Performance Evaluation of Irrigation Projects - Practices of Irrigation and On-farm Water Management - page 113

E a = (irrigation water available to the crop) × 100 / (water delivered to the field)

(4.1)

where

Irrigation water available to the crop root zone soil moisture after irrigation

- root zone soil moisture prior to irrigation
Water delivered to the field

=

= flow meter reading or nozzle flow rate

Kruse ( 1978 ) defined application efficiency as

E a = (average depth of water stored in the root zone) × 100 / (average depth applied)

(4.2)

For in-field evaluations where the depth of water applied is less than the root zone
moisture deficit prior to irrigation and runoff is not evident, the irrigation water
available to the crop can be assumed to be equal to the average depth of water
applied as measured at the soil surface (e.g., with catch cans in sprinkler system). In
these cases,

E a = [average depth applied (mm) × area (ha) / 10]

(4.3)

[water delivered to the field(m 3 )]

× 100 /

1m 3
Application efficiency is primarily affected by the management of the irrigation
and may vary significantly between irrigation events.
Attainable water application efficiencies of different irrigation systems under
normal condition are given in Table 4.1 .

Note :(1mm × 1 ha)/10 =

Table 4.1 Attainable application efficiencies under different irrigation systems (adapted from
Solomon, 1988 )

Type of irrigation system Attainable efficiency range

Surface irrigation
Border 75-85%

Basin 80-90%

Furrow 65-80

Sprinkler
Solid set or permanent 75-85%

Hand move or portable 75-85%

Center pivot & linear move 75-90%

Traveling gun 65-75%

Trickle irrigation
Point source emitters 80-90%

Line source 75-85%