Three major developments in the delivery of digital elevation models (DEMs) to the general public include the USGS national elevation dataset (NED), worldwide Shuttle Radar Topography Mission (SRTM) DEM for land area between latitudes 60°N and 60°S, and light detection and ranging (LIDAR) DEM for the state of North Carolina. These DEMs were created using different acquisition methods and technologies, and they can differ in how they represent the topography of the same area. This paper assesses the differences in these DEMs and illustrates how these differences can produce different analytical outcomes when used to study local problems. The Randleman Reservoir project in Guilford and Randolph counties, North Carolina, is used as a case study for comparing the DEMs. We found that a) the USGS, SRTM, and LIDAR DEMs differed, b) modeled reservoir extents and volumetric capacities differed substantially, with the USGS DEMs producing the smallest capacity and extent measurements and the LIDAR DEM producing the largest, and c) there was noncontiguous “ponding” on the reservoir extents derived from the USGS or SRTM DEM, but almost no “ponding” on the reservoir extents derived from the LIDAR DEM.