EN
High iron concentrations have been found in the surface layers of the bottom sediment in the backwater of the reservoir. The elevated concentrations were observed over 1994-1996, followed by a decrease after 1997. Both the temporal and spatial changes in iron concentration in the sediment reflected the influence of main contamination sources on the reservoir i.e. the inflow of contaminants from the Ruda river and the impact of long-range transport of pollutants from Upper Silesian Industrial Region and Rybnik Coal Mining Region. The changes in iron concentration were also significantly affected by the flood in 1997.