What does Distribution Uniformity measure in an irrigation system?

• A. The total water applied over the entire area
• B. The uniformity of irrigation water over an area
• C. The number of emitters per zone
• D. The water pressure at the pump

Answer: (B)

Distribution Uniformity measures how evenly irrigation water is spread across the irrigated area during a cycle. It focuses on the variability of water depth from one part of the area to another. A high value means the driest parts receive nearly the same water as the average, resulting in uniform soil moisture and healthier plant growth. A low value indicates some areas are under-watered while others may receive more than enough, leading to stress and inefficiency. This metric is determined by comparing the water depth in the driest portion of the field (often the lowest quarter) to the overall average water depth, and expressing the result as a percentage. It’s about distribution quality, not the total amount of water applied, the number of emitters, or the pump pressure alone.