The sediments that transported in different ways to dam reservoirs decrease water storage capacity and shortens the reservoir lifetime. This forces the manager of water resources to monitor changes in water floor topography, and determine the sediment amount and sedimentation rate. This is very important in order to maintain current operations, make correct planning for future needs, take necessary precautions to prevent having a shorter lifetime than the projected durations and prolong the dams' lifetime. Although there are several different methods for determining the amount and rate of sediments, the most commonly used one is the bathymetric survey. In this study, in order to determine sedimentation of dams, a bathymetric survey was conducted in a part of the Obruk Dam Lake located in the Corum province of Turkey with the most recent geodetic equipment. The obtained results from the bathymetric survey are considered as initial results for the upcoming measurements to monitor the changes in sediment amount and sedimentation rate in the selected part of the Obruk Dam. The results imply that; the bathymetric surveying method is a powerful tool to estimate reservoir sedimentation.