Simplified method for estimating throw radius of rotating sprinklers on sloping land

Abstract

Radius of throw is an important index for assessing sprinkler performance. In the design of a sprinkler system, lateral and sprinkler spacings are determined on the basis of the radius of throw and the precipitation profile. Previous studies on sprinkler radius of throw focused on flat ground. Limited by experimental conditions, radius of throw on sloping land is difficult to measure. The calculation of throw radius is an important issue in the design of sprinkler irrigation systems on sloping land. In this study, a simplified method for calculating radius of throw for rotating sprinklers on sloping land is presented in the form of a model and was experimentally verified. The model is valid for land slopes below 0.20. The effects of sprinkler operating pressure, nozzle size and slope on radius of throw were analyzed using the model, and the results showed that operating pressure significantly affects radius of throw on sloping land, with a 95% confidence interval. Nozzle size and land slope were also found to be factors that affect the radius of throw. It is recommended that in the design of sprinkler irrigation systems on sloping land, the sprinkler should not be rotated through a whole circle when the slope exceeds 0.10, and the proper combination of pressure and nozzle size must be applied. These results are helpful to determine lateral spacing and sprinkler spacing for sprinkler system design on sloping lands.