Check out the NHDES Healthy Swimming Mapper for more details and daily updates. | | |
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Active Cyanobacteria Warnings (Advisories):
New Warnings
- Whittemore Lake, Bennington, issued 28 August 2023
- Sondogardy Pond, Northfield, issued 29 August 2023
Continuing Warnings
- Arlington Mill Reservoir, Salem, issued 28 July 2023
- Tucker Pond, Salisbury, issued 31 July 2023
- Showell Pond, Sandown, issued 1 August 2023
- Long Pond, Pelham, issued 21 August 2023
- Little Island Pond, Pelham, issued 22 August 2023
- Jericho Lake, Berlin, issued 23 August 2023
- Duncan Lake, Ossipee, issued 24 August 2023
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Active Cyanobacteria Alerts:
- Pearly Pond, Rindge, issued 9 August 2023
- Spofford Lake, Chesterfield, issued 16 August 2023
- Melendy Pond, Brookline, issued 23 August 2023
- Lake Wentworth, Wolfeboro, issued 24 August 2023
- Lake Winnipesaukee - Alton Bay & Wolfeboro Bay & The Broads, Alton/Wolfeboro, issued 24 August 2023
- Great East Lake, Acton/Wakefield, issued 25 August 2023
- Lake Francis, Pittsburg, issued 25 August 2023
- Lake Horace (Weare Reservoir), Weare, issued 25 August 2023
- Lake Monomonac, Rindge, issued 25 August 2023
- Northwood Lake, Northwood, issued 25 August 2023
- Contoocook Lake, Jaffrey/Rindge. issued 30 August 2023
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Cyanobacteria Warnings (Advisories) Removed:
- Baboosic Lake, Amherst, issued 11 August, closed 25 August 2023
- Sunrise Lake, Middleton, issued 17 August, closed 29 August 2023
- Pine Island Pond, Manchester, issued 22 August, closed 29 August 2023
- Marsh Pond, New Durham/Alton, issued 18 August, closed 31 August 2023
- Belleau Lake, Wakefield, issued 24 August, closed 31 August 2023
- Province Lake, Effingham/Wakefield, issued 6 July, closed 31 August 2023
- Lake Kanasatka, Moultonborough, issued 7 August, closed 31 August 2023
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If you notice anything resembling cyanobacteria, please refrain from wading, swimming, or drinking the water. Keep all pets out of the water and report it to NHDES immediately. Remember, when in doubt, stay out. | |
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What is a Warning (Advisory)?
Advisories are lake-wide warnings issued when cyanobacteria cell counts exceed the recreational health threshold of 70,000 cells/mL. Surface blooms can rapidly change and accumulate in various locations around a waterbody. Please continue to monitor shorelines for changing conditions. NHDES advises lake users to avoid contact with the water in areas experiencing blooms. Pets and livestock should also be kept out of the water.
When an advisory is issued, resampling is performed weekly until the bloom subsides. Advisories are issued from May 15 through October 15. Advisories are not based on toxin evaluation but occur at cyanobacteria cell count densities when toxin production may be likely and are intended as a precautionary measure for short term exposure to cyanotoxins.
Blooms are dynamic. Always perform a self-risk assessment of the water, looking for discoloration or unusual growth prior to recreating. If you see cyanobacteria develop after an advisory has been closed, please report it.
What is an Alert?
Alerts are issued 1) based on a photo before NHDES can analyze a sample; 2) when the cyanobacteria density is approaching the recreational health threshold but does not yet exceed it; or 3) if a bloom was reported but may have passed by the time a sample was reviewed but could reoccur. Alerts are intended to serve as statements to be on the watch for a potential cyanobacteria bloom. Waterbody users should avoid contact with bloom material and keep pets and livestock out of the water. Sometimes alerts become advisories, and sometimes they pass. Alerts remain active for a week. Resampling only occurs if further bloom reports are submitted. Alerts are issued year-round as needed.
Cyanobacteria Basics:
Cyanobacteria are natural components of water bodies worldwide, though blooms and surface scums may form when excess nutrients are available to the water. Some cyanobacteria produce toxins that are stored in the cells and released into the water when the cells die. Toxins can cause both acute and chronic health effects that vary in severity. Acute health effects include irritation of the skin and mucous membranes, tingling, numbness, nausea, vomiting, seizures, and diarrhea. Chronic effects may include liver and central nervous system damage. Be cautious of lake water that has a surface scum, changes colors, or appears to have green streaks or blue-green flecks aggregating along the shore.
If a person or animal is sick from a potential cyanobacteria exposure, please seek medical attention. Inform your physician or veterinarian that you or your pet may have been exposed to toxic cyanobacteria via recreation. Please also fill out our Illness Report Form, and see the CDC guidance for Health Care Providers and Veterinarians.
Questions?
For more information, see the NHDES Harmful Algal Bloom Webpage and our Frequently Asked Questions. Sign up for waterbody- specific emails to receive more details for that specific waterbody (advisory or alert issuance, resampling results and advisory removal).
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