Simulating the effects of extreme dry and wet years on the water use of flooding-irrigated maize in a mediterranean landplane

The final editorial version is available at: http://www.sciencedirect.com/science/journal/03783774The effects of years of extreme rainfall events on maize water-use under traditional flooding irrigation in a Mediterranean landplane were estimated through a simulation assessment; combining a weather generator with an agrohydrological simulation model. Two options: “Fully Irrigation” and “Deficit Irrigation” were considered in the simulations as the extreme water-management situations. Besides, a 2-m depth shallow water table and Free Drainage were considered as the typical extreme situations that can be found at the bottom of the simulated soil layer. Thirty “Dry” (DY) and “Wet” (WY) years were randomly selected from the weather generator output. The model SWAP was used to simulate the Relative Transpiration (RT), i.e. ratio between actual and maximum maize transpiration, Actual Maize Evapotranspiration (ETC), Percolated Water and Capillary Rising during wet and dry years and for each of the irrigation and bottom condition options. According to the modelling results, average mean RT is about 80% and 90% in dry and wet years, respectively. RT and ETC variability are very high under dry conditions although such variability is notably reduced if a suitable irrigation option is considered. Capillary rising can play a very important role during dry years in those places where irrigation is not enough, but water table is relatively shallower. On the other hand, a shallower water table can carry out RT reductions during wet years, due to water excess, although these negative effects are comparatively lower than those produced by rain scarcity. Besides, percolated water during wet years is very high, particularly in well irrigated farms.Peer reviewe

Evapotranspiration and crop coefficients of rice (Oryza sativa L.) under sprinkler irrigation in a semiarid climate determined by the surface renewal method

The evapotranspiration (ETc) of sprinkler-irrigated rice was determined for the semiarid conditions of NE Spain during 2001, 2002 and 2003. The surface renewal method, after calibration against the eddy covariance method, was used to obtain values of sensible heat flux (H) from high-frequency temperature readings. Latent heat flux values were obtained by solving the energy balance equation. Finally, lysimeter measurements were used to validate the evapotranspiration values obtained with the surface renewal method. Seasonal rice evapotranspiration was about 750–800 mm. Average daily ETc for mid-season (from 90 to 130 days after sowing) was 5.1, 4.5 and 6.1 mm day−1 for 2001, 2002 and 2003, respectively. The experimental weekly crop coefficients fluctuated in the range of 0.83–1.20 for 2001, 0.81–1.03 for 2002 and 0.84–1.15 for 2003. The total growing season was about 150–160 days. In average, the crop coefficients for the initial (Kcini), mid-season (Kcmid) and late-season stages (Kcend) were 0.92, 1.06 and 1.03, respectively, the length of these stages being about 55, 45 and 25 days, respectively

Effects of water re-allocation in the Ebro river basin: A multiregional input-output and geographical analysis

The quality and availability of water are affected by numerous variables, through which the evaluation of water uses from different perspectives, and policy proposals to save water have now become essential. This paper aims to study water use and the water footprint from a river basin perspective, taking into account regions, sectors, and municipalities, while considering the physical frontier along with the administrative sectors. To this end, we have constructed a multi-regional input-output table for the Ebro river basin, disaggregating the primary sector into 18 different crops and 6 livestock groups. We pay special attention to crop production because it is the most water-consuming industry. The construction of the multi-regional input-output model represents an important contribution to the literature, in itself, since, to the best of our knowledge, it is the first to be built for this large basin. We extend this multi-regional input-output model to assess the water footprint by sectors and regions within the basin. We use these data to propose two scenarios: reallocating final demand to reduce the blue water footprint (scenario 1), and increasing value added (scenario 2). These scenarios outline the opportunity costs of saving water in socioeconomic terms in the basin. In another application, we downscale the multi-regional input-output model results at the municipal level and depict them using a geographical information system, identifying the hotspots and the areas that would pay for the socioeconomic opportunity costs of saving water. Our results suggest that saving 1 hm 3 of blue water could cost around €41, 500 of value added if we consider the entire basin. However, this water re-allocation implies losses and gains at the municipal level: some municipalities would reduce value added by more than €30, 000, while others would gain more than €85, 000 of value added. These tools and results can be useful for policy makers when considering re-allocating water. The contribution and the novelty of this paper is the construction of the multiregional input-output model for the Ebro river basin, and its link with geographical systems analysis at the municipal level

