Agriculture Reference
In-Depth Information
Average Application Depth
The average application depth is the average amount applied throughout the field. It
can be computed as
V
A
d
av
=
(3.27)
where
d
av
is the average application depth (m),
V
is the volume pumped (m
3
), and
A
is the application area (m
2
).
3.5.3 Sprinkler Design
3.5.3.1 Considerations in Sprinkler Design
•
Main line capacity should be based on the water demand of the target crop consid-
ering peak use rate, minimum irrigation interval, and minimum operating hours
per day.
•
Application rate should not exceed soil intake rate.
•
The minimum design application rate should meet the maximum total daily wet
soil evaporation rate (for deficit irrigation plan, it will be different).
•
When determining capacity requirements, allowance should be made for reason-
able water losses during application (i.e., should consider application efficiency).
•
Maximum spacing of sprinklers should not be greater than 75%, and no closer
than 50% of wetted diameter listed in manufacturer's performance tables.
•
Riser pipes used in lateral lines should be high enough to minimize interference
with the distribution pattern.
•
The velocity and direction of prevailing winds and the timing of occurrence
should be considered when planning a sprinkler system.
•
Coefficient of uniformity (CU) data or distribution uniformity (DU) should be
used in selecting sprinkler spacing, nozzle size, and operating pressure.
3.5.3.2 Design Principles
•
Estimate application rate based on planned crop(s)/cropping patterns, atmo-
spheric water demand, and soil intake rate.
•
Draw a layout.
•
Optimize sprinkler spacing (between sprinklers and laterals), nozzle size, and
operating pressure that provide the design application rate and distribution
pattern.
•
Design sub-mains, main lines, and supply lines such that required water quantities
can be conveyed to all operating lateral lines at required pressures.
•
Design pump and power units such that they are adequate to efficiently operate
the sprinkler system at design capacity and total dynamic head.
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