This study investigates numerically the effects of the water intake operation of Castanh & atilde;o reservoir, Cear & aacute;, Brazil. First, transient hydraulic modelling was carried out using ALLIEVI. The results indicated that, even for the fastest closing conditions of the water intake valve, the impact of hydraulic transients was negligible. Next, computational fluid dynamics (CFD) simulations were performed using FLUENT to investigate the induced flow patterns approaching the water intake. With the turbulence values obtained, an empirical model as a function of the turbulent kinetic energy was applied to assess the thresholds for sediment resuspension. The results showed that the converging flow towards the water intake generated enough turbulence at the bottom of the reservoir to resuspend the sediment. However, the longitudinal extent of resuspension was limited to the areas relatively close to the intake. Finally, CFD simulations were carried out under well-mixed and thermally/chemically stratified conditions and for different withdrawal rates. For low rates, most of the flow was withdrawn from the upper water layers. Contrastingly, for high flow rates, a significant flow was also withdrawn from the lower water layers. As a result, the values of water quality parameters at the outlet increased up to about 30% for stratified water conditions.