Overhead Irrigation

Measure overhead irrigation water distribution uniformity close to pump and far away from pump for irrigation systems that are infrastructurally different (i.e. different nozzle types, different emitter spacing, or different operating pressures).
The distribution uniformity of an overhead irrigation system is determined by measuring the amount of water in cups or collection containers distributed throughout the irrigated area. Place a minimum of 16 cups about 4 feet apart within the irrigated area. More cups can be used but cup number must be multiple of 4. Marbles or weights can be placed in each cup to prevent blow over. Operate the irrigation system with all zones operating as usual. Record the time irrigation system operates. The depth of water may be measured directly in straight-sided cups; however, the volume must be measured for cups with tapered sides. Measure the volume or depth depending on type of cup and make note of location for each measurement. Locations may be referred to later for an assessment of low uniformity.
Calculate the Distribution Uniformity (DU) by dividing the average of the lowest one forth of the measurements by the overall average. DU should be greater than 80 percent. Low DU could be due to nozzle clogging, low pressure, high pressure, damaged water pipes, or improper nozzle rotation.