In Bolivia, hydroelectric projects are gaining relevance as a source of renewable energy, which is why there is little record of specific experiences on the implementation of hydroelectric projects in mountain areas that include an analysis of the environment within the framework of sustainability energetic. The present study takes a hydroelectric reservoir project established in a mountain ecosystem as a unit of analysis to demonstrate that a hierarchy of environmental impacts responds more precisely to the environmental dimension, according to its technical and ecosystem characteristics. The development of the work starts with the analysis of the information recorded in the Environmental Impact Assessment Study - EEIA and based on this information, a procedure is carried out to rank the environmental impacts with the use of matrix, qualitative and quantitative methods, in addition to the use of specialized software. Finally, it is concluded that there are no standard evaluations, and it is affirmed that the EIA of any hydro-energy project, whether established or not, in a mountain ecosystem, is a complex and unique problem. Therefore, a hierarchical ranking of environmental impacts in an initial and particular way to the project site area contributes in a real and effective way to an environmental sustainability of the intervened ecosystem, within the framework of Sustainable Energy Development.