4.2.2.2 Is the irrigation application uniform?

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Uniformity of application, or distribution uniformity refers to how evenly the irrigation water is applied across the pivot circle. With poor uniformity some parts will be either under or over-irrigated. Factors that can contribute to non-uniformity include:

excessive sprinkler spacing, incorrect nozzle operating pressure, or incorrect nozzle size;
nozzle height, angle and wear;
non-uniform machine movement, including step size and consistency and wheel slippage;
flow rate variations due to intermittent end-gun operation,
variation in pump performance, such as through wear,
end-gun uniformity, particularly under windy conditions; and
run-off from high average application rates, particularly at the outer end of large pivots.

Uniformity is measured by comparing the depth of water applied at various points within the pivot circle. Catch cans are used to measure application depths to calculate uniformity.
The measurement and calculation process is reasonably complex, and perhaps beyond what most farmers are prepared to do. However, measurement of the depth of application at a number of points with catch cans and comparison with what is supposed to be applied gives an indication.

For more information see: the DPI Agnote Centre Pivot Performance Check.

is the irrigation uniform?

Reference

Foley, J. (2005) "Centre Pivot and Lateral Move Machines" in Cotton Catchment Communities Cooperative Research Centre, Section 4.6 (external link).

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