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

Abstract

Numerous moving spray-plate center-pivot sprinklers are commercially available providing a range of drop size distributions and wetted diameters. A means to quantitatively compare sprinkler choices in regards to maximizing infiltration and minimizing runoff is currently lacking. The objective of this study was to develop a soil independent quantitative runoff potential index to facilitate selection of sprinklers for center-pivot sprinkler irrigation systems. Drop sizes, velocities and water application rates of numerous moving spray-plate sprinklers were measured in the laboratory over a range of flow rates and operating pressures. The proposed sprinkler runoff index is 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 provides a new and unique approach for evaluating moving spray-plate sprinklers in regards to runoff potential and provides an effective means for comparing sprinkler choices by identifying sprinklers with large drops and relatively small wetted diameters.