Agriculture Reference
In-Depth Information
4.2.4.2 Field Water Use Indicators
Although field irrigation water use performance can be influenced by a large array of
factors, several measures together can provide a picture of how well irrigation water
is being used. Three main indices are commonly used to measure the application
system performance:
•
Application efficiency
•
Distribution uniformity
•
Storage efficiency
The above three irrigation performance measures should be used together to pro-
vide an adequate representation of the irrigation system. These are described in an
earlier section (Irrigation efficiencies).
It is generally difficult to design and manage irrigation systems in a manner that
maximizes all three of these indices simultaneously due to the conflicting nature
of each index. For example, high application efficiencies may be obtained through
significant under-irrigation producing a low storage efficiency, irrespective of the
uniformity of this application.
Other indicators are as follows:
Application Efficiency of Low Quarter
d
a,lq
D
E
a,lq
=
100
×
(4.20)
where
d
a,lq
=
average low quarter depth of water added to root zone storage (mm)
[
d
a,lq
≤
SWD]
D
average depth of water applied (mm)
E
a,lq
allows to take into consideration the nonuniformity of water application
when under-irrigation is practiced.
Both
E
a
and
E
a,lq
are applicable to surface, sprinkler, and trickle irrigation.
=
On-Farm Water Loss
It is the amount (depth) of water lost from the crop field per day. Specially, this
indicator is used for ponding water applications (e.g., in rice).
The amount of water loss from the plot (from ponding depth) due to seepage
and percolation per day or a certain period can be measured by installing vertical or
inclined gauges in the plot. In case of inclination, gauge should be inclined by a fixed
angle, and then the reading should be transformed to vertical depth by trigonometric
Search WWH ::
Custom Search