The Conservation Commission voted unanimously at its September 5 meeting to approve a 6-foot drawdown for Bare Hill Pond this winter, continuing a practice that has been followed nearly every year since 2002.
Bruce Leicher, chair of the Bare Hill Pond Watershed Management Committee, and Wendy Gendron of Aquatic Restoration Consulting LLC of Ashburnham gave the commission a brief report on the pond’s condition, based on tests Gendron did in June and July.
One key to the pond’s health, Leicher said, has been keeping phosphorus levels low, thus preventing the growth of algae. The drawdown flushes out the phosphorus that washes into the pond from the surrounding area each year. Phosphorus levels are less than half of what they were before the drawdown program began, Leicher said.
Leicher noted that several other area lakes have been closed to swimmers because of algal blooms this year, and he credited a low phosphorus level with preventing that problem in Bare Hill Pond. Gendron differed slightly, saying that high phosphorus levels do correlate with algal blooms, but have not been shown to cause them.
Conservation Commission Chair Don Ritchie asked whether the phosphorous pumped out of Bare Hill Pond might create a problem in the wetlands downstream, where the pumped water is released. But Gendron said the rich plant growth in the wetlands quickly takes up the phosphorous. “It’s been a great year for plants,” she said.
Gendron acknowledged that plant growth in the pond itself was somewhat higher than last year, which could be a nuisance to swimmers and boaters. But the two species that showed the most noticeable increase were tape grass and pondweed, both natives that provide beneficial habitat. In a letter accompanying her report, she wrote, “These plants have likely kept invasive species from recolonizing these areas.”
In an earlier telephone conversation, the Press asked Leicher about reports of blue-green algae in Lake Boon, which forced Stow to close its town beach and which was suspected of causing the deaths of two dogs, according to accounts on the social media site Nextdoor. Leicher explained that so-called blue-green algae is not actually algae at all. It is a bacteria known as cyanobacteria, and it thrives in warm water that is high in nutrients such as phosphorus. So smaller ponds and wetlands in town, where phosphorus levels might be higher, could pose a danger to dogs, he said. But Bare Hill Pond has kept clear of the problem.
