Through the NH Department of Environmental Services Volunteer Lake Assessment Program (VLAP), Crescent Lake volunteers collect samples of the lake water for lab testing and perform other tests three or more times each summer. The crew collects water samples from different depths at the lake’s deep spot, as well as at the dam outlet and inlets (northeast and west).

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Samples are tested at the LSPA Lab at Colby-Sawyer College in New London for pH, phosphorus, chloride, conductivity, turbidity, color, and chlorophyll-a. DES staff members use these test results to prepare an annual report on Crescent Lake water quality and trends. We have more than 30 years of data. Lab fees are paid by the Unity and Acworth Conservation Commissions.

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In addition to lab work, several volunteers also check water transparency using a Secchi Disk. The black-and-white disk is lowered until it is no longer visible and the depth is recorded.

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Finally, at the deep spot we measure the water temperature every meter from top to bottom and have recently started measuring dissolved oxygen levels as well. Our concern is that the bottom layer of water is warming and if it becomes critical, available oxygen is reduced allowing the extraction of phosphorus from the sediment.