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45 Pags.- 12 Figs.- 4 Tabls. The definitive version is available at: https://www.sciencedirect.com/science/journal/03783774, he impact of zebra mussel (Dreissena polymorpha) colonization on pressurized irrigation systems is becoming important in many areas of the world. If the infestation is not controlled, the conveyance capacity of the network reduces and mussels can completely block the system, preventing irrigation. A methodology to assess zebra mussel infestation in collective pressurized networks based on monitorization and hydraulic simulation is developed in this research. Normalized pressure, defined as the difference between simulated and measured pressure, is an indicator of the presence of zebra mussels (Morales-Hernández et al., 2018). When this variable is combined with the distributed discharge of the irrigation network, it is possible to use an optimization procedure to produce a roughness map of network pipelines. Roughness in excess of that characteristic of the pipeline material can be directly associated zebra mussel infestation. Different objective functions, optimization algorithms and strategies are proposed in this work, with the aim of attaining constant discharge-independent normalized pressure at each observation point in the network. Roughness values under different pipe conditions, reproducing levels of zebra mussel infestation, were experimentally obtained at a reference laboratory. The limitations and uncertainties of the proposed methodology are discussed. Normalized pressure was validated in an irrigation network belonging to a water users association, using continuous data recorded at different observation points during a complete irrigation campaign. The non-invasive hydraulic method has been designed to identify infested areas in real time and to optimize the chemical treatments controlling mussel development, This work was supported by the State Agency of Research of the Government of Spain (Agencia Estatal de Investigación) through grant AGL2017-89407-R and by the European Agricultural Fund for Rural Development (EAFRD) and the Government of Aragón. Both institutions funded the IRRIZEB II (Programa integral para el control y mitigación del impacto de la plaga de Mejillón Cebra en sistemas de regadío II) grant of the Plan de Desarrollo Rural (PDR).

42 Pags.- 4 Tabls.- 11 Figs. The definitive version is available at: https://www.sciencedirect.com/science/journal/03783774, Zebra mussel (Dreissena polymorpha) colonies are becoming a real problem in pressurized irrigation networks. The zebra mussel infestation of the 45 Water Users Associations (WUAs) of the Riegos del Alto Aragón (RAA) irrigation project (121 thousand hectares located in northeastern Spain) was assessed during the period of 2013–2017. Maps of WUA infestation stages were produced. A survey of the WUAs made it possible to assess the relevance of certain structural and management practices in the control of zebra mussels. A method to monitor zebra mussel colonization of pressurized collective irrigation networks was presented. The method is based on the combination of pressure measurements at network hydrants and hydraulic simulations. Normalized pressure, estimated as the difference between simulated and observed pressure, should approach zero in all hydrants in a properly characterized, non-infested network. A positive normalized pressure can indicate the presence of zebra mussel colonies. The methodology was validated using two different test cases located in two RAA WUAs: the first case involved a discrete chemical treatment, while the second case was based on the analysis of three years of telemetry pressure data and remote operation of network hydrants. The existence of an infested reservoir upstream of the WUAs was the most likely source of zebra mussel colonization of the WUA pressurized networks in the RAA project. The desiccation and chemical treatment of the small WUA reservoirs was associated with pest control. The hybrid (measurement-simulation) methodology is able to characterize the presence of zebra mussel colonies in specific reaches of pressurized irrigation networks., This work was supported by the European Agricultural Fund for Rural Development (EAFRD) and by the Government of Aragón. Both institutions funded the IRRIZEB (Programa integral para el control y mitigación del impacto de la plaga de Mejillón Cebra en sistemas de regadío) grant of the Plan de Desarrollo Rural (PDR).

34 Pags.- 7 Tabls.- 1 Fig. The definitive version is available at: https://www.sciencedirect.com/science/journal/03783774, A decades-long policy for irrigation Telemetry and Remote Control (TM/RC) systems in Spain has led to installations for approximately 260 Water Users Associations (WUAs), with a total estimated area of 1.0 M ha of agricultural land. This is believed to be the largest deployment of such technologies in the world. These systems have been installed in financial cooperation between public administrations and WUAs. This paper set out to characterize these systems, assess the causes for their individual success or failure, consider their future evolution and support policy updates. A survey with 110 questions was addressed to 84 WUAs distributed throughout the country. Further, an interview with four questions was addressed to 24 selected stakeholders intervening in irrigation TM/RC projects: from policy makers to farmers. The results provide a detailed overview of these systems in Spain, characterizing the WUAs in which they are installed, their technological traits, their maintenance, the problems they face in their daily operation, their current use, the factors limiting wider use, and the willingness of the WUAs to continue bearing the costs to use TM/RC features in the future. A large majority of TM/RC systems are regularly used to improve WUA water and energy management, and receive proper maintenance. However, in 15% of WUAs, farmers are not satisfied with the TM/RC system, and in 19% of the WUAs the TM/RC system cannot operate half of the hydraulic valves connected to them. We found that early technology applications failed more than recent applications, evidencing a process of technological maturity. The standardization of TM/RC systems, adaptation of the system to WUA specificities, training of WUA personnel, and a sufficiently long guarantee period stood as critical variables for success in the implementation of these technologies., This work was supported by the Spanish State Research Agency (Agencia Estatal de Investigación) of the Ministry of Economy and Competitiveness (MINECO) of the Government of Spain, grant numbers: AGL2013-48728-C2-1-R, AGL2014-59747-C2-1- R, AGL2014-59747-C2-2-R, RTC-2015-3453-2 and RTC-2016-4972-2.

