Most lakes in the Lower Hudson Valley must contend with seasonal algal blooms. Kirk Lake is no exception, so KLWA has been collecting water quality data and will also gather New York City's water testing data to develop a watershed management plan to attack this problem.
Occasional blue-green algal blooms are of particular concern. If you see a significant greenish mat-like substance on the water's surface, it's probably a good idea to avoid swimming. Young children -- who tend to ingest more water than adults, should especially avoid swimming during these times.
For more information, see the NYS Health Department PDF below.