Abstract: In this paper we evaluate the hydrological impact produced on the river mean daily discharge (water) of Buzău River by Siriu Dam. The study data was the daily mean discharge registered from the 1^st of January 1955 to the 31^st of December 2010, at the Nehoiu hydrometric station on the Buzău River. The flow of this river is controlled in its upper reach by Siriu Dam, from 1984. The main method used for the evaluation of the hydrologic alteration at temporal scale was based on the tests provided by the Indicators of Hydrologic Alteration (IHA) software. The statistical analysis proved that the built of Siriu Dam had a moderate influence on the mean daily discharge regime of Buzău River at large time intervals, significant changes appearing at small time scales.