51 Pags.- 4 Tabls.- 12 Figs. The definitive version is available at: https://www.sciencedirect.com/science/journal/03783774, Reducing the working pressure at the sprinkler nozzles is one of the alternatives to reduce energy requirements in solid-set sprinkler irrigation systems. Previous studies reported ≈10% lower seasonal Christiansen uniformity coefficient (CUC) for low-pressure treatments than for standard treatments, but no differences in maize yield. This research analyses the effect of maize canopy water partitioning on irrigation performance indexes (CUC and wind drift and evaporation losses, WDEL). Three irrigation treatments were considered, based on the working pressure: 1) A standard brass impact sprinkler operating at a pressure of 300 kPa (CIS300); 2) A standard brass impact sprinkler operating at a pressure of 200 kPa (CIS200); and 3) A modified plastic impact sprinkler (with a deflecting plate attached to the drive arm) operating at a pressure of 200 kPa (DPIS200). Irrigation performance was measured using a catch-can network located above the maize canopy (CUCac, WDELac) along the whole crop season and using stemflow and throughfall devices below the maize canopy (CUCbc, WDELbc) in eight irrigation events. Maize growth, yield and its components were measured. Under low-wind and fully developed canopy conditions (a frequent situation for maize irrigation), CUCbc resulted higher than CUCac for the low-pressure treatments, while the opposite was observed for the standard pressure treatment. Maize canopy partitioning reduces the differences in irrigation performance indexes between pressure treatments, explaining why there are no differences in grain yield between them. Caution should be used when measuring sprinkler irrigation performance above tall canopies, since the elevation of the catch-cans and the crop canopy partitioning affect performance estimations., This research was funded by the Minister of Economy, Industry and Competitiveness (MICINN) of the Government of Spain through grant AGL2013-48728-C2-1-R. Octavio Robles has a scholarship funded by the Minister of Economy and Competitiveness of the Spanish Government.

The large diversity of irrigated agricultural areas hinders the development of social consensus and complicates decision-making about the allocation of investments for irrigation modernization. A classification of irrigated areas permits the identification and mapping of different categories and reveals the strengths and weaknesses of each category regarding specific criteria. This paper proposes a binomial (genus and species) classification methodology of irrigated areas, which was designed based on a participatory approach. Four internal properties determine the genus: type of water source, type of water energy, on-farm irrigation method and water availability. Four external properties classify the variability within each genus into species: land tenure, crop type, existence of an environmental protection figure and socio-economic level. The words used for the genus and specific name arise from the concatenation of syllables representing the state or level of each property. The method was applied to the irrigated area of the Ebro river basin in the Aragón region of Spain (ERB-Aragón). A total of 435,851 ha were classified. A large part of the irrigated land uses surface water (94 %), does not have water availability problems (80 %), is not affected by environmental protection figures (97 %), is devoted to field crops (86 %), and manifests a low (45 %) or moderate (41 %) socio-economic level. A total of 24 genera and 126 species were identified. The two most representative genera are SurGraFloVe (31 %) and SurPumPreVe (27 %), and the two main species are SurGraFloVe DisCeNoLo (19 %) and SurPumPreVe ConCeNoMo (19 %). These species received the local names of “Ribera del Ebro” and “Alto Aragonés” to facilitate policy discussions. The application of the method to the ERB-Aragón provides a privileged insight that can support policy analyses and guide institutional intervention. The proposed methodology can be adapted to other areas of the world by adjusting criteria and categories to local conditions., This research was funded by the Department of Agriculture, Livestock and Environment of the Regional Government of Aragón through the Rural Development Programme grant GGO2017E03200.

