Em4885 irrigation management practices to protect ground water

4 CHAPTER
Description
Sprinkle systems require proper overlapping of spray patterns from adjacent sprinklers for
good distribution uniformity. A correct overlap is the result of a correct combination of
sprinkler spacing, operating pressure, sprinkler head, and nozzle size. Manufacturers will
make recommendations concerning their products. Experienced irrigation engineers/
specialists will combine these recommendations with experience with local conditions to
design efficient sprinkle systems.
There are two dimensions to the sprinkler spacing with hand-line and side-roll sprinkle
systems, the spacing down the lateral and the move spacing. With center pivots and linear
moving sprinkle machines there is theoretically only one dimension, the spacing along
the pipeline.
IP 2.03.02 - Have a Competent and Experienced Irrigation Engineer/Specialist
Check Field Layouts for Flow Uniformity - Use Flow Control Nozzles, Pressure
Regulators as Necessary
Objective
Minimize the difference in flow from sprinkler to sprinkler.
Description
Flow uniformity means that the same amount of water is flowing from each sprinkler head.
It is the result of good pressure uniformity and good device uniformity. Assuming that the
same sprinkler head, nozzle, and nozzle type are used at each location, and assuming that
they are in good condition (device uniformity), flow uniformity is a matter maintaining of
a certain pressure uniformity. That is, the water pressure in the system should be nearly the
same at all points.
It is practically and economically impossible to design, install, and maintain a system at
100% pressure uniformity. However, competent engineers/specialists can design a system
where the pressure at each sprinkler will not vary beyond reasonable limits. Commonly
desired pressure differences are less than 15-20%. Pressure regulators or flow control
nozzles may be required in situations involving extreme elevation changes or long
pipeline runs.
With some center pivot designs different sprinklers will be specified for different flows
depending on their position on the span. In other design types, only the spacing of the
sprinklers is changed.
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