What does distribution uniformity (DU) indicate in an irrigation system, and what DU value is typically desirable?

• A. DU indicates irrigation pump pressure
• B. DU measures how evenly water is distributed; aim for DU around 0.7 or higher
• C. DU indicates soil moisture content
• D. DU measures precipitation rate

Answer: (B)

Distribution uniformity is all about how evenly water is spread across the area being irrigated. It’s evaluated by measuring the depth of water at many points under the spray pattern (often with catch cans) and comparing the driest portions to the overall average. The idea is to ensure there aren’t dry patches or overly wet spots.

In practice, a DU value around 0.7 or higher is desirable. Higher DU means more uniform application and more efficient use of water, while lower values indicate uneven watering with wasted water on dry spots and overwatering elsewhere. This concept isn’t about pump pressure, soil moisture directly, or the amount of rain itself, but about how consistently the irrigation system delivers water across the area.