Effects of travel speed and collector on evaluation of the water application uniformity of a center pivot irrigation system

Abstract

Water application uniformity is an important performance parameter when designing and operating an irrigation system. Performance tests of a center pivot irrigation system equipped with fixed and rotated spray plate sprinklers (FSPS and RSPS, respectively) were conducted at five travel speeds. The effects of travel speed, collector size, and setting height on water application uniformity were evaluated using Heermann and Hein's coefficient of uniformity (CUH). The CUH was 12.7% higher for the RSPS than the FSPS and decreased as the travel speed increased. Collector size and setting height affected CUH, and CUH was higher when the collector had a large opening cross-section compared to the collector with a small opening cross-section. CUH was higher when the collector with a low setting height compared to when it a high setting height for the FSPS. However, collector setting height had no effect on CUH for the RSPS. The weighted average water application depth (Dw) decreased as the travel speed increased. Collector size had no significant effect on Dw, but Dw with a low collector setting height was larger than the values with a high collector setting height. The water application rate increased as distance from the pivot point increased and was higher for the FSPS than the RSPS. The results will improve the selection of travel speed and collector when the water application uniformity of a center pivot irrigation system is evaluated.