The fragility of the environment can be seen as a research proposal whose basic principle is to define the different levels of fragility of the natural environments and of the environments altered by the anthropic activities. The objective of this study was to evaluate the environmental fragility levels in the hydrographic basin of the reservoir of the Caçu Hydroelectric Power Plant (HPP) in two distinct periods: before the formation of the reservoir (2009) and after the formation of the reservoir (2014). The methodology used followed the proposal of Ross (1994). The evaluated parameters were: soils, declivity; erosivity and land use. The results show that the basin analyzed had the predominance of the low fragility class, which occupied 74.88% of the area of the basin in 2009 and 77.52% in 2014, the class of medium fragility, in 2009, occupied 20.79 % of area, and in 2014 it came to occupy 21.12%. High fragility decreased from 4.34% in 2009 to 1.36% in 2014, due to changes in basin soil use. It should be noted that approximately 25% of the area of the basin is classified as medium to high fragility, demonstrating the need for special care and use of conservation practices in relation to land use.
