Characterization of Rainfall under Center Pivot: Influence of Measuring Procedure

Abstract

A simulation model of rainfall under center pivots was used to elevate center-pivot testing procedures. The model calculates rainfall parameters such as weighted mean and uniformity coefficient for various scenarios including the case of a voluntarily disrupted machine. Observed variations in rainfall parameters suggested modifications to standard procedures in order to improve accuracy. Those modifications include staggering rain-gauge position on the two radii of measure and a uniformity coefficient derived from a coefficient of variation calculated on weighted values, theoretically more sensitive than existing approaches. Such a procedure has been proposed as an improvement over the draft international standard ISO/TC23/SC18/DIS 11545, “Agricultural Irrigation Equipment—CentrePivot and Moving Lateral Irrigation Machines Equipped with Sprayer or Sprinkler Nozzles—Determination of Uniformity of Water Distribution.”