42 Pags.- 5 Tabls.- 8 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, Water and energy are limited and expensive resources. Conserving water and energy is a requirement to ensure the viability of modern pressurized irrigation systems. The objective of this research was to analyze the possibilities of reducing the nozzle operating pressure of impact sprinklers from 300 kPa (standard pressure) to 200 kPa (low pressure) in solid-set irrigation systems without reducing the sprinkler spacing and maintaining crop yield. Three treatments resulting from combinations of sprinkler type, and working pressure were analyzed: 1) Conventional impact sprinkler operating at 300 kPa (CIS300); 2) Conventional impact sprinkler operating at 200 kPa (CIS200); and 3) Modified deflecting plate impact sprinkler operating at 200 kPa (DPIS200). A randomized experimental design was applied to a maize crop during two seasons (2015 and 2016). Irrigation performance was measured by catch-can monitoring at one replicate of each treatment. Maize growth, yield and its components were measured. Differences between treatments in soil water, maize growth and yield variables were analyzed using ANOVA. Seasonal irrigation uniformity evaluated at the top of the canopy was larger for the standard pressure treatment (93%) than for the low pressure treatments (82% and 84% for DPIS200 and CIS200, respectively). The average wind drift and evaporation losses for the 2016 irrigation season were higher for the CIS300 treatment (17%) than for the low pressure treatments, DPIS200 (15%) and CIS200 (13%). Low pressure treatments did not reduce grain yield compared with the standard pressure treatment. Differences in irrigation performance and maize yield between the low pressure treatments, DPIS200 and CIS200, were not statistically significant. The reduction in energy use by reducing the operating pressure from 300 kPa to 200 kPa would allow to increase the net farming benefit of individual and collective systems. This is particularly true if low pressure irrigation is considered at the design phase of the irrigation system., This research was funded by MICINN of the Government of Spain through grant AGL2013-48728-C2-1-R. Octavio Robles has a scholarship funded by the Minister of Economy and Competitiveness of the Spanish Government.

44 Pag., 3 Tabl., 3 Fig. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, This study analyzes the effects of irrigation modernization on water conservation, using the Riegos del Alto Aragón (RAA) irrigation project (NE Spain, 123354 ha) as a case study. A conceptual approach, based on water accounting and water productivity, has been used. Traditional surface irrigation systems and modern sprinkler systems currently occupy 73% and 27% of the irrigated area, respectively. Virtually all the irrigated area is devoted to field crops. Nowadays, farmers are investing on irrigation modernization by switching from surface to sprinkler irrigation because of the lack of labour and the reduction of net incomes as a consequence of reduction in European subsidies, among other factors. At the RAA project, modern sprinkler systems present higher crop yields and more intense cropping patterns than traditional surface irrigation systems. Crop evapotranspiration and non-beneficial evapotranspiration (mainly wind drift and evaporation loses, WDEL) per unit area are higher in sprinkler irrigated than in surface irrigated areas. Our results indicate that irrigation modernization will increase water depletion and water use. Farmers will achieve higher productivity and better working conditions. Likewise, the expected decreases in RAA irrigation return flows will lead to improvements in the quality of the receiving water bodies. However, water productivity computed over water depletion will not vary with irrigation modernization due to the typical linear relationship between yield and evapotranspiration and to the effect of WDEL on the regional water balance. Future variations in crop and energy prices might change the conclusions on economic productivity.

The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, In the last decade irrigation districts in the Ebro Valley of Spain have started to use database applications to enhance their management operations. Such applications often put more emphasis on administrative issues than on water management issues. A new irrigation district management software called “Ador” is presented in this paper. This database application has been designed to overcome limitations identified in an analysis of the software used in the study area. Ador can be used in irrigation districts independently of the type of irrigation system (surface, sprinkler or trickle) and the type of irrigation distribution network (open channel or pressurised). It can even be used in irrigation districts combining different types of irrigation systems and different types of irrigation distribution networks. The software can be used with minimum district information. The goals are to manage detailed information about district water management and to promote better on-farm irrigation practices. Ador is currently used to enhance management of 62 irrigation districts accounting for some 173,000 hectares in the Ebro Valley., National Plan for Research and Development of the Government of Spain (AGL2000-0151-P4-02). FEDER II of the European Union (2FD97-0547-C02). I3P program of the European Union. Oficina del Regante (Government of Aragón, FEOGA funds of the European Union).

32 Pags.- 3 Tabls.- 7 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, In this work, a Fixed Spray Plate Sprinkler (FSPS) and two Rotating Spray Plate Sprinklers (RSPS) were compared in terms of wetted diameter, wind drift and evaporation losses (WDEL), static water precipitation pattern and dynamic water application profile. An experimental irrigation machine reproducing a pivot section was constructed and used to perform experiments in static and dynamic (linear displacement) modes. Water application from FSPS often resulted in a bi-modal pattern, while RSPS produced bell-shaped or triangular patterns. At a nozzle elevation of 2.4 m and an operating pressure of 140 kPa the wetted diameter was 1.6 m larger for the RSPS than for the FSPS. The differences between the two RSPS amounted to 0.5 m on the average. Reducing the nozzle elevation from 2.4 to 1.0 m resulted in a 2.6 m decrease in the wetted diameter. The use of RSPS may result in reduced surface runoff losses, due to the increased wetted diameter and the reduced peak precipitation rate. WDEL for RSPS were statistically related to wind speed, although no significant differences were found between both types of RSPS or between the two nozzle elevations. According to the experimental results, reducing the nozzle elevation will not result in reduced WDEL, but will increase the chances for runoff., This research was funded by the CONSI+D of the Government of Aragón (Spain) through grants P08/96 and P028/2000.

