The impact of certain engineering factors on the efficiency of water distribution in center pivot irrigation systems

ABSTRACT

This research evaluates dynamic (rotating) and fixed sprinklers at operating pressures of 6, 10, 15 and 20 psi (41.4, 68.9, 103.4 and 137.9 kPa) and ground clearances of 1.0, 1.5 and 1.8 m in El-Farafra, Egypt. The combined effects of pressure, clearance and sprinkler type on hydraulic performance and distribution uniformity were examined for a center-pivot system. Increasing pressure and clearance reduced the application rate across the tested sprinkler mechanisms. This was attributed to greater throw distance and longer droplet travel time to the soil surface. Dynamic sprinklers nevertheless produced more stable and uniform distribution than fixed sprinklers. Once pressure exceeded about 10 psi (68.9 kPa), dynamic-sprinkler uniformity became largely independent of nozzle height, while overlap between adjacent sprinklers continued to improve. Fixed sprinklers were more sensitive to pressure and clearance: at low pressure or greater clearance, uniformity and overlap deteriorated markedly. They generally gave higher instantaneous discharge, but their performance was less consistent. Overall, dynamic sprinklers performed better over a wider range of conditions. Given the strong winds, high evaporation and sandy soils of El-Farafra, a dynamic sprinkler operated at 10 psi (68.9 kPa) with 1.0 m ground clearance was the most efficient configuration.