The paper focuses on the development of the hydraulic–hydrological model used to simulate water resources management scenarios in the Zambezi River basin. The main challenges of the implementation of the model are the scarcity of continuous reliable discharge data and the significant influence of large floodplains. The Soil and Water Assessment Tool, a semidistributed physically based continuous time model, was chosen as simulation tool. Given the complexity and the size of the basin under study, an automated calibration procedure was applied to optimize the relative error and the volume ratio at multiple stations. Using data derived from satellite observations, the model is first stabilized during two years, then calibrated over six years and finally validated over three years. The study evidences the importance of evaluating the model at different points of the basin and the complementarities between performance indicators.