In this work, the Loma de Quinto irrigation district, located in Zaragoza (Spain) was characterised, and water use (WU) was assessed. The study was performed to contribute to the diagnostic analysis phase of an incipient management improvement process in this sprinkler-irrigated district. The objectives of this first paper of the series include: (1) characterising the irrigation systems, soil types and crops; (2) evaluating irrigation performance through the relationship between on-farm WU and net irrigation requirements (NIR); (3) identifying factors affecting on-farm WU. In order to accomplish these objectives, statistical analyses of field data, district records on WU and farmers' interviews were performed. Technical deficiencies were detected in solid-sets, centre-pivots and linear-moves. A seasonal irrigation performance index (SIPI), defined as the percentage of NIR to seasonal water billing, was determined at each plot and for each of the three study years. The average inter-annual SIPI amounted to 127%, indicating that crops in the district were consistently water stressed. An analysis of the SIPI for the main crops in the district revealed that water stress was more intense in drought resistant and/or heavily subsidised crops (SIPI for sunflower was 142%). The average irrigation interval (12.3 days) and irrigation depth (44 mm) were too high for some of the soils in the district. Farmers adjusted the irrigation interval to meet the seasonal change in irrigation requirements. The irrigation depth was reduced in windy days. In two of the three study years, large plots used less water than small plots, at a rate of about -5 mm ha-1. The high cost of irrigation water in relation to crop revenues, the technical deficiencies of the irrigation systems, and the limitations imposed by climate and soils appeared to be major causes of local water management problems. In a companion paper, irrigation evaluations and simulations are presented, and irrigation schedules for optimal crop yield are proposed and evaluated via simulation. Author Keywords: Sprinkler irrigation; Irrigation performance; Water use; Farm management

In the first paper of this series, the Loma de Quinto Irrigation District (LQD) was characterised, and water use was assessed. In this work, the analysis of the LQD is completed with field irrigation evaluations, solid-set sprinkler irrigation simulations and irrigation scheduling for optimal crop yield. The results of the irrigation evaluations indicated that the average Christiansen coefficient of uniformity (CU) for solid-sets, centre-pivots and linear-moves was 68.0, 75.5, and 80.0%, respectively. In solid-sets CU was severely reduced by wind speed. However, in centre-pivots and linear-moves CU was higher in evaluations with wind speeds between 2 and 6 m s-1 than under calm conditions. The evaluation data set was used to validate a ballistic solid-set sprinkler irrigation simulation model. The performance variables used for model validation were CU and the potential application efficiency of the low quarter (PAElq). Both variables were adequately predicted in the range of the observed values. The model was used to extend the evaluation results to all the solid-set plots in the LQD. CU maps were produced for different wind speeds and operating pressures. These maps can be used to identify plots with low irrigation performance. The effect of irrigation scheduling on crop yield and net benefit was analysed using the CropWat simulation model. Simulations of the 1997 irrigation practices performed on a limited number of plots detected a 12% decrease in crop yield due to deficit irrigation and/or large irrigation intervals. The introduction of an optimal irrigation schedule (avoiding yield reductions) would imply increasing the alfalfa seasonal irrigation depth by 101 mm, and applying light, frequent irrigation events. Due to labour scarcity in the LQD, the implementation of the optimal schedule would require a high degree of irrigation automation, which is currently unavailable. Taking into consideration the value of the additional yield and the costs of the extra irrigation water depth and the automation devices, the resulting net benefit would be 50 ha-1. The purpose of this analysis of the LQD is to contribute to the diagnostic analysis phase of an incipient Management Improvement Program at the LQD. In order to complete this phase, an interdisciplinary committee will perform a study not just on irrigation but on a wide scope of irrigated agriculture in the LQD. Author Keywords: Sprinkler irrigation; Irrigation uniformity; Simulation model

