HOW DOES YOUR SYSTEM PERFORM? By David Rowe - DPIRD
Knowing the performance of your irrigation system is vital for optimising scheduling and improving production efficiency. One of the best indicators of irrigation performance is uniformity, which is how evenly water is applied to the irrigated area. Systems with high uniformity can produce even-growing crops more efficiently. This is because systems with poor uniformity must operate for longer in order to apply the right amount of water to all parts of the crop. This uses more power and
creates ‘wet’ spots where water and nutrients move beyond the root zone and become unavailable to the plants.
Fixed overhead sprinklers
Performance data sheets for sprinklers indicate the level of uniformity to expect given a particular spacing, nozzle type and operating pressure. However, these indications do not account for real-world effects such as slope, wind and pressure variations which have a major impact on uniformity.
Above: Catch-cup test for impact sprinklers
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The Overflow - Autumn 2020
The best way to assess the performance of overhead sprinkler systems is with a catch-cup test. This involves placing measuring cups in a grid pattern within the irrigated area, running the irrigation system for a set amount of time - usually 15 or 20 minutes – and then recording the depth of water captured in each cup. Distribution uniformity (DU) is calculated by dividing the average of the lowest quarter of depths recorded
