This paper analyses the cross-sectoral integration of the water-energy nexus in Brazil. Recent droughts resulted in unprecedented water scarcity. This caused water shortages for population and agriculture, as well as for electricity production (hydropower being the main source of electricity production). As a result, the system became more vulnerable to blackouts. To alleviate the problem, fossil fuels were used as a back up. Droughts, floods and other water-related problems will not dissipate as time goes by in Brazil. The dependency on one single predominant source (hydropower) makes Brazil’s electricity supply vulnerable. This study shows through data analysis, flow diagrams and metrics the interrelation between water and energy. Based on historical data, the analysis shows the importance of the water demand for hydropower, cooling for thermal plants, and the extraction and production of biofuels, as well as of the energy demand of water services (water supply, wastewater treatment).