Water depths were measured during November 2015 and bathymetric elevations were computed for the lower Sixmile Creek reservoir in Ithaca, Tompkins County, N.Y. These data include ADCP-measured transect data and manually-measured point data collected by the U.S. Geological Survey, Ithaca, N.Y., during November 16-20, 2015. These data were used by the GIS Program, City of Ithaca, N.Y., to create a bathymetric surface (TIN) of the reservoir. Data collected in 1938 were used to create a second TIN and a contour line shapefile. This dataset includes the ADCP-measured transect data and manually-measured point data collected by the U.S. Geological Survey, Ithaca, N.Y., during November 16-20, 2015, and the two bathymetric-surface TINS (for 1938 and 2015) and a 1938 contour line shapefile that were created by the GIS program, City of Ithaca, N.Y.