July 25, 2008
Columbia scientists will supply the public with critical data on the river's safety

A common summertime question around New York is: "Is the Hudson River safe to swim?" This has spurred Columbia University's Lamont-Doherty Earth Observatory and the regional nonprofit organization Riverkeeper to carry out a joint study of water quality in the Hudson River. The program is the first to regularly test the water from New York Harbor to the river's upper reaches and to make the data available quickly to the public. It is aimed at pinpointing the processes that affect water quality, and will supply the government with sound science and, ultimately, help protect the public.

Microbiologist Greg O’Mullan processes a sample from the Hudson River with Lamont-Doherty summer intern Liz Suter.
Microbiologist Greg O'Mullan processes a sample with Lamont-Doherty summer intern Liz Suter.

Image credit: Kevin Krajick/Earth Institute

Since the passage of the Clean Water Act in 1972, water quality in most of the nation's rivers has improved greatly, including the Hudson. With the perception that the river is cleaner, people are now using it for recreation in growing numbers. Parts of the river and its tributaries, however, are still sometimes impaired by discharges of raw sewage from aging wastewater treatment systems. Information on fast-changing water quality is not easily accessible, coordinated or timely enough to help the public determine when or where it is safe to enter.

"If someone is going to decide whether to send their child in the water, we need more information, and we should demand more information," said Lamont-Doherty scientist Greg O'Mullan, who is helping lead the research along with his colleagues Andrew Juhl and Raymond N. Sambrotto. "We are trying to provide the link between academic science and practical action."

At a riverside press conference in midtown Manhattan, Lamont-Doherty Director G. Michael Purdy called the Hudson "an iconic example" of the nation's neglected river systems. He called for accelerated fundamental research to understand how such systems work, and to help drive policy decisions.

Patrolling the Hudson with a Riverkeeper boat, in 2006 and 2007, O'Mullan and his colleagues conducted a pilot study, sampling water at 27 sites along the Hudson from New York Harbor to Peekskill, about 40 miles upriver. They measured the sewage-indicating bacterium Enteroccocus, as well as salinity, oxygen, temperature, turbidity and chlorophyll. In May 2008, with funding from the Wallace Foundation, the program added 40 sampling sites, extending from the harbor up to Waterford, some 150 miles north of New York City. The initial report, plus continually updated data, will eventually be posted on Riverkeeper's Swimmable River web pages.

For now, most sites will be monitored once a month. While it is not yet at the stage where it can be used as a guide to safe swimming locales, the program has revealed extreme and surprising variability in water safety, based on location and weather conditions. In particular, sewer overflows, often triggered by rainstorms, can send unsafe amounts of disease-causing organisms into waterways. The findings highlight a number of concerns:

  • There are times and places, particularly near-shore after rainstorms, where counts of bacteria far exceed federal and state standards for recreation.
  • In 2007, 21 percent of samples collected north of New York City had counts of sewage-indicating bacteria that exceeded the federal guideline for contact.
  • In the waterways surrounding New York City, 32 percent of the samples exceeded the federal guidelines for contact.
  • There are specific locations (e.g., the heavily industrial Newtown Creek in Brooklyn) that have chronically poor water quality conditions.
  • Severe storms, even if short-term, can render much of the lower river unsafe for activities such as swimming and kayaking.

Unfortunately, there does not appear to be a simple relationship between rainfall and counts of sewage-indicating bacteria, said O'Mullan. Some areas may meet guidelines for safe swimming a day or two after rain, while others can take substantially longer, especially after heavy rainfall.

For more information, read the complete news release.

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