Propagation of droughts with Standardized Indexes associated with storage services under changes

During drought periods, reservoirs are intended to ensure water availability to meet specific demands within a river basin. However, the increasing frequency and duration of droughts that may be caused by climate change and rising population demands for water may prevent reservoirs from replenishing the necessary volumes for subsequent drought events, potentially prolonging their effects. This study aims to investigate how reservoirs can influence the time of propagation of droughts in the context of climate change, in Brazilian river basins located across different biomes. To achieve this, i) the time of propagation from meteorological to hydrological droughts was calculated using standardized indices for the period 1990 to 2024; additionally, ii) in each basin, drought events in a main reservoir was evaluated using the Standardized Reservoir Drought Index over the same period; and finally, iii) indicators representing the effects of climate change — such as the temporal evolution of evapotranspiration — and increased water demands driven by human activities — such as changes in land use and occupation in agricultural and urban areas— was also be assessed for the same period. This analysis seeks to discuss potential relationships among the time of propagation time to hydrological droughts, reservoir droughts, population demands, and climate change.