Аннотация:Hydrodynamic conditions in a tidal estuary are very complex and depend on a wide range of factors. This was also demonstrated in the previous studies for the estuary of the Onega River, which were primarily based on the analysis of field measurements. In this paper, the results of numerical modelling performed using 1D and 2DH/3D «shallow water» approaches are presented, for summer and winter hydrological conditions in the Onega River estuary. The models were built and calibrated using extensive field data, which allowed assessing the opportunities to model the temporal and spatial variability of water levels, discharges, and velocities in a dynamic environment of a tidal estuary.