Sturbridge Great Ponds 2018 Report Card 
As usual, another summer season has ended all too suddenly, leaving memories of hot and humid weather, strong rainstorms, and hopefully, plenty of good times for the shoreline residents of Sturbridge’s Great Ponds (Big Alum, Cedar Lake, Leadmine Pond, Long Pond (part of East Brimfield Reservoir) South Pond, and Walker Pond). The docks are in, the boats out of the water, and the water surface is dotted with fallen leaves. As is our custom, the Sturbridge Lakes Advisory Committee (or SLAC) is reporting on the Ponds’ overall health, based on the annual summer water quality testing. Sampling was conducted on July 27th and 29th under the direction of monitoring teams led by Chris Mazieka, a long-term resident of South Pond. This year’s sampling represents the 17th consecutive year of data collection under leadership of SLAC and the Sturbridge Conservation Commission (SCC).
The summer water quality testing is sponsored by the Town, conducted by SLAC, aided by numerous dedicated volunteers and boat captains, with the cooperation of the SCC. Volunteer samplers collect water samples (both shallow and deep) and make field observations with regard to water clarity, temperature, and dissolved oxygen. Water samples are sent off for certified laboratory analysis of a variety of chemical parameters that provide insight into the current condition of the pond. We often liken lake testing to your annual physical – a time to check your overall health and look for any trends that may need further investigation. This year some of the “lake patients” showed a few signs of stress that may bear keeping an eye on in future years.
An important step is the lakes’ assessment is measurements of two essential nutrients, nitrogen and phosphorus, both very important in determining whether a lake experiences algal blooms during the summer. This is why it is important to limit the amount of these nutrients entering a pond from its watershed by using low or no-phosphorus fertilizer, leaving a vegetated buffer strip between your lawn and the lake, and not using local storm drains to dispose of oil or other fluids.
This year, phosphorus was a bit elevated in many of the ponds as compared to long term averages. It is suspected that this was due to greater than normal summer runoff arising from several powerful rainfall events preceding the sampling. Highest phosphorus levels were found in Cedar Lake (greater than 35 parts per billion where 25 ppb are considered excessive). Sure enough, later that summer, Cedar Lake endured problematic blue-green algal blooms, leading to prolonged closure of the public swimming beach. Similarly, Big Alum was slightly elevated (17 ppb) and also briefly experienced some noticeable accumulations of organic material along the shoreline in September.
Another important field indicator the survey measures is water clarity. Water clarity is assessed by lowering a white and black disk to a depth in the water until it just disappears – the deeper the depth of disappearance, the clearer the water. Clarity was in the good to average range in most lakes. Leadmine Pond had the best clarity with a visibility depth of 20+ feet, while only 3.7 feet was enough to lose sight of the disk in Cedar Lake. Consistent with the trends discussed above, Leadmine Pond has the smallest watershed of all local Great Ponds and had the lowest nutrient concentrations this year.
Even though some of the Great Ponds had less than perfect summers, the good news is that, with the exception of Cedar Lake, the current water quality of the rest fully supported all active recreational water uses. Climatic variation can lead to minor changes to lake water quality from year-to-year. This natural variation needs to be considered when trying to interpret whether lake health is trending up or down.
If you want more information about the results, feel free to contact SLAC. We also invite interested Town residents to participate in the annual sampling (we will train you) which is generally held in late July or August by contacting SLAC. The annual monitoring, along with good environmental stewardship of upstream watersheds and shoreline residences, provides a long-term defense for protection of these important natural resources that provide such an integral enhancement to the Sturbridge community.
David Mitchell