This paper analyzes the validity of various precipitation and temperature maps obtained by means of diverse interpolation methods. The study was carried out in an area where geographic differences and spatial climatic diversity are significant (the middle Ebro Valley in the northeast of Spain). Two variables, annual precipitation and temperature, and several interpolation methods were used in the climate mapping: global interpolators (trend surfaces and regression models), local interpolators (Thiessen polygons, inverse distance weighting, splines), geostatistical methods (simple kriging, ordinary kriging, block kriging, directional kriging, universal kriging and co-kriging) and mixed methods (combined global, local and geostatistical methods). The validity of the maps was checked through independent test weather stations (30% of the original stations). Different statistical accuracy measurements determined the quality of the models. The results show that some interpolation methods are very similar. Nevertheless, in the case of precipitation maps, we obtained the best results using geostatistical methods and a regression model formed by 4 geographic and topographic variables. The best results for temperature mapping were obtained using the regression-based method. The accuracy measurements obtained by the different interpolation methods change significantly depending on the climatic variable mapped. The validity of interpolation methods in the creation of climatic maps, useful for agricultural and hydrologic management, is discussed.

Abstract. The influence of climate variation on the availability of water resources was analyzed in 15 the headwaters of the Tagus River basin using two drought indices, the standardized precipitation 16 index (SPI) and the standardized precipitation evapotranspiration index (SPEI). This basin is highly 17 regulated and strategic, and contains two hyperannual reservoirs that are the origin of the water 18 supply system for Mediterranean areas of southeast Spain. The indices confirmed that drought 19 conditions have prevailed in the headwaters of the Tagus River since the 1970s. The responses in 20 river discharge and reservoir storage were slightly higher when based on the SPEI rather than the 21 SPI, which indicates that although precipitation had a major role in explaining temporal variability 22 in the analyzed parameters, the influence of temperature was not negligible. Moreover, the greatest 23 response in hydrological variables was evident over longer timescales of the climatic drought 24 indices. Although the effect of climate variability on water resources was substantial during the 25 analyzed period, we also showed a major change in hydrological-climatic relationships in regulated 26 systems including reservoir storage and outflow. These were closely related to changes in external 27 demand following commencement of the water transfer system to the Júcar and Segura basins after 28 the 1980s. The marked reduction in water availability in the basin, which is related to more frequent 29 droughts, contrasts with the amount of water transferred, which shows a clear upward trend 30 associated with increasing water demand in the Mediterranean basin. 31 32 33

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Droughts are a recurrent phenomenon in the Mediterranean basin with negative consequences for society, economic activities, and natural systems. Nevertheless, the study of drought recurrence and severity in Spain has been limited so far due to the relatively short instrumental period. In this work, we present a reconstruction of the standardized precipitation index (SPI) for the Iberian Range. Growth variations and climatic signals within the network are assessed developing a correlation matrix and the data combined to a single chronology integrating 336 samples from 169 trees of five different pine species distributed throughout the province of Teruel. The new chronology, calibrated against regional instrumental climatic data, shows a high and stable correlation with the July SPI integrating moisture conditions over 12 months forming the basis for a 318-year drought reconstruction. The climate signal contained in this reconstruction is highly significant (p<0.05) and spatially robust over the interior areas of Spain located above 1000 meters above sea level (masl). According to our SPI reconstruction, seven substantially dry and five wet periods are identified since the late seventeenth century considering ≥±1.76 standard deviations. Besides these, 36 drought and 28 pluvial years were identified. Some of these years, such as 1725, 1741, 1803, and 1879, are also revealed in other drought reconstructions in Romania and Turkey, suggesting that coherent larger-scale synoptic patterns drove these extreme deviations. Since regional drought deviations are also retained in historical documents, the tree-ringbased reconstruction presented here will allow us to crossvalidate drought frequency and magnitude in a highly vulnerable region.

Abstract. Among the different meteorological hazards,