Save Minnewawa Association was formed in 1977 and they purchased their first aquatic vegetation harvester in 1982. Since the harvester has been in use, not only have the amount of weeds decreased, but the water clarity has significantly increased.

A big reason for this is because there are fewer weeds dying in the lake and decomposing in the bottom of the lake. Also, the weeds contain a huge amount of phosphorous which is being removed along with the weeds. The more phosphorous in a lake, the more algae growth, therefore the lower the water clarity.

The board has heard the suggestion of controlling the weeds by using chemicals instead of the weed harvester. The cost of the chemicals is very prohibitive though. It was $250,000 dollars and the lake had to be treated twice a year for the first 5 years; a price tag of a half million dollars. Compared to approximately $25,000 a year it takes to run the weed harvester.

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Georgica Pond has been invaded by toxic cyanobacteria, or blue-green algae, in recent years, which can cause serious health problems.  For the second consecutive year, the foundation has leased an aquatic weed harvester to remove plant material, or macroalgae, from the pond, which releases nitrogen and phosphorous as it decays and is believed to promote cyanobacteria.

The mechanical harvester 32,700 pounds of this material represent 6% of the pond’s nitrogen load and 12% of its phosphorous load; down from 2016 when 55,740 pounds, representing 13% of the nitrogen load and 23% of the phosphorous load, were harvested.  Officials say part of the reason for the decrease in 2017 was due to the large quantity of macroalgae harvester the previous year.

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