Assessment and Condition of a Small River in Urbanized Areas (Example of the Kurdyum River of the “Saratov City” Municipal Entity)

The results of study of the ecological status of the Kurdyum River within the “Saratov city” municipal entity are presented. The hydrochemical regime, hydrophilic flora, and vegetation of the watercourse were studied in the 2022–2023 field seasons. The ecological status of the river was assessed by the structural parameters of macrophytes. The species composition of aquatic plants in the Kurdyum River was represented by 41 macrophyte species belonging to 32 genera, 23 families, and three divisions (Charophyta, Polypodiophyta, and Magnoliophyta). The families Potamogetonaceae, Asteraceae, Poaceae, Typhaceae, and Ranunculaceae predominated by the number of species. The genus Potamogeton contained the greatest number of species (four), while other genera were represented by one–two species. Hydrophytes were a numerous ecological group, accounting for 51% of the total number of species. New locations of species that are rare for Saratov oblast (Myriophyllum verticillatum and Zannichellia palustris) were revealed. The vegetation cover of the Kurdyum River is characterized by the greatest phytocenotic diversity of true aquatic vegetation. The impoverishment of the phytocenotic composition of helophytic and hygrophytic vegetation is explained by the lack of favorable conditions for the development of their phytocenoses (the watercourse has abrasion banks along a significant length) or trampling and eating by grazing animals. The river studied is characterized by species diversity in comparison with urban watercourses studied previously. Index comparison has revealed an inverse relationship between species diversity and the level of anthropogenic load. Cluster analysis has revealed that the structure of flora and vegetation from the source to the mouth of the river is not homogeneous and is formed under the influence of a combination of hydrological, chemical, and anthropogenic factors. The results of our chemical analysis of the water showed that the maximum permissible concentrations of Fe, Zn, Cu, surfactants, NO2, and NH3 were exceeded throughout the river. However, the environmental indicators assessed based on the structural parameters of macrophytes allow us to consider the ecological status of the watercourse satisfactory. Thus, the Kurdyum River is moderately polluted with a high trophic status.