The aim of this work was to evaluate the development of submerged vegetation, specifically canopy height, considering space and time dimensions, using hydro-acoustic techniques. Ten field surveys were carried out, from October2009 to December 2010, to acquire geo-referenced points of canopy height, vegetation occurrence frequency, and depth. Limnological measurements were also made to verify whether their variations could explain the spatial distribution of the macrophytes. The canopy data were analyzed by survey and depth. The data were imported to a Geographic Information System to be interpolated. The generated surfaces were used to build cartographic representations of vegetation growth or decay. Three dimension models ofthe canopies were also produced to represent the volumetric occupation of the submerged macrophytes. The results showed a significant infestation reduction from one year to the next. It was also observed that the highest canopies have a depth of 2 to 4 m. The mapping identified both growth and decay areas, distributed heterogeneously. No direct relation was detected between the limnological measurements and vegetation growth, since these presented no significant spatial-temporal variation. The volume occupied by the vegetation was estimated, and the trend shows that volume increase is preceded by an apparent canopy homogenization.
mapping; growth; volume; geographical information system
