In the thesis we firstly introduce dikes, their form, structure and the way of functioning. Theoretical bases of seepage and modes of failure, which can be caused by such a process, are explained. Further, optical fiber cables and the principle of their functioning in the monitoring of seepage are introduced. The method is based on thermal processes in a dike, because water affects its temperature conditions. By measuring the temperature using optical fiber cables the location and the rate of seepage can be
accurately determined. Although the method is relatively new, it has already come into practical use, and one of the applications is present at the dike of the hydroelectric power plant Brežice. We made a study of permeability of the dike and analysed three different cases. In the first case we presupposed that the dike is homogeneous, in the second one we treated the real dike, and in the third one we presupposed that the sealing membrane is damaged, which we modelled by increasing its permeability. The results showed the phreatic surface which enabled us to evaluate the form suitability of the dike and the position of optical fiber cables.