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

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A field experiment was performed to study the effect of the space and time variability of water application on solid set sprinkler irrigated corn yield. A solid set sprinkler irrigation setup -typical of the new irrigation developments in the Ebro basin of Spain -was considered. Analyses were performed to (1) study the variability of the water application depth in each irrigation event and in the seasonal irrigation, and (2) relate the spatial variability in crop yield with the variability of the applied irrigation and with the soil physical properties. The results of this research showed that a significant portion of the Christiansen coefficient of uniformity (CU) variability, wind drift and evaporation losses were explained by the wind speed alone. The seasonal irrigation uniformity (CU of 88 %) was higher than the average uniformity of the individual irrigation events (CU of 80 %). No evidence has been found proving that the

7The effect of reduced corn evapotranspiration (ET) during solid-set sprinkler 8 irrigation on application efficiency was analysed on two subplots. During each 9 irrigation event, one subplot was irrigated (moist treatment) while the other was not 10 (dry treatment). ET (weighing lysimeter) and transpiration (heat balance method) 11 rates were determined at each subplot before, during and after the irrigations. Zaragoza, Spain. E-mail: miriampuig81@hotmail.com 2 evaporation losses (SEL n ) were 14.4 to 17.5 % of the applied water. During night 1 time irrigations, changes in ET and transpiration were almost negligible, and SEL n 2 were slightly greater than WDEL g (9.5 % and 8.1 %, respectively, of applied water). 3 SEL n was mainly function of wind speed. Reduced ET and transpiration during 4 daytime irrigations moderately increased solid-set sprinkler application efficiency. 5

8Irrigation performance assessments are required for hydrological planning and as a first step 9 to improve water management. The objective of this work was to assess seasonal on-farm 10 irrigation performance in the Ebro basin of Spain (0.8 million hectares of irrigated land). The 11 study was designed to address the differences between crops and irrigation systems using 12 irrigation district data. Information was only available in districts located in large irrigation 13 projects, accounting for 58 % of the irrigated area in the basin. A total of 1,617 records of plot 14 water application (covering 10,475 ha) were obtained in the basin. Average net irrigation 15 requirements (IR n ) ranged from 2,683 m 1.16 and 0.65, respectively. Technical and economic water productivities were determined for 22

A comparison between experimental and simulated data, considering the Priestley and Taylor (PT) and Penman-Monteith (PM) Reference-Evapotranspiration (ET) 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 ET 0 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 ET 0 values were significantly lower than PM ET 0 calculations. Furthermore, simulated actual evapotranspirations considering the PT approach (PT-ET c) were lower than those found in the simulations that consider the PM approach (PM-ET c). Correspondingly, simulated drainage flux and soil water contents were higher when the PT ET 0 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 ET 0 calculation approaches. Mean and median differences between actual and simulated maize water-use were not statistically different from zero for both considered ET 0 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-ET c rather than PT-ET c 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.

During a sprinkler irrigation event some water is lost due to wind drift and evaporation (WDEL). Aft er the irrigation event, plant-intercepted water is lost due to evaporation. Th e water lost causes microclimatic changes which could result in positive or negative plant physiological changes. We studied the microclimatic and physiological changes on two fi elds grown with maize (Zea mays L.) irrigated with a solid-set sprinkler system. Th e temperature and vapor pressure defi cit (VPD) of the air were measured at the crop canopy level and above and below the canopy. Changes in maize canopy temperature, transpiration, and leaf water potential (LWP) were determined. Sprinkler irrigation during daytime strongly modifi ed the microclimate where plants grow during the irrigation time and for a short period aft er the irrigation event fi nished. Daytime irrigation decreased air temperature by 3.3 to 4.4°C and VPD by 1.0 to 1.2 kPa at 0.5 m below the crop canopy height. Th e decrease was lower as the measurement height increased. Microclimatic changes during nighttime irrigation were minimal. Daytime irrigation reduced maize canopy temperature by 4 to 6°C and plant transpiration by 58%, and increased LWP from -1.2 and -1.4 MPa to -0.54 MPa. Transpiration reduction must be considered positive because it supposes a reduction of WDEL. Th e decrease in maize canopy temperature could be positive or negative, but the increase in LWP is a positive eff ect.