Swimming advisory reported in Sanbornton, cyanobacteria bloom spotted on Lee’s Pond

As thousands travel to the Lakes Region to enjoy recreation on and around its many waterbodies, it’s worth noting a fecal matter advisory was issued at Sanbornton Town Beach, and the state Department of Environmental Services received a report of cyanobacteria on Lee’s Pond in Moultonborough.

A fecal bacteria advisory was issued for Sanbornton Town Beach, located along the shores of Lake Winnisquam, on July 1. An advisory does not close the beach, but is meant to warn the public regarding potential risk. NHDES staff recommend not wading or swimming in the water.

NHDES staff received a report about the cyanobacteria bloom on Lee’s Pond after a citizen observed one on June 30. No advisory there has yet been issued.

To stay up-to-date on water quality all weekend, use the NHDES Healthy Swimming Mapper at des.nh.gov/water/healthy-swimming/healthy-swimming-mapper. 

Sanbornton Town Beach

NHDES staff were scheduled to resample the water on July 2 and 3. Those results were not available as of press time.

Typically, staff with the NHDES Beach Program conduct sampling for fecal bacteria on Sanbornton Town Beach once each month between Memorial Day and Labor Day. When elevated levels of bacteria are identified, an advisory is issued to protect the public from potential illness while swimming.

Once a fecal bacteria advisory is issued, beaches are resampled until bacteria levels diminish below the standard threshold. NHDES staff have been sampling Sanbornton Town Beach since 2003, other than the period between 2019 and 2021, when sampling did not occur.

Water samples are collected at stations along the beach during routine inspections — there are two stations at Sanbornton Town Beach — and analyzed for the presence of E. coli, a fecal bacteria indicator for freshwater environments, according to NHDES staff. Results are available within 24 hours of collection.

New Hampshire beaches are considered “very good,” “good,” “fair” or “poor,” based on the percentage of samples collected which are clean. A clean sample is defined by a bacteria result lower than 88 parts per 100 mL, the state benchmark.

If two sample results from one beach are above the state standard, or if any one sample is above 158 parts per 100 mL, an advisory is issued. When a beach is under an advisory, signs are to be posted at all entrances. The advisory does not close the beach, and will be removed when sampling results show levels below state standards.

In 2024, six samples were collected from Sanbornton Town Beach, which was cleaner than average. In fact, 100% of samples taken there were clean last year, and the beach was categorized as “very good.” The beach was among 33 statewide which were listed as “very good,” while two were considered “good,” 14 were “fair” and 13 were “poor.”

Throughout the history of the sampling program, dating back to 2003, almost all samples collected at Sanbornton Town Beach were clean — less than 5% of 130 samples were not. Just six samples were not considered clean, and NHDES staff issued advisories four times, with an average duration of three days.

Potential sources of fecal bacteria contamination may include large numbers of swimmers, frequent wildlife visitors, failing septic systems nearby, storm drains or farm runoff. It’s recommended to avoid swimming following heavy rain and to refrain from feeding geese or gulls.

Lee’s Pond

According to the cyanobacteria bloom report received by NHDES for Lee’s Pond, an observer spotted the potential bloom near the shoreline on June 30. The observer described surface scum, mostly scattered thin ribbons of material in their report.

NHDES staff did not issue any cyanobacteria warnings or watches, but initial sampling showed a density of 234,600 cells per mL.

"These advisories are pretty localized to a specific area," Winnisqaum Watershed Network Executive Director Sara Steiner said Thursday morning. "Other areas of the lake should be safe to swim in."

Steiner said the advisory will last through the weekend, and resampling will occur on Monday, July 7.

"In the meantime, people should use their own best judgement," she said. "Stormwater runoff is usually one of our main sources of fecal pollution."

A cyanobacteria warning issued on Lake Kanasatka on June 10 was removed June 26. The only active cyanobacteria warning across New Hampshire is for Swains Lake in Barrington.

Water quality aside, it’s going to be hot this weekend. 

Sunday is expected to reach 93 degrees at the high point with essentially no shot of rain; it’s going to be clear and humid, and will only drop down to 69 degrees. Monday is also expected to be a scorcher, reaching highs of some 92 degrees with a low of 71 degrees, though there’s a moderate chance of rainfall. It’s expected to be clear, warm and humid.