This research studies the effect of climate change on the hydrological behavior of two semi-arid basins. For this purpose the SWAT model was used, with the simulation of two future climate change scenarios, one moderate (RCP 4.5) and the other extreme (RCP 8.5).Three future periods were considered: close (2019-2040), medium (2041-2070), and distant (2071-2100). Also, several climatic projections of the EURO-CORDEX model were selected, to which different bias correction methods were applied before incorporation into the SWAT model. The statistical indices for the monthly flow simulations showed a very good fit in the calibration and validation phases in the Upper Mula stream (NS = 0.79 - 0.87; PBIAS = -4.00% - 0.70%; RSR = 0.44 - 0.46) and the ephemeral Algeciras stream (NS = 0.78 - 0.82; PBIAS = -8.10% - -8.20%; RSR = 0.41- 0.42). Subsequently, the impact of climate change in both basins was evaluated by comparing future flows with those of the historical period. In the RCP4.5 and RCP8.5 scenarios, by the end of the 2071-2100 period the flows of the Upper Mula stream and the ephemeral Algeciras stream will have decreased by between 45.16% and 59.35% and between 45.89% and 63.85%, respectively.