on how often a site met water quality standards. 

All categories were determined based on the range of compliance we saw in the data.  To determine what an “average year” looks like in the Neponset River, we took an average of the last 10 years of data and categorized it as described above.


2019 vs. the Average Year

The following graphs provide a ‘snapshot’ of how water quality in 2019  compared to the average year in the Neponset River.  The y axis (vertical) shows the number of sites (out of 41 total) that fell into each category.  The x axis (horizontal) shows the categories for this year vs. the average year.

Figure 2: A graph showing 2019 vs. the average year for E. coli.

Compared to the average year, this year saw an increase in poor and moderate sites, and a decrease in good and outstanding sites.

Figure 3: A graph showing 2019 vs. the average year for phosphorus.

Similarly, total phosphorus didn’t fare much better. We had more poor and moderate sites in 2019 than we typically see. Although the number of good sites also increased, we saw a sharp decline in the number of outstanding sites.  This means that many of the typically outstanding sites fell into poorer categories in 2019.

Figure 4: A graph showing 2019 vs. the average year for dissolved oxygen.

On the other hand, dissolved oxygen was almost the same as the average, with a little improvement.  Figure 4 shows slightly more good and outstanding sites than the average year.


Long Term Trends

E. coli

Now that we have an idea of how the Neponset River did this year compared to an average year, we wanted to if the results were a single year blip, or part of a larger trend. The following graphs show how the water quality has changed over the past ten years.  The y axis shows the number of sites in each category, and the x axis shows the progression of time.  Above the graph are our water quality categories.

Figure 5: A graph showing the long term E. coli trends for the Neponset River. 

The 10 year trend shows that for the parameter E. coli, the number of poor and moderate sites has been steadily increasing .  It also shows a pretty steep decline in outstanding sites, with good sites following a similar trend.  This means E.coli pollution has been getting worse over the past ten years.

Figure 6: A graph showing the difference in bacteria levels during wet and dry weather sampling days. 

Why are we seeing increasing levels of E. coli in the Neponset river? When we look at the variation in bacteria levels on wet weather days vs. dry weather days, it becomes apparent that stormwater pollution plays a large part in increasing our bacteria levels overall.  Increased urbanization in the watershed is a big factor in increased bacteria levels and stormwater pollution.

See these articles for information on what we’re doing to reduce the impact that stormwater pollution has on the Neponset River.


Total Phosphorus

Figure 7: A graph showing the long term phosphorus trends for the Neponset River. 

The total phosphorus trends were a little more messy than E.coli. We’re seeing a steep decrease in the number of outstanding sites, and the number of good and moderate sites are on the rise.  However, the number of poor sites has remained largely the same.  This means that over 10 years, many of our outstanding Phosphorus sites have become just good or moderate.


Dissolved Oxygen

Figure 8: A graph showing the long term dissolved oxygen trends for the Neponset River. 

Thankfully, dissolved oxygen has stayed roughly the same long-term.  We aren’t seeing a big increase in poor or even good sites, and we aren’t seeing much of a decline in outstanding sites.  In other words, this tells us that the majority of our sites have outstanding dissolved oxygen. Most importantly it means they are staying consistently outstanding over the long-term.

In conclusion, it’s an overall mixed outlook for the Neponset River: outstanding dissolved oxygen, mediocre total phosphorus, and worsening wet weather E. coli levels.


What We’re Doing to Fix Water Quality

1). Continuing to monitor the water quality of the Neponset River.

2). Fighting stormwater pollution by building rain gardens.

3). Locating and eliminating pollution sources.

4). Awareness and Education through outreach campaigns and school programs

None of these programs could happen without your continued support. Together we can continue to make a positive impact of the water quality of the Neponset River. Donate Today!


Thank You to Our Volunteers

Finally, the Neponset River Watershed Association is very appreciative of the time and effort given by our CWMN volunteers. We could not continue to monitor the health of the Neponset River and its tributaries without their help.

A big shout out to these tremendously dedicated folks: Craig Austin, Matthew Becker, Rob Belcher, Karen Brenner, Mark Brule, Dave Bryant, Win Burr, Peter Byerly, Jack Campion, Julien Chambert, Jim Cianci, Susan Clare, Daniela Dana, Chris Donovan, Craig Ellis, Chris Fisher, Tammy Fisher, Laura & Chris Garrity, John Hanfeld, Mary Pat Happ, Heaslip Family, Anne Herbst, Doug Holdridge, Kim Johnson, Ardis Johnston, Ruth Johnstone, Jim Kaemmerlen, Peter Kane, Judy Karlin, Taber Keally, Peter Leahy, Betsey McKenzie, Jeanine Meehan, George Mills, John Monahan, Will Nelson, Fran O’Neill, Tom Palmer, Hung Pham, Craig Reise, Michele Rogers, Virginia Ryan, Anne Rydjeski, Jake Sconyers, Rob Scott, Stu Skinner, Mike Smith, Fred Taylor, Lisa Troy, Roger Turner, and Joan Walsh.


Kelly Di Stefano, Environmental Fellow–January 2020

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