The Brazilian semiarid region present high rainfall variability and long dry periods. Thus, the main springs and streams are generally intermittent, and both native vegetation and human activities have a strong influence on hydrological processes and the water yield in the watershed. The aim of this study was to investigate the impacts of reforestation of the arboreal Caatinga on the availability of water in a representative basin of the Northeast semiarid with strong anthropic influence, considering a period of severe water scarcity from 2012 to 2015, using the SWAT model as a management tool. The SWAT model successfully simulated the flow hydrograph for the period from 2000 to 2015, with Nash-Sutcliffe (NS) efficiency coefficient of 0.77 and 0.55 in the calibration and validation. The simulated reforestation scenarios showed a 6 to 20% increase in recharge and soil water storage of 9 to 28%. Simulations of different scenarios of the Caatinga re-composition in agricultural areas highlight the strong impact of arboreal vegetation on hydrological processes, in particular on soil water infiltration and soil moisture increase.