Field Evaluation of Sprinkler Efficiency Under Arid Conditions

A proper understanding of factors affecting application efficiency of sprinkler irrigation is important for developing water conservation strategies in arid regions. Field experiments were conducted in Baotou, Inner Mongolia, during the growing season of spring wheat to evaluate the relative importance of the environmental factors affecting application efficiency and to estimate the seasonal application efficiency. The results showed that application efficiency for an individual irrigation event can exceed 0.85 under feasible environmental conditions in arid regions. Then, application efficiency was correlated to daily values of air temperature, relative humidity and wind velocity. Wind velocity was found to be the predominant factor affecting application efficiency, followed by the relative humidity, while air temperature had the least effect. Frequency distribution functions of daily wind velocity during irrigation season (from April to September) were analyzed for 11 years of data (1991～2001) to estimate the seasonal application efficiency. It was found that more than 90% of the days during irrigation season had a daily wind velocity not exceeding 3 m/s. Therefore, sprinkler irrigation applying water in the days with wind velocity not exceeding 3 m/s can usually meet crop irrigation requirements. Seasonal application efficiency of sprinkler irrigation was estimated based on the frequency distribution of wind velocity and the relationship between application efficiency and wind velocity proposed in this article. The results indicated that the seasonal application efficiency of sprinkler irrigation can be as high as 0.83 in arid regions.