Summary:

The aim of the following research was an assessment of the impact technical interference has over Smortawa riverbed`s hydromacrophytes communities. The measure of this impact based on the following four biological factors: the number of species, the degree of the bottom coverage, Shannon-Wiener index and Macrophyte River Index. Field study was performed in vegetation season of 2012 in three river sections presenting different degree of anthropogenic modification: natural, modified moderately in the result of ecoregulation and severly modified in the result of technical interference. In order to assess the impact of modification on the quality and quantity of hydromacrophytes communities Spearman`s ranks correlation analysis was performed.
Performed analyses indicated that the biodiversity of biological indexes in study sections in linked with the range of works conducted in the riverbed. Stronger connection with these factors showed elements of the watercourse system modified in a result of technical interference such as: river filing, shape of the riverbed, width of the bottom and the way of scarp`s strengthening and shading the watercourse.