This master's thesis deals with an experimental research of the intake flow conditions on cooling towers pumping system in the Nuclear Power Plant in Krško. Formation of the free surface vortex type 6 in the pump sump was not acceptable for the operation of the CT1 pump and the cooling system in general. Detailed flow conditions in the intake structure were needed. Field measurements as well as a design of the physical hydraulic model with a scale factor 16 were conducted in the laboratory. Pumping systems, intake structures and centrifugal pumps are described in the theoretical part of this paper. This section provides a theoretical background in describing the flow through conservation laws pumping systems, free surface flow, dimensional analysis, with an emphasis on free surface flow and measurement uncertainty. The chapter is followed by an overview of research dealing with the issues of intake structures. The empirical approach and recommendations of Standard ANSI/HI for pump intake design and for designing a physical hydraulic model are introduced. At the end of the theoretical part, measurement techniques and measuring procedures are included as well. The following experimental sections presents an example of the analysis of a CT pumping station, providing field measurements and model tests in the laboratory. The model tests were made for different operational conditions of pumps. Comparison between the model and the prototype showed a good agreement with the formation of identical free surface vortex type 6 in the same area of the sump. In order to prevent the formations of an unfavorable free surface vortex, the geometry of intake structures with the additional elements and obstacles were modified. The model test which included an installation of an extended intermediate wall provided favorable flow conditions in the acceptable criteria of Standard ANSI/HI.