Pags.- 4 Tabls.- 9 Figs. Available online 11 June 2014. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, The simulation of center-pivot performance has been the subject of research efforts since the 1960s. Center-pivot models frequently use empirical equations relating pressure and sprinkler radial application pattern. Individual, stationary water application patterns are overlapped and the resulting water application is mapped in the field. Such models use constant tower angular velocity, neglecting the effect of tower alignment. In this work the discontinuous tower movement has been experimentally characterized and modelled, and a complete model has been developed by using a ballistic model of the center-pivot sprinklers considering nozzle diameter, operating pressure and wind speed. A detailed kinetic analysis of a four-tower commercial center-pivot was performed. Each tower was monitored using a high precision GPS, recording tower positions at high frequency. The experimental center-pivot was equipped with fixed spray plate sprinklers (FSPS). Five experimental center-pivot irrigation events were evaluated using catch-cans. The analysis of tower location data permitted to conclude that two key variables (linear speed and switching angle) showed normal distribution patterns. The center-pivot model was validated with catch-can data. Finally, the simulation tool was used to assess the effect of variable tower alignment quality, center-pivot travel speed and wind conditions on irrigation performance. Comparisons were performed in terms of radial, circular and total irrigation uniformity. Results indicate that the observed tower dynamics had no measurable effect on irrigation uniformity. Tower alignment quality started to be relevant when the switching angle lag was equal to or larger than 2°. In the conditions of this analysis, wind speed showed a clear effect on uniformity. As wind speed increased, uniformity first decreased and then increased. Further research is required to generalize these results to other center-pivot sizes and designs (sprinkler packages)., This research was funded by the Ministry of Economy and Competitiveness of the Government of Spain through grant AGL2010-21681-C03-01.

Surface irrigation simulation models have seldom been used in engineering practise, and district modernisation is not an exception. Surface irrigation evaluations were performed in the Almudevar irrigation district to obtain the parameters required for surface irrigation modelling. The total district irrigated area was divided into 92 design units, for which a characteristic blocked-end border was defined. Simulation was used to establish the current irrigation performance in each design unit, and district performance contour maps were built. Irrigation performance was characterised using potential application efficiency, with an average of 54%, and irrigation time, averaging 6 h ha−1. Simulated potential application efficiency of the low quarter was similar to the seasonal irrigation performance index (an estimate of irrigation efficiency) presented in the companion paper. A set of seven modernisation scenarios was defined. Two strategies were identified to improve the potential application efficiency in the scenarios: increase the irrigation discharge into the current blocked-end borders and/or substitute the current system with a solid set sprinkler irrigation system. The performance of each scenario was estimated using irrigation models to determine efficiency, water conservation and irrigation time. The modernisation investment costs were estimated and compared to the performance of each scenario. The best results (potential application efficiency of 77%, reduced water allocation by 14.4 106 m3 year−1) were obtained by a combination of blocked-end irrigation with a discharge of 200 l s−1 and sprinkler irrigation in the areas where surface irrigation efficiency could not attain 50%. The investment cost for this scenario was 3932 Euro ha−1. More expensive scenarios did not guarantee better performance.

The analysis of water management in irrigated districts is highly relevant. The present work highlights the principal irrigation management problems of the irrigation district of Almudevar, a representative surface irrigation district located in the northeast of Spain. The predominant irrigation system is blocked-end borders. The study included three phases: (1) assessment of crop water requirements of the main crops of the study area; (2) characterisation of soil depth and soil water retention; and (3) analysis of the current irrigation practices based on the study of the 1994 water records of the district. The following irrigation management problems were identified: (1) the mean volume of water billed to the farmers was 43% higher than the net irrigation requirements; (2) the volume of water billed to the farmers were inversely related to the farm size; (3) few, widely spaced, large irrigation events; (4) large delay time in water delivery; and (5) in selected crops and/or areas, water billing was lower than the net irrigation requirements, indicating the presence of marginal areas or heavily subsidised crops. This research could be applied in other areas of traditional surface irrigation systems. The goal of this methodology is to diagnose the actual level of water management and to provide data for the modernisation of the irrigation district. In a companion paper, a decision support system for the modernisation of the district is presented.

39 Pags., 4 Tabls., 8 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, Irrigation scheduling results from the irrigator's integration of meteorological, environmental and crop information. In this paper, the irrigation scheduling patterns of a group of irrigators in the Candasnos Water Users Association (WUA), located in north-eastern Spain, were analysed. Scheduling sprinkler and drip irrigation in this WUA shows additional complications due to the sharing of a collective pressurized irrigation network and to the need to file water orders two days in advance of its foreseen use. The database created by a remote surveillance and control system was mined to obtain the time evolution of hydrant operation time during the 2004–2008 irrigation seasons. Records were selected for clearly identified crops and irrigation systems, and for verified water allocations. Hydrant operation showed a relationship with meteorology (precipitation, wind speed, relative humidity and air temperature), although this relationship was often not evident when hydrants were individually analysed. Statistical analyses were run to classify irrigator's scheduling practices, leading to the establishment of ten different groups. The adopted classification criteria included the average number of weekly irrigations, the SD of the number of weekly irrigations and the modal range of the irrigation starting time. The irrigation pattern was determined by the irrigator (56%), the irrigation system (33%), and the crop (11%). Only in a fraction of the cases (22%) the time change in the scheduling pattern responded to a clear time trend; in 39% of the cases, changes in time appeared random. Further, 45% of the irrigators used the same irrigation pattern in at least half of their hydrant-years, independently of the crop. Only 14% of the irrigators applied different irrigation scheduling patterns to different crops. Our results suggest that irrigators do not find value or do not have the capacity to develop irrigation patterns more consistent and adapted to the local environment, the crops and the irrigation systems., This research was funded by grants 2006 CSD2006-00067 and AGL2010-21681-C03-01. Thanks are due to the board and technicians of the Candasnos WUA of the Riegos del Alto Aragón irrigation project.

