Define distribution uniformity.

• A. The percentage that represents the portion of water applied by an irrigation system that benefits the intended plants.
• B. The percentage of water applied that reaches target plants.
• C. The total water used by the irrigation system.
• D. The average discharge rate of emitters

Answer: (A)

Distribution uniformity describes how evenly irrigation water is spread across the wetted area and, importantly, the portion of what you apply that actually benefits the crop. It’s about the share of applied water that reaches the plant root zones in a useful way, rather than being wasted to runoff, evaporation, or landing outside productive areas. When uniformity is high, most of the water contributes to the crop, so a larger percentage of applied water delivers value to the plants. If uniformity is low, water is distributed unevenly and a lot of it doesn’t reach the intended plants, reducing efficiency even if the total applied amount is the same. So this definition focuses on the effectiveness of the distribution across the field, not just the amount that reaches targets, the total water used, or the emitter flow rate.