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2018 Was One of the Rainiest Years on Record in NYC

Updated: Sep 29, 2020

New York City just experienced its fourth-wettest year on record.

In 2018, 65.55 inches of precipitation fell in Central Park, according to the National Weather Service. That’s more than 15 inches, or 31 percent, above normal.

When we read about this statistic in March, SWIM checked in with our members, NYC Water Trails Association, Bronx River Alliance, Newtown Creek Alliance, and Hudson Riverkeeper to see if the water quality data they collected for 2018 was worse than in recent years. Indeed it was. The reason for the poor water quality is related to the fact that nearly every time it rains, even as little as one tenth of an inch, the City's overburdened sewer system gets overloaded and discharges large volumes of untreated sewage into our waterways. Scroll down to learn more about this and what needs to be done.

We thank our members whose citizen science and water quality testing programs inform NYC's waterway stewards and users about the health of our waterways! The links above in blue provide more information about each of the water quality testing programs and how you can get involved!


The largest ongoing source of pollution in NYC's waterways is combined sewer overflows (CSO): a combination of polluted stormwater from our streets and untreated sewage that discharges into our waterways from the City's sewer system. Currently, the system discharges ~20 billion gallons of CSO into NYC's waterways per year. The diagram below illustrates what happens when the City's combined sewer system overflows and discharges untreated sewage into our waterways.


The City's CSO Long Term Control Plans to address this issue are just getting underway and two are still in the planning stages. You can learn more about the City's plans here. When all the City's plans are completed (sometime between 2030 -2042) the system will still discharge ~18 billion gallons per year into our waterways. While this is a significant reduction compared to the 110 billion that used to discharge into our waters back in 1985,18 billion gallons of raw sewage still poses a threat to public and ecosystem health. Here is a link to a letter we sent to the State about the flawed plans to improve water quality in NYC's waterways by 2030. NYC can do better.

SWIM Coalition members, Hudson Riverkeeper, NRDC, and Save the Sound has recently launched a very informative website on this topic called Cut the Crap NYC! which lists several actions you can take to help improve NYC's waterways. Check it out!


SWIM member organization, Natural Resources Defense Council (NRDC), has been tracking CSO Alerts for NYC (issued by NY Dept. of Environmental Conservation (DEC) under the Sewage Right to Know Program) over the past few years.

The graph below illustrates that increased rainfall correlates directly with increased combined sewer overflow alerts in NYC over the past three years. Here is a link to NRDC's blog post on this topic which states that "New York City experienced sewage overflows, on average, once every 3 days in 2018. That’s a 44% increase from 2016."Sources for the graph: NYSDEC and NOAA

According to the NYC Panel on Climate Change, our region can expect to see a 1 – 8% increase in precipitation by the 2020s, and 4 – 11% increase by the 2050s.


The graph below, generated by Hudson Riverkeeper, illustrates the increase in NYC's precipitation in 2018 (during the recreational season) and compares it with 2017 rainfall during the same period, and includes a reference of rainfall data for 2008, the year that NYC DEP currently uses for all of the City's CSO Long Term Control Plans. When we brought this to their attention at a public meeting in April 2019, they checked the average rainfall over the past 10 years (2008 -2018) and say that the 2008 rainfall data is still a reasonable number to use for their planning. We'll be watching this issue closely to see if that rationale still holds true in 2020. We're not 100 % convinced.

Water quality sampling results from NYC Water Trail Association below show the level of enterococcus bacteria in our waters in 2018 were well above acceptable levels for safe swimming and fishing. Enterococcus is an indicator for fecal matter in a waterway. The waterways listed below are all waters where New Yorkers come into contact with the water for educational and recreational purposes.

Water Sampling results from Water Trail Association

We shared these results with NYC DEP and asked them if they feel the 2008 data are still appropriate to use in the City's CSO Long Term Control Plans. They said yes.

SWIM will follow the water quality results tracked by our members for 2019 and report them here and in our quarterly e-news. Be sure to sign up for our e-news here.

SWIM Coalition will also continue to call on the City and State to improve the CSO Long Term Control Plans, adopt the more stringent water quality standards mandated by the EPA to determine a waterbody's attainment with the fishable swimmable criteria of the federal Clean Water Act, develop policies and programs to incentivize large scale implementation of green infrastructure solutions to manage stormwater in NYC, and to model their CSO Long Term Control Plans based on projected levels of increased precipitation and climate change related sea level rise.

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