Climate change effects in a Mediterranean island and streamflow changes for a small area using EURO-CORDEX simulations combined with the SWAT model

Climate change effects on the hydrologic cycle are a main concern for the evaluation of water management strategies. Climate models project important precipitation changes for the future, considering greenhouse emission scenarios. In this study, the EURO-CORDEX (European COordinated Regional Downscaling Experiment) climate models were first evaluated in a Mediterranean island (Sardinia), against observed precipitation for a historical reference period (1976-2005). A weighted Multi-Model Ensemble (ENS) was built, weighting the individual models based on their ability to reproduce observed rainfall. Future projections (2071-2100) were carried out, following the RCP-8.5 emissions scenario, to evaluate future changes in precipitations. ENS was then used as climate forcing for the SWAT model (Soil and Water Assessment Tool), with the aim to assess the consequences of such projected changes on streamflow and runoff of two small catchments located in the South-West Sardinia. Results showed that a decrease of mean rainfall values, up to -25 % at yearly scale, is expected for the future, along with an increase of extreme precipitation events. Particularly, in the eastern and southern areas, extreme events are projected to increase by 30%. Such changes reflect on the hydrologic cycle with a decrease of mean streamflow (-18% to -25%) and runoff (-12% to -18%), except in spring, when runoff is projected to increase by 20-30%. These results stress that Mediterranean is a hotspot for the climate change and the use of model tools can provide useful information to adopt water and land management strategies to deal with such changes.