Initial Findings

The Water Quality Testing Program aims to characterize the complex water quality conditions in the Hudson River Estuary. Our initial findings show overall water quality to be highly variable depending on both site, location and time sampled. This study is ongoing and as the data increase, a better picture of problem locations throughout the estuary will emerge.

The initial findings are as follows:

• Water quality was highly variable through time at nearly all sampling locations. Every station had acceptable Enterococcus counts in some samples, but almost every station also had some samples with unacceptable counts. Most stations had unacceptable Enterococcus counts on 10-30% of the dates sampled.
• Stations near the shore (where recreation is most likely) and in tributaries were more frequently contaminated than those in the middle of the Hudson main channel. When contamination was found near the shore and in tributaries, water quality was often very poor. Maximum Enterococcus counts at such stations were at least 10-20x the federal guidelines for swimming.
• Contamination “hotspots,” locations that were frequently contaminated, were found throughout the estuary. Twelve of 77 stations had unacceptable Enterococcus counts on more than 40% of dates sampled, and 5 of those stations had unacceptable counts on at least 50% of dates sampled.
• Contamination was often local, in that unacceptable Enterococcus counts at a station did not necessarily mean that other nearby stations were also contaminated. This suggests that the contamination measured was frequently related to local sources.
• Rainfall increased the likelihood of finding sewage contamination, however, the relationship between Enterococcus counts and rainfall was complex. Rain did not always lead to elevated counts and elevated counts were also found at many stations at times when rain had not occurred in the days before sampling. The duration of contamination following rainfall was also variable.
• Widespread contamination (occurring at many stations simultaneously) was found after unusually-heavy rainfall events.
• Urbanization did not necessarily reflect the likelihood of sewage contamination. For example, the frequency of unacceptable Enterococcus counts was very similar between the waters around Manhattan, the Tappan Zee, and the freshwater region between West Point and Waterford.
• Our results are consistent with the long-term trend of improving water quality in the Hudson. Most places we have sampled have acceptable water quality (at least, in terms of sewage contamination) most of the time. That is good news. However, most sites were found to have unacceptable conditions some of the time, and ‘hotspots’ of frequent contamination were also found. Given increasing recreational use of the Hudson in all regions, combined with high variability in water quality, increased testing and public notification are recommended. Improved water quality management would better protect public health and maximize the social and economic value of the Hudson River Estuary.