My task was to prepare a mathematical model of the Vah's riverbed between the hydroelectricity power plants Lipovec and Žilina on the basis of direct measurement of transformation of the flow waves from the year 2012 and of the geodetical measurements, which task was to measure out the geometry of the Vah's riverbed. It was necessary to synchronize the measured data with the flow regime from the hydroelectricity power plant Lipovec. As a result, from these datas it was possible to calibrate and verificate the model, then find out the surface regime. The initation of the unsteady flow regime on this helped me to determine the flow period time of the energeticaly unused part of the Váh cascade. The model is also usable for determination of the impact from the hydropower plant Lipovec on the hydropower plant Žilina.