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The Tagus River basin is an ultimately important water source for hydropower production, urban and agricultural water supply in Spain and Portugal. Growing electricity and water supply demands, over-regulation of the river and construction of new dams, as well as large inter-basin and intra-basin water transfers aggravated by strong natural variability of climate in the catchment, have already imposed significant pressures on the river. The substantial reduction of discharge is observed already now, and projected climatic change is expected to alter the water budget of the catchment further.In this study, we address the effects of projected climate change on the water resources availability in the Tagus River basin and influence of potential changes on hydropower generation of the three important reservoirs in the basin. The catchment-scale, process-based eco-hydrological model soil and water integrated model was set up, calibrated and validated for the entire Tagus River basin, taking into account 15 large reservoirs in the catchment. The future climate projections were selected from those generated within the Inter-Sectoral Impact Model Intercomparison Project. They include five bias-corrected climatic datasets for the region, obtained from global circulation model runs under two emissions scenario - moderate and extreme ones - and covered the whole century. The results show a strong agreement among model runs in projecting substantial decrease of discharge of the Tagus River discharge and, consequently, a strong decrease in hydropower production under both future climate scenarios. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this study, the water draining a catchment of 65 km in NW Spain was monitored over a 3-year period to examine temporal variability of five metal concentrations (Al, Fe, Mn, Cu, and Zn) in dissolved form and also in suspended solids (SS), under two different hydrological conditions-in baseflow and stormflow events. pH, SS and dissolved organic carbon (DOC) were also examined as possible factors affecting metal transport mechanisms. The results showed that Al, Cu, and Zn were significantly ( p < 0.05) higher in stormflow events than in baseflow, while in SS, all metal concentrations decreased ( p < 0.05) during stormflow events. The metal seasonal variability was also examined. In dissolved form, only Fe showed significant differences ( p < 0.05) between seasons, with higher concentrations in summer, independently of the hydrological conditions, while in SS, only Cu during stormflow events showed concentrations significantly higher ( p < 0.05) during summer than in the remainder seasons. The partition coefficients ( K) decreased significantly ( p < 0.05) for all metals during stormflow events. K correlations showed that SS and DOC were the main factors in controlling the K of all metals, except the K of Mn which did not depend on any of these variables in baseflow. Metal enrichment factors were significantly higher ( p < 0.05) during baseflow than in events which were associated to SS source and size. [ABSTRACT FROM AUTHOR]

Summary: In this study we analyzed the response of monthly runoff to precedent climatic conditions at temporal scales of 1–48months in 88 catchments of the Ebro basin (northeast Spain). The standardized precipitation evapotranspiration index (SPEI) was used to summarize the climatic conditions at different time scales, and was correlated with the standardized streamflow index (SSI) calculated at the mouth of each catchment. The Ebro basin encompasses a gradient from Atlantic to Mediterranean climates, and has remarkable complexity in topography, geology and land cover. The basin is highly regulated by dams, which were built to produce hydropower and supply water for agriculture. These characteristics explain why sub-basins of the Ebro River basin respond in differing ways to precedent climatic conditions. Three main sub-basin groups were distinguished on the basis of the correlation of their streamflow responses to different time scales of the SPEI: (1) sub-basins correlated with short SPEI time scales (2–4months), which generally corresponded to unregulated headwater areas; (2) sub-basins correlated with long SPEI time scales (10–20months), where groundwater reserves play a major hydrological role; and (3) sub-basins correlated with medium SPEI time scales (6–10months). The latter occur in the lower sectors of the Ebro basin and its tributaries, which receive river flows from the other two sub-basins, and where dam regulation has a significant influence on the hydrological characteristics. In addition to the three main sub-basin groups, other streamflow responses associated with seasonal factors were identified, particularly those related to snowpack and the various management strategies applied to reservoirs. [ABSTRACT FROM AUTHOR]

Abstract: To evaluate the vulnerability of agriculture under Mediterranean conditions, the real water needs of agriculture in the Fluvià watershed (Catalonia, NE Spain) were estimated for the XXIst century using a combination of downscaled climate projections (ECHAM5 plus MM5) in two IPCC scenarios (B1 and A2), watershed hydrological model (SWAT) and FAO procedure to calculate crop potential evapotranspiration. In comparison with baseline conditions (1984–2008), climate projections predicted a 12% (B1) to 28% (A2) reduction in precipitation, and a 2.2°C (B1) to 3.6°C (A2) increment of mean annual temperature at the end of the XXI Century (2076–2100). The changes of the environmental conditions would affect the real water availability in different crops: water required for irrigation would increase significantly along the century, ranging from 40 to 250% depending on the crop, because of a direct decrease in the amount of water available along the growing season and because of the effects of the projected climatic conditions on potential evapotranspiration (ET0) and on the phenology of these crops. Results are showing the high sensitivity of agriculture, despite its expanding technology, to changes in climate, and even more to site, plot, orchard or terroir conditions. [Copyright &y& Elsevier]

