Site snapshot

Prospect Park Lake

Prospect Park Lake · Prospect Lefferts Gardens · Brooklyn

High contamination levels
Start hereLikely high contamination levels today

Current weather-based estimate: 440 MPN. Latest lab result was 187 MPN on Sep 10, 2026.

How rain usually changes this siteOften rises after rain

Historical medians: 555 MPN in drier conditions and 727 MPN in wetter conditions.

Typical bacteria level546 MPN

Middle lab-measured result across the site's full imported history.

Highest recorded spike24,196 MPN

Highest lab-measured bacteria level in the imported record for this site.

How to read this site

Enterococcus is a group of bacteria that normally lives in the intestines of people and animals. When it shows up at higher levels in the water, it can be a sign that sewage or other fecal contamination has reached that area.

It is used as an indicator organism, which means it helps flag the chance of sewage-related contamination without measuring every harmful thing directly. That makes it a useful way to track bacteria-based water quality conditions across many sites over time.

Lower numbers usually mean cleaner conditions for recreation. Higher numbers suggest elevated or high contamination levels, especially after rain.

MPN stands for Most Probable Number, a standard lab estimate of how much bacteria is present in a water sample. On this site, 35 MPN / 100 mL is the main reference point used to compare lower contamination levels with elevated results.

This is still only one part of water quality. These readings do not measure every form of pollution, and a single sample only captures one moment in time.

Today, based on recent rain

Best guess for the water right now

Likely high contamination levels

Rain sometimes matters here, but the pattern is weaker than at the most rain-sensitive sites. Among this site's historical samples, drier conditions had a median of 555 MPN and wetter conditions had a median of 727 MPN.

Estimated bacteria level440 MPN

This estimate blends recent rain with the site's history. Below 35 MPN / 100 mL is the site's main cutoff for lower contamination levels during swimming or wading.

Threshold35
Estimate440
035140+
Why this estimate looks like it does440 MPN

Based on this site's longer-term pattern plus recent rain near the shoreline.

Recent rain (24h)0.00 in

Most recent rain near this site.

Recent rain used (48h)0.00 in

This is the main rain window used in the estimate.

Water temperature75.4°F

Open-Meteo Marine · Sep 17, 2026 8:00 PM

How rain usually changes this site

Typical in drier periods
555 MPN
54 samples
Typical after wet periods
727 MPN
55 samples
Recent rain signal
Light
Earlier rain signal
Light
History used
195

Recent rain events

  • Sep 13, 2026 1:00 PM0.03 in over 1 hour
  • Sep 13, 2026 11:00 AM0.04 in over 1 hour
  • Sep 13, 2026 9:00 AM0.23 in over 2 hours

How to read this

This is a weather-informed estimate, not a fresh lab result. It is meant to be an early warning for how the water may feel today between sampling dates.

It is not an official beach-opening decision. Use it to judge whether recent rain likely pushed contamination levels higher than usual at this site.

Historical trend

Bacteria level and rain on sampling days

Jul 2021 to Sep 2026

High contamination levels are common here, especially when sampling followed rain.

Lower is better. Colored bands show lower, elevated, and high contamination levels, and blue bars show rain on that sampling day.

Reading this site

Lower contamination levels are usually better for swimming or wading. A single sample only shows one moment, so the longer record is most helpful when you compare dry-weather periods with rainy ones.

Latest lab-measured bacteria level: 187 MPN. Latest lab sample: Sep 10, 2026. Rain on that sampling day: N/A.

Imported samples in 2026: 15.

Site notes: Interstate Environmental Commission

Sampling partners

  • FALSE
  • Billion Oyster Project's Williamsburg Field Station
  • NA
  • Interstate Environmental Commission

Advanced sampling details

Site ID
063
NYS water class
B
District council
39
Sewershed
Owls Head
Rain gauge
BROOKLYN 2.4 SW, NY US
Tide station ID
8517921