43 Pag., 7 Fig., 5 Tabl. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, Irrigation water use in private landscapes represents an increasing share of total water use in semiarid areas. In this work, 102 households located in the Montecanal neighbourhood (Zaragoza, Spain) were analysed. Research took advantage of the dual water supply network (separate indoor and irrigation water networks). The analysis was based on bi-monthly water billing records for the period 2005–2007. The total household landscape area (93 m2) and the area occupied by turf, trees and shrubs were derived from aerial photographs. A method based on reference evapotranspiration was used to estimate net landscape irrigation requirements. The total average water use was 0.80 m3 household−1 day−1, with irrigation water use amounting to 46% of the total water use. Average air temperature largely determined irrigation water use (the correlation coefficient was 0.958). Overirrigation was common in the three years of study, with the average irrigation water application (IWA) being much higher than the Net Irrigation Requirements (1359 and 555 mm, respectively). Only 34% of the households showed adequate irrigation, while 6% of the households underirrigated their landscape areas. In the rest of the households (60%), overirrigation was observed. Significant time correlations were found for IWA and for an adequacy index, suggesting that landowners applied their inadequate irrigation criteria in a consistent way. Local private landscape irrigation performance was found to be very poor, probably owing to low water cost and over-the-average household income., This research was funded by the Ebro Watershed Authority (Confederación Hidrográfica del Ebro) and by the National Research, Development and Innovation Plan of the Government of Spain (Plan Nacional de I + D + i) through grants AGL2007-66716-C03 and CSD2006-00067.

The final version is available at: http://www.sciencedirect.com/science/journal/03783774, Cultivation of paddy rice in semiarid areas of the world faces problems related to water scarcity. This paper aims at characterizing water use in a set of paddies located in the central Ebro basin of Spain using experimentation and computer simulation. A commercial field with six interconnected paddies, with a total area of 5.31 ha, was instrumented to measure discharge and water quality at the inflow and at the runoff outlet. The soil was classified as a Typic Calcixerept, and was characterised by a mild salinity (2.5 dS m 1) and an infiltration rate of 5.8 mm day-1. The evolution of flow depth at all paddies was recorded. Data from the 2002 rice growing season was elaborated using a mass balance approach to estimate the infiltration rate and the evolution of discharge between paddies. Seasonal crop evapotranspiration, estimated with the surface renewal method, was 731 mm (5.1 mm day-1), very similar to that of other summer cereals grown in the area, like corn. The irrigation input was 1,874 mm, deep percolation was 830 mm and surface runoff was 372 mm. Irrigation efficiency was estimated as 41%. The quality of surface runoff water was slightly degraded due to evapoconcentration and to the contact with the soil. During the period 2001-2003, the electrical conductivity of surface runoff water was 54% higher than that of irrigation water. However the runoff water was suitable for irrigation. A mechanistic mass balance model of inter-paddy water flow permitted to conclude that improvements in irrigation efficiency can not be easily obtained in the experimental conditions. Since deep percolation losses more than double surface runoff losses, a reduction in irrigation discharge would not have much room for efficiency improvement. Simulations also showed that rice irrigation performance was not negatively affected by the fluctuating inflow hydrograph. These hydrographs are typical of turnouts located at the tail end of tertiary irrigation ditches. In fact, these are the sites where rice has been historically cultivated in the study area, since local soils are often saline-sodic and can only grow paddy rice taking advantage of the low salinity of the irrigation water. The low infiltration rate characteristic of these saline-sodic soils (an experimental value of 3.2 mm day-1 was obtained) combined with a reduced irrigation discharge resulted in a simulated irrigation efficiency of 60%. Paddy rice irrigation efficiency can attain reasonable values in the local saline-sodic soils, where the infiltration rate is clearly smaller than the average daily rice evapotranspiration., This research was funded by the Plan Nacional de I+D+i of the Government of Spain, through grant AGL2000-1775. Olga Pérez Coveta received a scholarship from the Plan Nacional de Formación de Personal Investigador of the Government of Spain.

