Healthy Swimming Mapper

Use the map to find current advisories and alerts for fecal bacteria or cyanobacteria during the swim season.

Up-to-Date Healthy Swimming Alerts, Advisories and Warnings

Current fecal bacteria advisories and cyanobacteria warnings and alerts issued by NHDES are posted and updated on this map DAILY.

Map Navigation Tips:

  • On a mobile phone, click arrow buttons on the bottom of the screen to switch between different types of advisories.
  • Click on the side dashboard to view the list of current advisories and alerts.
  • The pop-up window will show advisory information, sampling results, photos and historical reports for a beach or waterbody.
  • Use the search bar on the top right corner of the map to find your local waterbody or beach. (Best to search using the town name and include “lake” or “pond.”)

Beach Inspection Program

The Beach Inspection Program monitors public beaches for the presence of fecal bacteria from Memorial Day through Labor Day. A beach advisory is issued when a water sample contains fecal bacteria levels that exceed the state standard, indicating unhealthy swimming conditions. Enterococci is used as the indicator fecal bacteria at coastal beaches while E. coli is used at freshwater beaches.

A coastal beach advisory is issued if 1 sample exceeds 104 MPN/100 mL.

A freshwater beach advisory is issued if 1 sample exceeds 158 MPN/100 mL or 2 samples exceed 88 MPN/100 mL.

Once an advisory is issued, resampling will occur the following day and will continue until the fecal bacteria levels do not exceed the state standard.

Cyanobacteria Harmful Algal Bloom Program

The Cyanobacteria Harmful Algal Bloom Program monitors waterbodies when a potential cyanobacteria bloom is reported by a member of the public. A cyanobacteria advisory is issued lake-wide when cyanobacteria cell concentrations exceed 70,000 cells/mL. Advisories are not based on toxin evaluation but occur at cyanobacteria cell count densities when toxin production may be likely. These are intended as a precautionary measure for short-term exposure to cyanotoxins. When an advisory is issued, resampling is performed weekly until the bloom subsides. Advisories are issued from May 15 through October 15.

An alert may also be issued for a waterbody to serve as a statement to be on the watch for a potential cyanobacteria bloom. Sometimes alerts become advisories, and sometimes the bloom will pass before an advisory is issued. Alerts remain active for a week. Resampling only occurs if further bloom reports are submitted. Alerts are issued year-round as needed. An alert may be issued based upon a photo before NHDES can analyze a sample; if the cyanobacteria density is approaching 70,000 cell/mL but has not exceeded; or if the bloom has been reported to have passed by the time sample analysis is performed but may reoccur.

Beach Program Coordinator
Cyanobacteria Harmful Algal Bloom Program Manager