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Moving Spray-Plate Center-Pivot Sprinkler Rating Index for Assessing Runoff Potential

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Transactions of the ASABE. 59(1): 225-237. (doi: 10.13031/trans.59.11162) @2016
Authors:   Bradley A. King
Keywords:   Center-pivot, Infiltration, Kinetic energy, Runoff, Sprinkler, Sprinkler irrigation.

Abstract. Numerous moving spray-plate center-pivot sprinklers are commercially available, providing a range of droplet size distributions and wetted diameters. Currently lacking is a means to quantitatively compare sprinkler choices with regard to maximizing infiltration and minimizing runoff. The objective of this study was to develop a soil-independent, quantitative potential runoff index to facilitate selection of sprinklers for center-pivot sprinkler irrigation systems. Droplet sizes, droplet velocities, and water application rates of numerous moving spray-plate sprinklers were measured in the laboratory throughout a range of flow rates and operating pressures. The proposed sprinkler runoff index was based on application rates of kinetic energy and water computed by overlapping specific power and water application profiles of sprinklers equally spaced 3 m along a center-pivot lateral. Results show that substantial differences in runoff potential exist between sprinkler choices, and several sprinklers can have similar runoff potential index values. In some cases, equivalent potential runoff index values were obtained with compensating differences in specific power and application rate. The proposed sprinkler runoff index, in which larger index values reveal a lower potential for runoff, provides a new and unique approach for evaluating moving spray-plate sprinklers with regard to potential runoff. The runoff index provides an effective means for comparing sprinkler choices by identifying sprinklers with large droplets and relatively small wetted diameters.

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