Brazil gets two-thirds of its energy from hydropower and has numerous large hydropower storage reservoirs that are fed by perennial rivers. Although it is usually understood that the construction and operation of hydropower systems reduce the river flow downstream due to the increase in evaporation, a recent study suggests that in humid conditions, as found in parts of Brazil, hydropower storage reservoirs actually contribute to increasing the flow of the river upstream of the reservoir. “It is widely accepted that river flow impacts reservoir levels. This is true...