In recent years, energy transition process has been directing the world's electrical systems in a search for the insertion of clean and renewable energy sources. In Brazil, hydroelectric generation plays a fundamental role, with 68% of energy supplied by hydraulic sources in 2019. However, despite hydroelectric generation being considered a renewable energy and with low emission of polluting gases, the construction of hydroelectric plants can cause significant consequences in the dynamics of territorial management, especially when located in regions of high socio-environmental complexity. Considering the importance of hydroelectric projects, it is essential to understand the impacts arising from their implementation in the Brazilian territory. This article aims to analyze the socioeconomic impacts arising from the construction of hydroelectric plants in municipalities affected by reservoirs. To this end, it is proposed to analyze the case study of the Estreito hydroelectric plant, located in Maranhão, through the application of the Synthetic Control impact assessment method. The results demonstrate that the positive externalities of the plant's implementation, when they exist, are short to medium term, except for the income dimension. On the other hand, the deterioration of the other dimensions analyzed indicates a possible reduction in the quality of life of the local population.