Determination of the Center-pivot Sprinkler Irrigation Uniformity Coefficient Applying the Ballistic Model

Water must be uniformly distributed over the whole farm field if a uniform growth of irrigated plants is desired. Therefore، achieving acceptable uniformity using a center pivot irrigation system is of utmost importance. This may be achieved by using an appropriate model to fine - tune the system by adjusting pressure، nozzle diameter، lateral spacing، revolution velocity، etc. Currently، suitable simulation models for fine- tuning the sprinkler irrigation are available. These models are useful tools for predicting operation parameters such as uniformity coefficient for various combinations of operation pressure and different meteorological conditions. The ballistic principle is the most common theory used in modeling water distribution uniformity in sprinkler irrigation systems. This principle and the necessary experimental and computational steps taken necessary for calibration and validation of the model for determination of sprinkler irrigation uniformity are presented in this paper. Experimental set-up for the determination of uniformity coefficient (UC) for different wind speeds included two operation pressures and two brands of sprinklers. The experiments were conducted on a farm adjacent to the Yaniq Village in the East province of Azarbayjan. Practical implications of the results indicated that relatively high UC may be achieved by the proper adjustment of pressure، the nozzle diameter and correct spacing of sprinklers.