12869709 Irrigation depth and irrigation efficiency .ppt

Irrigation depth and irrigation efficiency

1. Irrigation Depths & Irrigation Irrigation Depths & Irrigation
EfficienciesEfficiencies
Shri M. U. Kale
Assistant Professor
Deptt. of Irrigation and
Drainage Engg.

2. Net Irrigation Requirement:
The net irrigation requirement is the depth of
irrigation water, exclusive of precipitation,
carry over soil moisture or groundwater
contribution or other gains in soil moisture i.e.
required consumptively for crop production.
It is the amount of irrigation water required to
bring the soil moisture level in the effective
root zone to field capacity.
Thus it is the difference between the field
capacity and soil moisture content in the soil
moisture content in the root zone before
starting irrigation.

3. This may be obtained by following
relationship:
Where, d=net amount of water to be applied during an
irrigation, cm
Mfci=field capacity moisture content in the ith layer of
the soil, per cent
Mbi=moisture content before irrigation in the ith layer of
the soil, per cent
Ai= bulk density of the soil in the ith layer
Di=depth of the ith layer of soil,cm, within the root
zone,and
n=number of soil layers in the root zone D.
1
( )
. .
100
n
fci bi
i i
i
M M
d A D




4. In drawing up the seasonal or monthly irrigation
requirement for a given crop or cropping
pattern the main variables composing the field
water balance include:
1.Crop water requirement as determined by
climate and crop characteristics,
2.Contribution from precipitation,
3.Groundwater , and
4.Carry over of soil water.

5. Gross irrigation requirement:
The total amount of water applied throughout
irrigation is termed as gross irrigation
requirement.
In other words, it is net irrigation requirement
plus losses in water application and other losses.
The gross irrigation requirement (IR) at the field
head, for instance can be determined as follows:

6. In which,
IR=seasonal gross irrigation requirment at
the field head, cm
D=net amount of water to be applied, cm
E
(application)
=water application efficiency, and
N=number of irrigation in season.
( )
1
n
application
d
IR
E


7. Irrigation frequency:
Irrigation frequency refers to number of days
between irrigations during periods without
rainfall.
It depends on the consumptive use rate of crop
and on the amount of available moisture in the
crop root zone.
It is the function of crop, soil and climate.
Sandy soils must be irrigated more often than
fine textured deep soil.

8. Irrigation period:
Irrigation period is the number of days that can
be allowed for applying one irrigation to a given
design area during the peak consumptive use
period of crop being irrigated.
It is the basis for irrigation system capacity and
equipment design.
The irrigation system must be so designed that
the irrigation period is not greater than the
irrigation frequency.

9. Irrigation efficiency:
Irrigation efficiency indicates how efficiently the
available water supply is being used on different
methods of evaluation.
Loss of irrigation water occurs in the conveyance
and distribution system, non-uniform distribution
of water over the field, percolation below crop
root zone and with sprinkler irrigation
evaporation from the spray and retention of
water on the foliage.
The losses can be held to a minimum by adequate
planning of the irrigation system, proper design
of the irrigation method, adequate land
preparation and efficient operation of the system.

10. 1. Water conveyance efficiency:
This term is used to measure the efficiency of
water conveyance system with the canal
network, water courses and field channels.
In which,
E
c=water conveyance efficiency, per cent
W
f=water delivered to the irrigated plot,
W
d=water diverted from the source
.100
f
c
d
W
E
W


11. 2. Water application efficiency:
A measure of how efficiently water is applied
to the field is the water application efficiency.
In which,
E
a=water application efficiency, per cent
W
s=water stored in the root zone of the plants
W
f
=water delivered to the field (at field supply
channel)
.100
Ws
Ea
Wf


12. 3. Water storage efficiency:
This concepts relates how completely the water
needed prior to irrigation has been stored in the
root zone during the irrigation. it is defined as
In which,
E
s=water storage efficiency, per cent
W
s=water stored in the root zone during irrigation
W
n
=water needed in the root zone prior to
irrigation.
.100
s
s
n
W
E
W


13. 4. Water distribution efficiency:
Not only the application of the right amount of
water to the field but also the uniform
distribution over the field is important.
Water distribution efficiency indicates the extent
to which water is uniformly distributed along the
run.
It is given as

14. In which,
E
d=water distribution efficiency, per cent
d=average of depth of water stored along the run
during the irrigation from d.
y=average numerical deviation
(1 ).100
y
Ed
d
 

15. 5.Water use efficiency:
The water utilization by the crop is generally
described in terms of water use efficiency
(kg/ha-cm or q/ha-cm).
It can be defined in following ways:
Crop water use efficiency:
It is the ratio of crop yield (Y) to the amount of
water depleted by the crop in the process of
evaporation (ET).
Water use efficiency
Y
ET


16. Field water use efficiency:
It is the ratio of (Y) to the total amount of water
used in the field (WR).
Field water use efficiency
Y
WR


17. 6. Project efficiency:
Project efficiency indicates the effective use
of irrigation water source in crop production.
It is the percentage of irrigation water that is
stored in the soil and is available for
consumptive use by crops.
7. Operational efficiency:
It is the ratio of the actual project efficiency
of an ideally designed and managed system
using the same irrigation method and
facilities.

18. 8. Economic efficiency:
Economic efficiency is the ratio of the total
production (net or gross profit) attained with the
operating irrigation system, compared to the
total production expected under ideal condition.
This parameter is a measure of the overall
efficiency, because it relates the final output to
input.

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