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Sprinkler irrigation application uniformity is an important indicator for sprinkler irrigation system design, which can be expressed by the Christiansen uniformity coefficient (CU). The calculated accuracy of CU is closely related with catch‐can spacing and grid size. In theory, the smaller the catch‐can spacing and grid size are, the more accurate the calculation of CU is. However, smaller catch‐can spacing needs more labor in water distribution measurement, and smaller grid size needs more computer runtime to calculate CU. In order to recommend the proper catch‐can spacing and grid size, an experiment is carried out to obtain four different water distribution patterns, and data characteristics for water distribution with various catch‐can spacing and the effect of catch‐can spacing and grid size on CU are studied in the paper. The results show that CU is overestimated for the larger catch‐can spacing, especially when the distribution of water for the pattern is non‐uniformity. CU changes very little within a certain catch‐can spacing and grid size for all the four patterns. Considering the accuracy of CU calculation, labor cost, and the computational runtime, the recommended catch‐can spacing is 1.96 m for pattern I, 0.92 m for patterns III and IV, and the recommended grid size in the calculation of CU is 1.25, 1.0, and 0.5 m for patterns I, III, and IV, respectively. [ABSTRACT FROM AUTHOR]

In order to assess whole-field sprinkler irrigation uniformity, an experiment was conducted to obtain water distribution profiles at 23 different pressures for each of five different sprinklers: Nelson R33, Nelson R33LP, Nelson R33 with road guard, Nelson R33LP with road guard, and Rainbird Mini Paw/LG-3. A mathematical model was developed to account for pressure variation throughout a fixed sprinkler system on a 10-ha field and to evaluate sprinkler irrigation uniformity for the whole field using interpolated water distribution profiles from the experimental data. The relationships between irrigation application uniformity and sprinkler pressure, sprinkler spacing, pressure variation, sprinkler type, and field topography were studied using the model. The results show that the coefficient of uniformity, CU, decreases rapidly when the pressure is below the low end of the manufacturer-recommended range; however, CU changes very little with pressure within the manufacturer-recommended range. The system application uniformity, CU, is usually less when pressure variations at different locations in a field are considered, and a simple previously published equation to predict CU is shown to closely approximate the CU from a more stringent calculation method. It was found that the impact of pressure variation (within the tested ranges) on application uniformity is less than that of the sprinkler spacing. Also, the effect of field topography on sprinkler application uniformity is relatively small for the cases tested herein. [ABSTRACT FROM AUTHOR]

The coefficient of uniformity, CU, and the distribution uniformity, DU, are perhaps the two most common indicators of irrigation application uniformity, especially for pressurized irrigation methods. The magnitude of CU is usually greater than that of DU, but this is not the case for all data sets, as has been observed in practice by irrigation engineers and researchers. This paper describes the conditions under which CU > DU, and vice versa, proving that either situation can occur in practice. A comparison of some alternative measures of irrigation application uniformity is also compared using two data sets from agricultural sprinklers operating at different pressures. [ABSTRACT FROM AUTHOR]