Healthy waterways are important for both aquatic life and humans who use the water for recreation.

We measure the quality of harbor water through two key indicators:

• Dissolved oxygen is essential for most aquatic life. Coastal habitats and ecosystems thrive in environments with high concentrations of dissolved oxygen.

• Concentrations of fecal coliform bacteria and Enterococci bacteria. Higher levels of these bacteria can mean there is sewage-related water pollution. Though most of these bacteria do not cause disease, higher concentrations can indicate the presence of pathogenic (disease-producing) bacteria.

How we monitor harbor water quality

Water quality standards are set by New York State and monitored by the NYC Department of Environmental Protection (DEP) annually through the Harbor Survey. The Harbor Survey Program has grown to include 40 sites throughout New York waters. Department of Environmental Protection scientists sample these sites weekly during the summer season (May - October) and monthly during the winter season (November - April).

New York’s harbor water quality today

Bacteria levels show that water meets minimum standards

Since the 1990s, average harbor-wide surface water fecal coliform levels have been well below the state maximum standard for fishing and boating (2,000 cells per 100mL, from 5+ samples) and bathing and other recreation (200 cells per 100 mL from 5+ samples).

Since the NYC DEP began monitoring enterococci in the early 2000s, levels have remained below the state maximum standards. Short-term spikes in bacteria may occur after heavy rain.

Dissolved oxygen levels show that water exceeds minimum standards

NYC DEP reports the open water summer average levels of dissolved oxygen harbor-wide, from surface and bottom water, every year. Levels above the state minimum standard (5.0 mg/L) indicate a harbor suitable to most aquatic life forms. Since the 1990s, the annual summer average for surface and bottom water dissolved oxygen levels of open water sites have been above New York State standards.

For more information on harbor quality, please visit the most recent report from the NYC DEP Harbor Survey Report. For information on current beach water quality, please visit DOHMH’s beach water quality map.

There are many schemes of neighborhood boundaries (or geographies) available for different datasets. These include:

• Citywide
• Borough
• United Hospital Fund 42 (UHF42) and United Hospital Fund 34 (UHF34) neighborhoods
• Community Districts (CD), and, related, Community District Tabulation Areas (CDTA)
• Public Use Microdata Areas (PUMA)
• Neighborhood Tabulation Areas (NTA)

We try to make data available at as fine a geographic resolution as we can. Read more about different geographies at this data story.

It would be convenient if each dataset could be made available at the same geography, but this is not always possible. The neighborhood boundaries available depend on the specifics of the underlying dataset.

When we have multiple years of data, we show the data as trend charts.

Trends for individual neighborhoods tend to be very unstable (or "bouncy"), due to small counts for outcomes in individual neighborhoods. To show clearer trends, we usually aggregate up and show trend data by Borough.

Options on some indicators let you compare this indicator to other similar indicators.

We try to make data available as soon as we can.

Many datasets take a long time to reach us — a "lag" of several years, during which data are gathered from different entities to try to create a complete dataset; data are processed (cleaned, deduplicated, etc), and analyzed. It can take several years to prepare a dataset — so a dataset that is several years old is sometimes the most up-to-date information available. Still, this data continues to show us valuable trends and insights.

We also try to display datasets that have been available for many years. Some datasets (like those that are asked on surveys) are not asked every year of the survey, which means that we cannot provide annual data.

For some datasets, we have to aggregate time periods in order to break down data by borough or neighborhood.

Measures are the numeric ways that a dataset (or indicator) are expressed. Examples of different measures might be: number, percent or rate.

A number tells us how much of an outcome is in a certain area. But a rate (usually expressed as, for example, 40 per 100,000) tells us how much of an outcome there is, relative to the population of the area in question. This lets us compare neighborhoods of different sizes.

On this site, we try to show how environmental factors might be connected to health outcomes. One way we do this is with Correlates. We choose potentially-related datasets and display them on a scatterplot so you can see how these two datasets are correlated.

The Disparities view displays neighborhoods by poverty category to show underlying disparities in the data.

Read more about correlation here.