Estimations of reservoir bathymetry and storage are of great significance due to their substantial impacts on hydrological processes and water resource management. However, existing approaches for reservoir bathymetry construction often rely on field measurements, which restricts their application at regional and global scales. This study proposes a novel Approach for Determining the BAthymetry and water storage of channel-type Reservoirs, named as ADBAR, for which only open-access digital elevation model (DEM) and satellite images are required. The main idea of ADBAR lies on the geomorphological similarity and topographic continuity of the reservoir bathymetry in both along-channel and cross-channel profiles. The spatial reconstruction of reservoir bathymetry is enabled by utilizing the topography information in longitudinal (upper and lower reaches) and lateral directions. Three modes (U-shape, V-shape, and Flat-shape) are designed for different types of reservoirs by referring to the surrounding river morphology.