Modelling evaporation and drift losses in irrigation with medium size impact sprinklers under semi-arid conditions

A proper understanding of factors affecting evaporation and drift losses in sprinkle irrigation is important for developing water conservation strateg ies. For estimating drift and evaporation losses during the set sprinkler i rrigation event, several outdoor single-sprinkler and block irrigation test s have been conducted. Various sprinkler-nozzle-riser height combinations w ere used and the variation of evaporation and weather conditions (i.e. air temperature, relative humidity, vapour pressure deficit and wind speed) was measured during the test. In addition, several on-farm solid set evaluatio ns have been performed to evaluate evaporation and drift losses. Mathematic al modelling is complex, and several simplifications should be assumed. A s tatistical approach has been used with these data to estimate losses using a linear model. The losses were estimated as a function of the sprinkler ty pe, nozzle combination, vapour pressure deficit to the power of 0.5 and win d speed. Other climatic and operating factors did not have significant effe ct on the losses developed in this study. The model can be a useful tool to determine the irrigation timing as a function of environmental and operati onal conditions (e.g, working pressure, air temperature, relative humidity, etc.) in order to minimise evaporation and drift losses. (C) 2000 Elsevier Science B.V. All rights reserved.