What is the best method to determine distribution uniformity?

• A. Visual inspection of spray patterns
• B. Soil moisture sensors
• C. Measuring total system flow
• D. Conduct a catch can test

Answer: (D)

Assessing distribution uniformity requires data on how evenly water lands across the area. The most reliable method is a catch can test, where several calibrated containers are placed at grid points under the irrigation pattern and the system runs for a set time. After irrigation, you measure how much water is in each can and calculate distribution uniformity, typically by comparing the lowest quarter of readings to the overall mean. This method directly captures how water is applied across the entire area, accounting for variations due to nozzle type, spacing, pressure, and wind.

Visual inspection can hint at issues but doesn’t quantify how evenly water is distributed. Soil moisture sensors reveal soil water status at specific locations and times, not the actual distribution pattern during an irrigation event. Measuring total system flow tells you the total volume delivered, but not how that water was spread across the field.