Phytoplankton community structure and biovolume were measured in Falling Creek Reservoir, Vinton, VA, USA during four summers from 2016-2019. Falling Creek Reservoir is a drinking water supply reservoir owned and operated by the Western Virginia Water Authority. Phytoplankton depth samples were collected weekly at the deepest site in the reservoir from May-September each year and periodically (ranging from weekly to monthly) at other times of year. The depth of the samples was chosen to match the depth of the chlorophyll maximum, which was determined on each sampling day by a submersible fluorescence-based profiler. During the entire monitoring period, these depths ranged from 0.1-7 m, with a median of 3.8 m. The maximum depth of Falling Creek Reservoir is 9.3 m. Samples were collected in 250 mL amber high-density polyethylene bottles and immediately preserved by adding approximately 1% Lugol's iodine by volume to each sample. Sub-samples were filtered and preserved on permanent slides before counting using a compound light microscope. Phytoplankton greater than 5 um along the greatest axial linear dimension were identified to genus at 400x magnification.