To judge the feasibility of a project for interventions in watercourses under analysis by environmental agencies, it is necessary to address the diff erent environmental, social and economic interests. The challenge for assessing the environmental impacts of these projects is to consider the various aspects of hydro-environmental sustainability taking into account the diversity and complexity of river systems. Thus, with the objective of providing support and guiding technical teams from environmental agencies in the environmental licensing process for watercourse intervention projects, this exploratory, descriptive and interpretive research presents, as a result the Methodology for Hydroenvironmental Sustainability Assessment for intervention projects in perennial rivers (MASRios). The proposed Methodology is a semi-quantitative approach to sustainability assessment, which considers the hydrographic basin as a unit of territorial analysis. For this, the Methodology is based on Hierarchical river classifi cation by Horton (1945) modifi ed by Strahler (1952), from the Hierarchical dynamics of stretches by Frissel et al. (1986) and, the Hydro-environmental Impact Indicators and Sub-indicators prepared by Carvalho (2018). Finally, it is noteworthy that this instrument is exclusively applicable for the comparative assessment of the hydro-environmental impacts between the pre and post implementation stages of dams, dredging, rectifi cation and requalifi cation projects in 1st and 2nd order rivers with perennial regime, based on the application of data and information on the spatial observation scale from 1:1,000 to 1:10-1. .