Irrigation system design is based on spacing sprinklers from head to head. That is, the sprinklers’ radius of throw dictates the spacing. However, this is a rule of thumb and doesn’t take into account the actual profile of the sprinkler. The profile is affected by four variables:
1. The size of the nozzle
2. The shape or design of the nozzle
3. The operating pressure
4. The rotation speed of the sprinkler
If one of these variables is changed, the profile and the overall uniformity will be comprised because the nozzle size and the operating pressure are interrelated. For instance, if a sprinkler operates below operating pressure, it will produce a fire hose effect. If it operates above the recommended pressure, the pressure will begin to atomize the water jet and destroy the desired profile. A damaged/worn-out sprinkler rotor and/or nozzle will also have a dramatic impact on uniformity.
Therefore, it’s important to note that when repairing a broken sprinkler, one must ensure that the proper nozzle is used, and that there is consistent rotation time and pressure between each sprinkler. If not, the overall irrigation pattern will change and one may experience wet or dry spots that were not previously a problem
Now, to achieve good uniformity, not only does the nozzle profile need to be assessed, it is important to select a nozzle/spacing combination that is forgiving to small changes in the field. And in realty, placing sprinklers in the field is an art due to obstacles such as bunkers, trees and irregular shaped greens.
So, how does a Superintendent select a nozzle that will give him the ultimate uniformity on each area throughout the golf course?
First, a Superintendent should hire an irrigation consultant, who has a good understanding the turfgrass growing environment. An irrigation consultant needs to understand how important it is to strategically position sprinklers which address: specific site conditions along with soil – water plant relationships
Second, an irrigation consultant should have a good understanding of SPACE Pro (The Sprinkler Pattern Analysis and Coverage Evaluation) developed by the Centre for Irrigation Technology. SPACE Pro is not intended as a designed system, but an objective measure of important variables that should be considered when purchasing or changing a sprinkler system and obtaining optimal sprinkler uniformity.
Space Pro allows the user to mix and match a variety of nozzle/spacing combinations to determine the best uniformity value for a particular area.
Now, with that said, a sprinkler head must be level and free from any obstruction! If not, no matter how much planning you do to select the right nozzle/spacing combination, you’ll never achieve optimal uniformity
In conclusion, matching a sprinkler nozzle with sprinkler spacing isn’t as simple as head to head spacing. The profile of the nozzle must be taken into account to accommodate for the specific site conditions, be forgiving to small changes, and be continually monitored to ensure successful irrigation
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