The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, In this paper, a contribution to the design of collective pressurized irrigation networks in solid-set sprinkler irrigated windy areas is presented. The methodology is based on guaranteeing minimum on-farm performance, using a historical hourly wind speed database and a ballistic solid-set irrigation simulation model. The proposed method was applied to the Montesnegros Irrigation District (central Ebro basin, Spain). The district irrigates an area of 3,493 ha using an on-demand schedule. The average wind speed in the area is 2,8 m s-1. An analysis of district water records showed that farmers often reduce water demand when the wind speed is high, but their irrigation decision making is limited by the capacity of the irrigation network and by the unpredictable character of local winds. Simulations were performed for eleven irrigation seasons, two triangular sprinkler spacings (18x18 and 18x15 m), and two sprinkler models. The percentage of monthly suitable time for irrigation was determined for four management strategies. The first one was based on a wind speed threshold (3 m s-1), while the other three were based on three levels (standard, relaxed and restrictive) of two irrigation performance parameters: the Christiansen Uniformity Coefficient (CU) and the Wind Drift and Evaporation Losses (WDEL). The thresholds for the standard strategy were CU ≥ 84% and WDEL ≤ 20%. The suitable time for the first strategy (56%) was always lower than for the standard and the relaxed strategies (with respective average values of 75 and 86%), and higher than for the restrictive strategy (30%). In order to design the collective network, the hydrant operating time was equalled to the suitable time for irrigation. The differences in the cost of the collective network plus the on-farm equipment were particularly relevant between the restrictive strategy and the other three. Differences in suitable operating time were clear between sprinkler spacings, and less evident between sprinkler models. The application of the proposed methodology may be limited by the availability of historical wind speed records and CU estimates for different combinations of sprinkler models, sprinkler spacings and wind speed., CICYT of the Government of Spain (grant AGL2004-06675-C03-03/AGR) Government of Aragón (grant PIP090/2005)

The definitive version is available at: http://ees.elsevier.com/agwat, Experiments were performed in the Ebro Valley of Spain to provide the basis for the calibration and validation of a ballistic simulation model of sprinkler irrigation. The experiments included evaluations of isolated sprinklers and solid-sets. Two different sprinklers, two principal nozzle diameters and three operating pressures were considered in the experiments, which also covered the usual range of wind speeds in the study area. Model calibration served the objectives of predicting the Christiansen Coefficient of Uniformity (CU) and the water application pattern. The resulting standard error of CU estimation was 3.09 %. Tables of simulated uniformity were produced for the two sprinklers using different nozzle diameters, sprinkler spacings, operating pressures and wind speeds. These tables can be used for design and management purposes, identifying options leading to adequate irrigation uniformity. A simple simulation software has been produced and disseminated to assist irrigation professionals and farmers in decision making., This research was funded by the CONSI+D of the Government of Aragón (Spain) through grant P028/2000 and by the Plan Nacional de I+D+I of the Government of Spain through grant AGL2004-06675-C03/AGR.

37 Pags.- 1 Tabl.- 7 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, Population increase and the improvement of living standards brought about by development will result in a sharp increase in food demand during the next decades. Most of this increase will be met by the products of irrigated agriculture. At the same time, the water input per unit irrigated area will have to be reduced in response to water scarcity and environmental concerns. Water productivity is projected to increase through gains in crop yield and reductions in irrigation water. In order to meet these projections, irrigation systems will have to be modernized and optimised. Water productivity can be defined in a number of ways, although it always represents the output of a given activity (in economic terms, if possible) divided by some expression of water input. Five expressions for this indicator were identified, using different approaches to water input. A hydrological analysis of water productivity poses a number of questions on the choice of the water input expression. In fact, when adopting a basin-wide perspective, irrigation return flows often can not be considered as net water losses. A number of irrigation modernization and optimization measures are discussed in the paper. Particular attention was paid to the improvement of irrigation management, which shows much better economic return than the improvement of the irrigation structures. The hydrological effects of these improvements may be deceiving, since they will be accompanied by larger crop evapotranspiration and even increased cropping intensity. As a consequence, less water will be available for alternative uses.

The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774 http://dx.doi.org/10.1016/j.agwat.2005.01.015, Wind drift and evaporation losses (WDEL) represent a relevant water sink in sprinkler irrigation, particularly in areas with strong winds and high evaporative demand. The objectives of this paper include: 1) Characterize WDEL under day and night operation conditions for solid-set and moving lateral configurations; 2) Propose adequate predictive equations; and 3) Prospect the effect of sprinkler irrigation on the meteorological variables and on the estimates of reference evapotranspiration. A total of 89 catch can irrigation evaluations were performed in both irrigation systems and under day and night conditions. Different predictive equations of WDEL were proposed for combinations of the two irrigation systems and the two operation times. The equations were selected based on their capability to explain and predict WDEL. Most equations use wind speed alone as an independent variable, although some use relative humidity or combinations of both variables plus air temperature. In the semi-arid meteorological conditions of Zaragoza (Spain), the average WDEL for the solid-set were 15.4 % and 8.5 % during day and night irrigations, respectively. For the experimental moving lateral, losses amounted to 9.8 % during the day and 5.0 % during the night. The effect of sprinkler irrigation on the meteorological variables was moderate, with small increases in relative humidity (3.9 %) and decreases in air temperature (0.5 ºC) during the irrigation event and a few minutes afterwards. Consequently, reference evapotranspiration, estimated by the Penman-Monteith method, decreased during the irrigation event by 0.023 mm h-1 on the average. This decrease represents 2.1 % of WDEL, suggesting that the WDEL do not significantly contribute to satisfy crop water requirements, and therefore constitute a consumptive water loss., This research was funded by the CONSI+D of the Government of Aragón (Spain) through grant P028/2000 and by the Plan Nacional de I+D+I of the government of Spain through grant AGL2004-06675-C03-03/AGR.