Comparing Penman-Monteith and Priestley-Taylor approaches as reference-evapotranspiration inputs for modeling maize water-use under mediterranean conditions

The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774 http://dx.doi.org/10.1016/j.agwat.2003.12.003A comparison between experimental and simulated data, considering the Priestley-Taylor (PT) and Penman-Monteith (PM) Reference-Evapotranspiration (ET0) approaches was carried out. Experimental data, obtained from an irrigation assessment, conducted during the 1995 and 1996 maize growth-seasons at Zaragoza, Spain, was compared to the mechanistic-model SWAP simulation-results, considering each of the ET0 calculation approaches in the model input. Soil hydraulic properties, meteorological data, seeding and harvest dates, crop water management and other experimental data were used as SWAP input. As corresponding to the windy and dry conditions found in many Mediterranean landplanes, PT ET0 values were significantly lower than PM ET0 calculations. Furthermore, simulated actual evapotranspirations considering the PT approach (PT-ETc) were lower than those found in the simulations that consider the PM approach (PM-ETc). Correspondingly, simulated drainage flux and soil water contents were higher when the PT ET0 approach was used. The correlation coefficients between simulated and measured actual maize evapotranspirations and soil water contents were statistically significant, but the same for both ET0 calculation approaches. Mean and median differences between actual and simulated maize water-use were not statistically different from zero for both considered ET0 calculation approaches. Experimental data variability was significantly higher than simulated variability. The comparisons among the evaluated irrigation options, made with the experimental water-use data, lead almost to the same conclusions than those achieved from the simulated maize water-use. Considering PM-ETc rather than PT-ETc yields no statistical difference in the modeling-based conclusions. According to the obtained results, the PT approach could be used under Mediterranean conditions for comparative assessments aimed to support irrigation decision-making.Peer reviewe

Sprinkler evaporation losses in alfalfa during solid-set sprinkler irrigation in semiarid areas

49 Pags., 3 Tabls., 6 Figs. The definitive version is available at: http://link.springer.com/journal/271Gross sprinkler evaporation losses (SELg) can be large and decrease irrigation application efficiency. However, it is not universally established how much of the SELg contributes to decrease the crop evapotranspiration during the sprinkler irrigation and how much are the net sprinkler losses (SELn). The components of SEL were the wind drift and evaporation losses (WDEL) and the water intercepted by the crop (IL). The gross WDEL (WDELg) and evapotranspiration (ET) were measured simultaneously in two alfalfa (Medicago sativa L.) plots, one being irrigated (moist, MT) and the other one not being irrigated (dry, DT). Catch can measurements, mass gains and losses in the lysimeters and micrometeorological measurements were performed to establish net WDEL (WDELn) during the irrigation and net IL (ILn) after the irrigation as the difference between ETMT and ETDT. Also, equations to estimate ILn and net sprinkler evaporation losses (SELn) were developed. ILn was strongly related to vapor pressure deficit (VPD). SELn were 8.3% of the total applied water. During daytime irrigations, SELn was 9.8% of the irrigation water and slightly less than WDELg (10.9%). During nighttime irrigations SELn were slightly greater than WDELg (5.4% and 3.7%, respectively). SELn was mainly a function of wind speed.This research was funded by the MCINN of the Government of Spain through grants AGL2007-66716-C03-01/02, AGL2010-21681-C03-01/03; the European Commission through grant QUALIWATER (INCO-CT-2005-015031) and by the FPI-MINECO PhD grant program.Peer reviewe

Introducción de herramientas de simulación en la toma de decisiones sobre el manejo del agua frente a condiciones climáticas variables: Retos y oportunidades

