1.1 Irrigation Efficiencies

Irrigation Efficiency (Ea) is a term that is based on using a minimum amount of water and not wasting it. Irrigation efficiency is water use efficiency. A system might have a high uniformity of growth but be inefficient because of excessive run times and the high amount of water applied. Water moving below the root zone in soil or out the bottom of a container is an example of not being efficient. Uniformity is primarily related to the mechanical performance of the system in distributing the water. Efficiency and uniformity are related but different terms.

An efficient irrigation system has good uniformity when each square foot of area under the system receives the same amount of water. This is particularly important when the crop has a small foot print on the ground. Each nursery or greenhouse container has a small foot print and relies on the water that falls into the container (Figure 1.1a). Each separate container in a large growing bed has the same situation so overall crop growth uniformity depends on water application uniformity. A tree planted out in the landscape has roots that extend many feet in each direction so it can have some roots in wetter or drier areas and still gather enough water.


Sprinkler selection during the system design will influence uniformity. Selection factors include spray vs. single nozzle vs. multiple nozzle; sprinkler pressure vs. pressure variation; and sprinkler location and spacing.


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Figure 1.1a. Nursery containers require uniform water application to achieve uniform wetting of all individual containers.