1 INTRODUCTION Our main interest is an impact of the anthropogenic changes on the evolution of hydrologic regime. The presented studies focus on Jeziorsko dam built in the Warta river, Poland, and intensive water manage- ment in the reservoir. These actions changed the ve- locity patterns in the Warta river and induced several sediment transport related processes. The trans- ported material was deposited in inlet part of the res- ervoir and taken from the reach downstream of the dam. In the presented study we focus on the upper part of the reservoir. The sediment accumulation in the river channel induced one more process affecting hydrologic regime. Due to the increase of floodplain inundation frequency, the luxuriant vegetation start to grow there. These two processes, sediment accu- mulation and vegetation growth, cause additional in- crease of floodplain inundation. The processes in- duced by the dam built and performance seems to be self-driven cycle causing irreversible alterations of hydrologic regime. The problems studied here are intensively inves- tigated during last decades. The main reason for such interest is their importance for the water man- agement, regional economy and people safety. Ex- ample linking hydrological regime and riparian vegetation dynamics was given by Keeland et al. (1997). The Authors linked the annual average depth in the river floodplains and tree diameter. Other ex- ample is paper written by Surtevant (1998) who ana- lyzed the riparian wetland vegetation dynamics re- lated to the flow changes and sediment accumulation. The relations between hydrologic re- gime and riparian vegetation were studied by Strom- berg (2001). Similar research done by Nilsson and Svedmark (2002) resulted in formulation of basic principles and consequences of water regime changes. The changes of the hydrologic regime may be in- duced by many different factors, anthropogenic as well as natural. However, one of the most important anthropogenic impacts on the hydrologic regime is damming of the river as it is well shown in Petts and Gurnell (2005). The studies on the hydrologic changes and degradation of ecosystems located along the river reaches below the dams were pre- sented by several researches. The examples may be found in Maingi and Marsh (2002), Magilligan and Nislow (2005), Marston et al. (2005) and many oth- ers. The dam impact on the upstream condition is also intensively investigated. Interesting examples were given by Mumba and Thompson (2005) and Pinter and Heine (2005). In the first paper the changes in the floodplains located along the Kafue river (Zambia) reach between two dams, Itezhi-tezhi (upstream) and Kafue Gorge (downstream) are ana- lyzed. The Authors proved that dams totally changed the hydrological and ecological conditions in the re- gion due to the almost permanent inundation. Such conditions were imposed by parallel influences of releases from upper dam and high water levels in the lower reservoir. In the second paper, the flood mag- Man-induced morphological processes in Warta river (Poland), and their impact on the evolution of hydrological conditions T. Dysarz, J. Wicher-Dysarz & B. Przedwojski Department of Hydraulic Engineering, Agricultural University of Poznan, Poland ABSTRACT: In the paper the overview of morphological processes occurring in the selected Warta river reach is given. The processes were induced by the performance of the Jeziorsko dam, which was built in 1986. The main purpose of the presented research is the assessment of these processes impact on the hydro- logic conditions in the river system. The historical data and hydrodynamic simulation model are used for the assessment of the hydrologic changes. The data consists of field measurements of the river morphology and hydrologic data from the selected river gages. The hydrodynamic model was used to reconstruct the flow conditions in particular states of the river system evolution. The statistical analysis of the obtained results en- abled the assessment of the hydrologic characteristics transformation in the selected Warta river reach. The results are presented as relative and cumulative curves related to the estimated stages of the river system. The presented analyses shows significant changes of the hydrologic regime in the considered area.