An irrigation technology or practice can be measured in many ways. Two of the most commonly used terminology when it comes to measuring an irrigation systems performance is uniformity and efficiency. In irrigation quite often the terms uniformity and efficiency are used interchangeably; but, in reality, they each define a different situation. To be more exact, efficiency is the ratio between how much water the plant beneficially uses compared with how much water the irrigation system applies.
Percent efficiency = 100 x water used by the plant / water applied
Uniformity, on the other hand, relates to how evenly you apply water over an area. Equipment selection and the design of the irrigation system affect the uniformity of your irrigation system. This includes sprinkler types, nozzle size, pressure, pipe size, installation and system maintenance. Uniformity is generally measured as DU or distribution uniformity. To find DU one usually sets out catch cans and takes measurements. You then rank the catch-can readings from low to high. Take the average of the lowest 25 percent of the catch can readings. (For example, if you use 16 catch cans, take the average of the four lowest readings.) Divide the average lower quartile by the average of all the catch-can readings. Multiply the resulting decimal by 100 and express as a percentage.
Percent DU = Average catch in the low quartile x 100 / Average catch overall
System design and management are keys to efficient irrigation systems. This means to get optimum performance from your irrigation system, you must properly design, maintain, and manage it. If you don’t optimize any of these variables, system efficiency will be reduced.
