Day and night wind drift and evaporation losses in sprinkler solid-sets and moving laterals

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 °C) 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.