Climate change may have significant consequences on water resources availability and management at the basin scale. This is particularly true for areas already suffering from water stress, such as the Mediterranean area. This work focuses on studying these impacts in the Llobregat basin supplying Barcelona’s region. Several climate projections, adapted to the spatiotemporal resolution of the study, have been combined with a daily hydrological model to estimate future water availability. Depending on the scenario and the time period, different assessment indicators like reliability and resilience show a future decrease in water resources (up to 40%), with drought periods more frequent. An additional uncertainty analysis has also shown a high variability of results (annual water availability ranging from 147 hm3/year to 274 hm3/year), thus making accurate projections difficult. Finally, the study illustrates how climate change could be taken into account to provide adaptative measures for the future.