11 Pags.- 2 Tabls.- 5 Figs.[ES] Se prevé que el cambio climático ocasionará en los países del Mediterráneo un incremento de las necesidades hídricas de las plantas y menos disponibilidad de agua. Actualmente se cuenta con escenarios climáticos relativamente fiables, así como con herramientas de simulación que permiten estimar las consecuencias de este cambio para sitos particulares. Sin embargo, estas herramientas no han sido aplicadas aún de una manera significativa para apoyar la toma de decisiones agrícolas en España, fundamentalmente porque no son suficientemente conocidas. Se expone un ejemplo de su aplicación, al estimar el efecto del cambio climático en las evapotranspiraciones del maíz bajo riego por inundación en Aragón de 2001 al 2025, a través de la combinación de escenarios climáticos obtenidos del modelo CGCMa1 para el Norte de España, con el generador de tiempo LARS-WG y el modelo agrohidrológico SWAP. Se discuten las características del escenario climático, así como la fiabilidad de las simulaciones con el generador. Se muestra el empleo del modelo de simulación para estimar la evapotranspiración y otros componentes del balance hídrico bajo las condiciones climáticas consideradas. En particular, para las condiciones simuladas, el riego tradicionalmente empleado podría ser suficiente para satisfacer las necesidades hídricas del maíz hasta el 2025, pero las lluvias excesivas, cada vez más frecuentes, pueden provocar disminución de los rendimientos.[EN] Climate change should bring an increment of crop water requirements, as well as a reduction of water availability in the Mediterranean countries. Climate change effects on particular sites can be estimated through present relatively-confident climate scenarios, as well as through currently-available simulation tools. However, such tools have not been significantly applied to support agricultural decision-making in Spain, mainly because they are still rather unknown. An application example is shown, by estimating climate change effects on flooding-irrigated maize evapotranspirations in Aragón from 2001 to 2025. The assessment was made combining climate scenarios obtained from the CGCMa1 model for Northern Spain with the LARS-WG weather generator and the agrohydrological model SWAP. The climate scenario features are discussed, as well as the weather-generator simulations reliability. The simulation model use for estimating evapotranspiration and other water-balance components under the considered climate conditions is shown. Particularly, for the simulated conditions, the traditionally-considered water supply could be enough to satisfy the maize water requirements till 2025. However, the more frequently found heavy rains could give raise to yield reductions.Peer reviewe

Análisis del uso del agua en el sistema de riegos del alto Aragón combinando el sistema ADOR y teledetección

10 Pags., 2 Tabls., 3 Figs.[ES] En este trabajo se presenta una metodología para la evaluación del aprovechamiento del agua de riego a escala regional. Esta metodología se basa en el uso de los datos procedentes del sistema de gestión de riego Ador, y en la aplicación de técnicas de teledetección. Dichas técnicas permiten estimar: 1) el patrón de cultivos mediante clasificación supervisada; y 2) el consumo de agua de los cultivos mediante balance de energía (modelo ReSET-Raster). La aplicación de esta metodología a la zona regable de Riegos del Alto Aragón (125.899 ha) cuantificó las diferencias entre los aprovechamientos potencial y real del agua en las condiciones del periodo de estudio: (2004 y 2005). Asimismo, se identificaron aquellas comunidades de regantes en las que esas diferencias fueron mayores. En general, estas diferencias fueron menores en condiciones de sequía como las de 2005. Este año presentó un valor de suministro relativo de agua de 0,99, frente a 1,30 en 2004, aunque la producción agrícola disminuyó un 20% respecto a 2004. Asimismo, las comunidades con tecnologías de riego más avanzadas también presentaron menores diferencias. Sin embargo, el consumo de agua fue un 21% mayor en estas comunidades en ambos años.[EN] This work presents a methodology focused on the assessment of irrigation water use at regional scale. This methodology is based on data provided by the irrigation management system named Ador and remote sensing techniques. These techniques allow estimating: 1) the crop pattern through supervised classification; and 2) the crop water consumption through energy balance (ReSET-Raster model). Gap between potential and real water use was computed in the Riegos del Alto Aragón irrigation project (125.899 ha) applying this methodology during 2004 and 2005. Those irrigation districts presenting the largest gap were identified. Overall, this gap was lower during drought events (2005). Relative water supply was 0,99 in 2005 and 1,30 in 2004, although agricultural production plunged 20% in 2005 with respect to 2004. Additionally, this gap was lower for irrigation districts using modern irrigation technologies. However, water consumption was about 21% higher in these districts in both years.Este trabajo ha sido financiado por la Fundación Agencia Aragonesa para la Investigación y el Desarrollo (ARAID) a través de la convocatoria “Jóvenes Investigadores 2010” ARAID-IberCaja. La beca predoctoral de I. Chalghaf y el contrato de investigación de S. Lecina han sido financiados por el Instituto Nacional de Investigación y Tecnología Agraria y Agroalimentaria (INIA).Peer reviewe