Climate change, drought and the world's growing population are increasing the demand for water which in turn requires improved water resources management. The sustainable management of a watershed requires a thorough knowledge of its water resources, including monthly streamflow. Spain is home to a large number of ungauged watersheds, the streamflows of which are often unknown. Chavez et al. (2007) reported a model for predicting monthly streamflow in ungauged watersheds that was validated for use in areas of tropical climate in Central America and a dry area in South America. This work reports an attempt to assess the performance of this model for eventual use with ungauged watersheds in Spain, using data for a number of watersheds for which gauging data were available. The proposed model took into account physical characteristics such us the soil infiltration rate, the slope of the terrain, plant fractional cover, the monthly moisture adequacy index, and the leaf area index. Comparisons of model-predicted monthly streamflows and those actually measured showed the Chavez et al. model unable to make reliable predictions for Spanish watersheds in its current form. A new approach has been developed considering only smaller watersheds in Spanish conditions, changing parameters in the original model. These parameters have been calibrated and validated, reaching adequate adjustment of results. [ABSTRACT FROM AUTHOR]

Summary: A methodology to analyze impact, vulnerability and adaptation to climate change in conjunctive-use systems at basin scale is presented. Based on the value obtained for various indices under possible future scenarios (indices obtained from the results of a system management model), a systematic procedure is presented to identify problems and solutions to adapt to climate change effects. The future hydrological scenarios to be analyzed can be approached by starting from the historical series available for the system and taking into account the changes expected in the key statistics of the series. A method to predict the expected changes in the key statistics using the results of previous climate change studies in the area has been developed. A “downscaling” procedure is proposed to translate the climatic variations into results on a basin scale. The methodology has been applied to the case study of the Serpis River Basin (Eastern Spain). [ABSTRACT FROM AUTHOR]

The impact of climate change and its relation with evapotranspiration was evaluated in the Duero River Basin (Spain). The study shows possible future situations 50 yr from now from the reference evapotranspiration (ETo). The maximum temperature (Tmax), minimum temperature (Tmin). dew point (Td), wind speed (U) and net radiation (Rn) trends during the 1980-2009 period were obtained and extrapolated with the FAO-56 Penman-Montheith equation to estimate ETo. Changes in stomatal resistance in response to increases in CO2 were also considered. Four scenarios were done, taking the concentration of CO2 and the period analyzed (annual or monthly) into consideration. The scenarios studied showed the changes in ETo as a consequence of the annual and monthly trends in the variables Tmax, Tmin, Td, U and Rn with current and future CO2 concentrations (372 ppm and 550 ppm). The future ETo showed increases between 118 mm (11%) and 55 mm (5 %) with respect to the current situation of the river basin at 1042 mm. The months most affected by climate change are May, June, July, August and September, which also coincide with the maximum water needs of the basin's crops. [ABSTRACT FROM AUTHOR]

Climate change implies changes in the frequency and magnitude of flood events. The influence of climate variability on flooding was evaluated by an analysis of sedimentary (palaeofloods) and documentary archives. A 500-year palaeoflood record at Montlleó River (657 km2 in catchment area), eastern Spain, revealed up to 31 palaeofloods with a range of discharges of 20–950 m3 s−1, and with at least five floods exceeding 740–950 m3 s−1. This information contrasts with the available gauged flood registers (since year 1971) with an annual maximum daily discharge of 129 m3 s−1. Our palaeoflood dataset indicates flood cluster episodes at (1) 1570–1620, (2) 1775–1795, (3) 1850–1890, and (4) 1920–1969. Flood rich periods 1 and 3 corresponded to cooler than usual (about 0.3 °C and 0.2 °C) climate oscillations, whereas 2 and 4 were characterised by higher inter-annual climatic variability (floods and droughts). This high inter-annual rainfall variability increased over the last 150 years, leading to a reduction of annual maximum flow. Flood quantiles (>50 years) calculated from palaeoflood+gauged data showed 30%–40% higher peak discharges than those using only instrumental records, whereas when increasing the catchment area (1500 km2) the discharge estimation variance decreased to ~15%. The results reflect the higher sensitivity of small catchments to changes on flood magnitude and frequency due to climate variability whereas a larger catchment buffers the response due to the limited extent of convective storms. Our findings show that extended flood records provide robust knowledge about hazardous flooding that can assist in the prioritization of low-regret actions for flood-risk adaptation to climate change. [ABSTRACT FROM AUTHOR]