Summary:

The development of vegetation in lotic waters, including macrophytes, is determined by diverse factors, including bottom substrate, flow velocity, and the width and depth of a channel, which are hydromorphological parameters. Macrophytes are higher plants of terrestrial origin which have undergone numerous adaptations enabling them to live in water (Stańczykowska, 1975). The aim of the study was to assess the effect of selected hydromorphological parameters of a watercourse on the species composition of macrophytes. The subject of the study was the Chechło River, a left tributary of the Vistula. The study was carried out in two adjacent segments of the watercourse, according to guidelines in the Macrophyte Index for Rivers (MMOR) and elements of the River Habitat Survey (RHS). The study revealed similar hydromorphological conditions in the two segments of the river, and the variation in the species composition of macrophytes in the two segments seems to be determined by other factors which were not the subject of the study. Among these, significant factors might include regulation works or the high water levels in the Chechło resulting from the construction of an impoundment. The plants identified in the two segments of the watercourse are species occurring commonly in Poland, preferring eutrophic waters and having a wide ecological tolerance.