Irrigation System Designing - Practices of Irrigation and On-farm Water Management - page 99

• Spacings between sprinklers and laterals

• Design of main line and sublines

• Sprinkler line azimuth

• Pivot or ranger length

• System capacity for water supply

• Pump design

The most common design criteria for sprinkler laterals is that sprinkler discharge
should not vary by more than 10% between the points of highest and lowest pressure
in the system.

3.5.2 Theoretical Aspects in Sprinkler System

3.5.2.1 Water Distribution Pattern

In sprinkler system, the precipitation rate of water decreases from the center of
the irrigated circle to its edges (Fig. 3.7 ) . To overcome the problem, sprinklers are
spaced in such a way that their application rates overlap each other and cover the
nonuniformities.

6

Sprinkler location

5

4

3

2

1

0

-10 -5 0 5 10

Distance from sprinkler, m

Fig. 3.7 Schematic of application pattern of a sprinkler (after Zazueta and Miller, 2000 )

3.5.2.2 Factors to Be Considered in Sprinkler Design

For proper design of sprinkler, factors to be considered (in addition to spacing, noz-
zle size) are as follows: crop root zone depth, water use rate, wind, air temperature,
and humidity. Wind affects the distribution pattern of water by both wind speed and
direction.