The semi-quantitative Kohler method for macrophytes mapping was used. The canals have been divided longitudinally into survey units based on homogeneity of plants and ecological conditions while the bound-aries have been measured using the GPS device GARMIN (WGS 84 system). Due to its width it was not possible to determine the homogeneous survey units across the full width of the Patinsk´ y canal, thus the left and right sides were examined separately. The plant mass estimate (PME) index of individual macrophyte species was determined in each survey unit applying a 5-grade scale (Kohler 1978; Kohler and Janauer 1995; Janauer 2003).