The trend of the flow in different time periods is the main indicator of a hydrological regime of water level fluctuations in analysing of the watercourse. On the basis of the daily flow data for a given watercourse we can figure out, how the hydrological condition changes through time, and how it Will be reflected in the near future. In this thesis I made an overall analysis of the flow for several Slovenian rivers, and compared the result with previous values of the same flow of the watercourses. I tried to figure out the differences between different time periods in the same stream as well as to identify the impact of potential changes in the hydrological characteristics and factors for the formation of the flow regime. I used the time trend, Pearson correlation coefficient and Mann-Kendall test for trend. I also analyzed river flows with models AM annual maximum and POT peak-overthreshold. The results show a decrease in flow of the Slovenian rivers, on the other hand, increasing the already high flows. I analyzed the global climate impacts and their influence on the properties of flow.