Impacts of climate change on the Tagus Segura interbasin water transfer

According to different previous studies, water resources availability in semi-arid regions will be highly affected by climate change very likely. The Segura river basin, located in the southeast of Spain, is one of the most water-stressed basins in Mediterranean Europe (EEA 2009). One of the major source of water in this basin is the Tagus-Segura interbasin water transfer (TSWT), whereby about 400 Mm3 /year of water is transported from the headwaters of the Tagus river basin, in central Spain, to the southeast along a 300 km channel. TSWT has enabled the socio-economic development of the south-east of Spain and supports important economic activities in this area (urban-industrial water consumption and irrigated fruits and vegetables production), although it involves political decisions at a national level, and has been the focus of territorial conflicts (Melgarejo-Moreno et al. 2019). Recent studies (Lobanova et al. 2017; Pellicer-Martínez and Martínez-Paz 2018) reveal that climate change would imply reductions in the flows that could be transferred to the Segura basin. In this study, we have gone one step further, improving the modelization of the basin using the Soil & Water Assessment Tool (SWAT) model and SWAT2lake tool (Molina-Navarro et al. 2018). This tool let the modeller delineate the entire watershed flowing into a reservoir including not only the major streams but also those areas inbetween river's subbasins that flow directly into the reservoir. Besides, the TSWT operating rules were simulated taking into account the effect of projected temperatures on the reservoirs evaporation. The overall objective of this study was to evaluate the hypothetical effects that both components of climate change -flows and evaporation from reservoirs- may have on the water transferred to the Segura river basin..