Process-based hydrologic models allow to identify the behavior of a basin providing a mathematical description of the hydrologic processes underlying the runoff mechanisms that govern the streamflow generation. This study focuses on a macroscale application of the Variable Infiltration Capacity (VIC) model over 31 headwater subwatersheds belonging to the Duero River Basin, located in the Iberian Peninsula, through a threepart approach: (1) the calibration and validation of the VIC model for all the subwatersheds; (2) an integrated sensitivity analysis concerning the soil parameters chosen for the calibration, and (3) an assessment of equifinality and the efficiency of the calibration algorithm. The calibration and validation processes showed good results for most of the subwatersheds in a computationally efficient way using the Shuffled-Complex-Evolution algorithm. The sensitivity measures were obtained with the Standardized Regression Coefficients method through a post-process of the outputs of a Monte Carlo simulation carried out for 10 000 parameter samples for each subwatershed. This allowed to quantify the sensitivity of the water balance components

The Weather Research and Forecasting (WRF) model has been used to show the benefits provided by downscaled fields to detect and analyze wet and dry periods over a region with high precipitation variability such as Spain. We have analyzed the spatiotemporal behavior of two widely used drought indices: the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI), computed at 3 and 12 month time scales, which provide important information in an agricultural and water‐resource context. These two indices were computed from WRF outputs and compared with those calculated from observational (monthly precipitation and temperature databases of Spain, MOPREDAS and MOTEDAS) and from the European Centre for Medium‐Range Weather Forecasts Interim Re‐Analysis (ERA‐Interim) data sets. This evaluation was made by using a regional scale and a multistep regionalization method and by comparison of individual grid points. In general, results indicate that the drought indices obtained by using WRF outputs provide a noticeable improvement regarding those computed by using ERA‐Interim, higher at longer time scales. Although results show no significant differences between drought indices analyzed, the improvement offered by WRF is greater for SPI than for SPEI. In terms of averaged duration, magnitude, and severity of drought, the benefits provided by WRF are not so evident, presenting better agreement with the observational data at 12 month time scale, being clearer for the intensity. These findings evidence the benefit of using WRF climate fields to monitor, analyze, and detect drought events, being a valuable source of knowledge for a suitable decision making, especially for water‐resource management.

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This study presents a basin‐wide assessment about the spatiotemporal variability of streamflows in Ecuador for the period 1979–2015. The influence of the tropical Pacific sea surface temperature (SST) on streamflow variability from February to April (FMA) period, as the months showing maximum streamflow for the wet season in Ecuador, and from June to August (JJA), corresponding to the dry season, was analysed. First, a long‐term trend analysis was carried out by applying the Sen's slope estimator and the Mann–Kendall test to monthly streamflow data from 45 gaging stations located in different basins across Ecuador. While the coastal region showed the highest generalized positive trends from July to January, the results for the Pacific Andean area suggested a strengthening of the seasonality, presenting an overall increase in the streamflow for all months except August, September and October, which showed negative trends. Second, a singular‐value decomposition (SVD) was applied in order to find the main coupled variability patterns between the FMA streamflow and the quasi‐coetaneous SST (December–February [DJF]) and between the JJA streamflow and the coetaneous SST. The results revealed two main coupled modes for DJF SST/FMA streamflow, the first associated with the canonical El Niño and the second with El Niño Modoki. The latter exerted a major influence on FMA streamflow over most of Ecuador. For JJA streamflow, however, the pattern associated with the traditional El Niño was even more relevant. These results establish the foundations for streamflow modelling in Ecuador based on the Pacific SST, showing the strong response of the streamflows to different types of El Niño events.

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The analysis and understanding of drought phenomenon are essential for the management of hydrological resources. Drought indices are commonly used to predict these extreme events, being their suitability partly due to the use of climate fields at an adequate spatiotemporal resolution. This work aims to examine spatiotemporal patterns of drought over the Iberian Peninsula (IP), which is a region especially vulnerable to drought phenomenon. For this, climate data from a simulation completed with the Weather Research and Forecasting (WRF) model have been used. The spatiotemporal patterns of drought over the period 1980-2014 were examined using the Standardized Precipitation Evapotranspiration Index (SPEI) at the 3-and the 12-month time scales, and they were compared with other droughtrelated variables such as the surface evapotranspiration (SFCEVP), soil moisture (SM), and runoff. The results evidence that WRF is a valuable tool for characterizing droughts over the IP, providing large amounts of climate data at an adequate spatial resolution. Drought events seem to be more severe in regard to their duration over southern IP. Moreover, a good agreement between the SPEI at 3-month time scale with the SM and the SFCEVP is found. Additionally, the annual runoff evolves similarly to the SPEI at 12-month time scale.