Effect of Collector Size on Center Pivot Water Depth Catch

Abstract

Abstract. The ASABE standard on uniformity testing of a center pivot system contains specifications on the collector size to measure the applied water depth. The standard was developed before many of the current sprinkler application devices were developed. A study was conducted to compare the catch depths of five collector sizes (opening diameters of 5.5, 10, 14.8, 20, and 27.4 cm, referenced as C2, C4, C6, C8, and C10) for three types of sprinkler application devices: spinning plate, fixed plate, and wobbling plate sprinkler systems using four 5x5 Latin squares. Each collector’s water depth was measured and statistically analyzed. Two analysis of variance (ANOVA) tests of the collector size effect were reported. Past experimental results were also compared to this experiment’s results, which generally reaffirms the difficulty of consistently measuring irrigation application depth within the practical range of collector sizes. Based on sprinkler application devices, fixed plate tends to have a more consistent depth caught compared to wobbling plate and spinning plate. If the ideal collector size selection was based on minimum variability of depth measurements, then either C6 or C4 collectors could be used. This study showed that within the range of sizes used, collector size does not substantially affect measurement of application depths for center pivot sprinkler systems. Despite the challenging task, measurement is probably within 5% if an appropriate number of collectors are used. Keywords: Catch can collector size, Center pivot irrigation, Sprinkler packages, Uniformity.