Agriculture Reference
In-Depth Information
in the default system efficiency value. The approach makes provision for the
occurrence of nonbeneficial spray evaporation and wind-drift, in-field convey-
ance, filter and other minor losses.
• When an irrigation system is evaluated, the system efficiency value can be com-
pared with these default values, and possible significant water loss components
identified as areas for improvement. The approach is therefore more flexible
and easier to apply than the original efficiency framework where definitions
limited the applications.
It should always be kept in mind that a system's water-application effi ciency will
vary from irrigation event to irrigation event, as the climatic, soil and other infl uenc-
ing conditions are never exactly the same. Care should therefore be taken when ap-
plying the SE indicator as a benchmark, as it does not make provision for irrigation
management practices.
TABLE 3
New default system efficiency values [11].
Losses
New
default
system effi-
ciency (net
to gross
ratio)
(%)
Non-beneficial
spray evapo-
ration and
wind drift
(%)
In-field
convey-
ance
losses
(%)
Filter
and
minor
losses
(%)
Total
Losses
(%)
Irrigation system
Drip (surface and sub-
surface)
0
0
5
5
95
Microspray
10
0
5
15
85
Centre Pivot, Linear
move
8
0
2
10
90
Centre Pivot LEPA
3
0
2
5
95
Flood: Piped supply
0
3
2
5
95
Flood: Lined canal sup-
plied
0
5
2
7
93
Flood: Earth canal sup-
plied
0
12
2
14
86
Sprinkler permanent
8
0
2
10
90
Sprinkler movable
10
5
2
17
83
Traveling gun
15
5
2
22
78
It is recommended that system effi ciency be assessed in terms of the losses that
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