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 strategies. For estimating drift and evaporation losses during the set sprinkler irrigation event, several outdoor single-sprinkler and block irrigation tests have been conducted. Various sprinkler±nozzle±riser height combinations were used and the variation of evaporation and weather conditions (i.e. air temperature, relative humidity, vapour pressure de®cit and wind speed) was measured during the test. In addition, several on-farm solid set evaluations have been performed to evaluate evaporation and drift losses. Mathematical modelling is complex, and several simpli®cations should be assumed. A statistical approach has been used with these data to estimate losses using a linear model. The losses were estimated as a function of the sprinkler type, nozzle combination, vapour pressure de®cit to the power of 0.5 and wind speed. Other climatic and operating factors did not have signi®cant effect 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 operational conditions (e.g. working pressure, air temperature, relative humidity, etc.) in order to minimise evaporation and drift losses. # 2000 Elsevier Science B.V. All rights reserved.