Seasonal on-farm irrigation performance in the Ebro basin (Spain): Crops and irrigation systems

Irrigation performance assessments are required for hydrological planning and as a first step to improve water management. The objective of this work was to assess seasonal on-farm irrigation performance in the Ebro basin of Spain (0.8 million ha of irrigated land). The study was designed to address the differences between crops and irrigation systems using irrigation district data. Information was only available in districts located in large irrigation projects, accounting for 58% of the irrigated area in the basin. A total of 1617 records of plot water application (covering 10,475 ha) were obtained in the basin. Average net irrigation requirements (IRn) ranged from 2683 m3 ha-1 in regulated deficit irrigation (RDI) vineyards to 9517 m3 ha-1 in rice. Average irrigation water application ranged from 1491 m3 ha-1 in vineyards to 11,404 m3 ha-1 in rice. The annual relative irrigation supply index (ARIS) showed an overall average of 1.08. Variability in ARIS was large, with an overall standard deviation of 0.40. Crop ARIS ranged between 0.46 and 1.30. Regarding irrigation systems, surface, solid-set sprinkler and drip irrigated plots presented average ARIS values of 1.41, 1.16 and 0.65, respectively. Technical and economic water productivities were determined for the main crops and irrigation systems in the Aragón region. Rice and sunflower showed the lowest productivities. Under the local technological and economic constraints, farmers use water cautiously and obtain reasonable (yet very variable) productivities.ARIS Regulated deficit irrigation Surface irrigation Sprinkler Drip Irrigation requirements

Evaluation of satellite evapotranspiration estimates using ground-meteorological data available for the Flumen District into the Ebro Valley of N.E. Spain

The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774Accurate estimation of actual evapotranspiration (ETa) is essential for effective local or regional water management. At a local scale, ET estimates can be made accurately considering a soil–plant-atmospheric system, if adequate meteorological-ground data or ET measurements are available. However, at a regional scale, ETa values cannot be measured directly and the estimates are frequently subject to errors. Although it is possible to extrapolate to the regional scale from local (point) data of meteorological stations, the relative sparse coverage of ground estimate can make this problematic without some spatial analysis to demonstrate the similarity of the climate in the area. The introduction of remote sensing data and techniques offers alternatives both to estimate variables (i.e. radiation) and parameters (i.e. ET) with few spatial restrictions, thus, it provides potential advantages to the regional ETa computation. In particular, the use of remote sensing procedures like the surface energy balance-based algorithms (SEB) have been successfully applied in different climates, enabling the estimation of ETa at local and regional scales. A proper variation of the Surface Energy Balance Algorithm for Land (SEBAL) was applied to 4 years of data for the Flumen District in the Ebro Basin at the N.E. of Spain. Results obtained show that the remote sensing algorithm can provide accurate daily ETa estimations as compared with lysimeter measurements of daily ET values for two crop plots: one with a reference grass and other with maize or wheat as function of the season. Also a comparison between ETa and the reference and crop ET values applying the Penman–Monteith method was carried out. The comparison analysis consider an accepted error difference of 1.0 mm d−1 (20% of error) for local scale, the ETa values for the grass show a bias of 0.30 mm d−1 against the ETgrass and a bias of 0.36 mm d−1 against ETo. Differences between ETmaize or ETwheat and ETa against their average showed an acceptable agreement for the field with sdiff ± 0.6 mm d−1. For the crop fields at regional scale external causes associated to atmospheric and surface variations (i.e. land preparation) rather to the remote sensing algorithm made difficult to determine a percentage of error. Finally, ETa values were obtained at regional scale and it was demonstrated that using the remote sensing improve significantly the crop ET estimations computed in the area using traditional methods.The authors gratefully acknowledge the financial support of DGAPA-UNAM and CONACyT, Mexico.Peer reviewe