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24 Pag., 5 Fig. The definitive version is available at: http://www.int-res.com/abstracts/cr/ ; We analysed the evolution of drought on the NW Iberian Peninsula from 1930 to 2006, and identified differences between the effects of precipitation variability and warming processes on drought severity and surface water resources. Two drought indices were used, one based on precipitation (the standardised precipitation index, SPI) and the other based on water balance, as reflected by the difference between precipitation and potential evapotranspiration, PET (the standardised precipitation evapotranspiration index, SPEI). The results show that precipitation has increased in the region, but a significant increase has also occurred in PET. No statistically significant differences were found over the study period for the severity of drought, as assessed by both the SPI and SPEI. In addition, although in the last 3 decades the mean duration of drought episodes has increased by approximately 1 mo as a consequence of the increase of the PET rates, the differences are not statistically significant. River discharge is mainly driven by precipitation variability, whereas warming processes did not have a noticeable influence on the streamflow variability between 1930 and 2006. The implications of global warming projected by global climate models on future drought severity and the availability of water resources are highly relevant in the near future. ; This study has been supported by the research projects CGL2008-01189/BTE and CGL2006-11619/ HID, financed by the Spanish Commission of Science and Technology; FEDER, EUROGEOSS (FP7-ENV-2008-1- 226487) and ACQWA (FP7-ENV-2007-1-212250), financed by the VII Framework Programme of the European Commission; 'Las sequías climáticas en la cuenca del Ebro y su respuesta hidro lógica' and 'La nieve en el Pirineo aragonés: Distribución espacial y su respuesta a las condiciones climáticas', financed by 'Obra Social La Caixa' and the Aragón Government; and the project INCITE09 383 278 PR, financed by Xunta de Galicia. ; Peer reviewed

In this study we analyze the observed trends for the period 1950-2006 in a number of climate indices related to the occurrence of winter warm events in the Ebro basin, northeast Iberian Peninsula. Climatic simulations using 12 regional climate models (RCMs) from the ENSEMBLES database enable calculation of the multi-model means for the projected evolution of these climatic indices for the time periods 2021-2050 and 2051-2080. The results based on observations indicate a significant increase in occurrence of warm and very warm days and nights, melting events at 2000m a.s.l. and the duration of warm spells across most of the study area. The number of warm spells comprising at least five consecutive warm days or nights also tends to increase, although the trend is not statistically significant for many of the observatories involved in the study. The RCMs project that the trends observed during the observation period will continue, and that the occurrence of warm day and night events and spells are very likely to increase during this century. In some cases the occurrence of warm events is projected to double during the period 2021-2050, and continue increasing for the period 2051-2080. For both the observed and projected periods, most of the indices show a greater increase in the occurrence of these events in the mountain areas of the basin (the Pyrenees and the Iberian mountains). © 2013 Royal Meteorological Society. ; We thank the Agencia Estatal de Meteorología for providing the temperature data used in this study. This work was supported by the research projects CGL2011-27574-CO2-02 and CGL2011-27536, financed by the Spanish Commission of Science and Technology and FEDER; and ACQWA (FP7-ENV-2007-1-212250), financed by the VII Framework Programme of the European Commission; Efecto de los escenarios de cambio climatico sobre la hidrología superficial y la gestión de embalses del PirineoAragonés, financed by Obra Social La Caixa and the Aragón Government and Influencia del cambioclimático en el turismo de nieve CTTP01/10, financed by the Comunidad de Trabajo de los Pirineos. ; Peer Reviewed

This paper evaluates the response of streamflow in a Mediterranean medium-scaled basin under land-use and climate change scenarios and its plausible implication on the management of Boadella–Darnius reservoir (NE Spain). Land cover and climate change scenarios supposed over the next several decades were used to simulate reservoir inflow using the Regional Hydro-Ecologic Simulation System (RHESsys) and to analyze the future impacts on water management (2021–2050). Results reveal a clear decrease in dam inflow (−34%) since the dam was operational from 1971 to 2013. The simulations obtained with RHESsys show a similar decrease (−31%) from 2021 to 2050. Considering the ecological minimum flow outlined by water authorities and the projected decrease in reservoir's inflows, different water management strategies are needed to mitigate the effects of the expected climate change. ; This research was funded by LIFE Programme| EU LIFE (LIFE12ENV/ES/000536). We would like to thank the Spanish Meteorological State Agency (AEMET), the Meteorologica Service of Catalonia (MeteoCat-SMC), and the Agència Catalana del Aigua (ACA) for providing the climatic and streamflow databases used in this study. This work has been supported by research projects: "LIFE12 ENV/ES/000536-Demonstration and validation of innovative methodology for regional climate change adaptation in the Mediterranean area (LIFE MEDACC)", financed by the LIFE programme of the European Commission; PCIN-2015-220 and CGL2014-52135-C03-01, financed by the Spanish Commission of Science and Technology and FEDER; IMDROFLOOD, financed by the Water Works 2014, INDECIS, which is part of ERA4CS, an ERA-NET initiated by JPI Climate and also funded by FORMAS (Sweden), DLR(Germany), BMWFW(Austria), IFD (Denmark), MINECO(Spain), and ANR (France), with co-funding by the European Union (Grant 690462). ; Peer reviewed