40 pag., 4 Tabl., 7 Fig. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, The surface Irrigated District V of the Bardenas Canal (Zaragoza, Spain) was evaluated, and alternatives were assessed to improve on-farm irrigation performance. Field work consisted of a soil survey and a campaign of irrigation evaluation. The results of the irrigation evaluations were extrapolated to the whole district using a hydrodynamic surface irrigation model. An average irrigation discharge of 152 L s−1 results in a relatively low irrigation time (2.8 h ha−1). Shallow soils, a limited conveyance network, and poor irrigation management practices determine that the application efficiency in the district is low, with an average of 49%. The district wide irrigation efficiency only reaches reasonable values when the system operates under water scarcity (49% in 2000 versus 66% in 2001). The simulation of surface irrigation indicated that the optimum irrigation time in the current situation is 1.7 h ha−1. The optimization of the irrigation time would lead to an average application efficiency of 76%. Improved irrigation management can therefore result in substantial water conservation in the district., This research was funded by the Plan Nacional de I+D of the Government of Spain, by the FEDER funds of the European Union through grant 2FD97-0547-C02, and by the CONSI+D of the Autonomous Government of Aragón (awarding a research scholarship to S. Lecina).

58 Pags.- 10 Tabls.- 6 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, Fallowing remains a feature of dryland cereal agriculture in some low rainfall areas of central and northern Spain. To complement the limited number of measurements of water stored during the fallow, we developed a physically based simulation model to estimate the effects of variations in rainfall, soil characteristics and surface conditions on water storage in the profile. Mean annual rainfall in the locations investigated varied from ca. 300–500 mm and the mean amount of water stored during the last year of a bare fallow ranged from 1–48 mm, depending on soil and climate. The standard deviations of these amounts, each based on 25 simulations, varied from 11–39 mm. Rainfall in the last 3 months of the fallow was the principal cause of this year to year variation in storage. Surface stoniness and crop residues decreased evaporation from the soil and increased storage: there was very little drainage. These findings are consistent with measured water storage in soils in this part of Spain, and other areas of the world with similar climates and agricultural practices. Based on barley yield/rainfall regressions for data from a dry area in the Ebro valley, we estimated that the annual yields from a crop–fallow system would be 15% greater than those from annual cropping. For fallowing to be economic, yields per crop would need to be about twice those obtained with annual cropping. There may be yield benefits from fallowing apart from those resulting from extra water storage in the soil. Unless such benefits can be demonstrated, fallowing would appear to be uneconomical in this area of Spain.

43 Pags.- 4 Tabls.- 11 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, Microtopography has long been recognized as one of the key variables in level-basin irrigation performance, although little effort has been devoted to establish its relevance. In this work, experimental data are used to quantify the influence of microtopography on irrigation performance. An irrigation evaluation was performed on a small level-basin (256 m2) LASER levelled to zero slope. Irrigation depth was gravimetrically measured and estimated at the 49 nodes of a regular network. Data from the irrigation evaluation and a two-dimensional flat-bed model were used to estimate irrigation depth. Irrigation times, soil surface elevation and distance to the inlet were estimated at the same nodes, and a correlation matrix was computed. Results showed that soil surface elevation was highly and significantly correlated with the times of advance (0.725∗∗∗), recession ( −0.815∗∗∗) and opportunity ( −0.852∗∗∗), and with the measured irrigation depth ( −0.583∗∗∗). Distribution uniformity using soil water measurements was 71.0%. Estimates from the irrigation evaluation and the two-dimensional model were 85.3% and 94.9%, respectively. The irrigation evaluation procedure could explain 30∗∗∗% of the measured variability in irrigation depth. A large part of the unexplained variance in measured irrigation depth seems to be due to the spatial variation of infiltration properties. Predictions by the two-dimensional model were not significantly related to the measured values. A simple method was devised to estimate microtopography-adjusted irrigation performance from the results of a flat bed model and the standard deviation of elevation. Microtopography can have an important effect on level-basin irrigation performance. Models not considering this variable may incur large errors when simulating irrigation performance.