CE8603 Irrigation Engineering Unit 2 Notes

1. UNIT-2
IRRIGATION METHODS
A.Leema Margret,
Assistant Professor (Civil),
Ramco Institute of
Technology, Rajapalayam

2. Syllabus
IRRIGATION METHODS
Tank irrigation – Well irrigation – Irrigation methods: Surface and
Sub-Surface and Micro Irrigation – design of drip and sprinkler
irrigation – ridge and furrow irrigation-Irrigation scheduling –
Water distribution system- Irrigation efficiencies.

3. METHODS OF IRRIGATION

24. Contour Farming
• This method is adopted in hilly areas Where the land has
steep slopes.
• Land is divided into series of horizontal strips aligned along
the contours of land known as terraces or benches.
• Small bunds are provided at the end of each terrace to hold
water upto the required depth.

26. MICRO IRRIGATION METHOD

27. MICRO IRRIGATION METHOD
 Micro irrigation methods are precision irrigation methods of
irrigation with very high irrigation water efficiency.
 In many parts of the country there is decline of irrigation
water and conventional methods are having low water use
efficiency.
 To surmount the problem, micro irrigation methods has
recently been introduced in Indian agriculture.

28.  These methods save a substantial amount of water and
helps increasing crop productivity particularly valuable
cash crops like vegetables.
 The research results have confirmed a substantial saving
of water ranging between 40 to 80% and there are
reports of two times yield increase for different crops by
using micro irrigation.

29. Advantages of Micro Irrigation
(a) Water saving, possibility of using saline water.
(b) Efficient and economic use of fertilizers.
(c) Easy installation, flexibility in operation.
(d) Suitable to all types of land terrain also suitable to waste lands.
(e) Enhanced plant growth and yield and uniform and better quality
of produce.
(f) Less weed growth.
(g) Labour saving.
(h) No soil erosion, saves land as no bunds, etc. are required.
(i) Minimum diseases and pest infestation.

30. SPRINKLER IRRIGATION

32. This method is useful when,
o Land topography is irregular
o Land slopes are excessive
o Land cannot be prepared for surface methods
o Soil is erosive
o Soil is excessively permeable or highly impermeable
o Water is available with difficulty and scarce
o Water table is high

34. Components of
Sprinkler Irrigation System

35. Components of Sprinkler Irrigation System
(a) A pump unit
(b) Mainline and sometimes sub-mainlines
(c) Laterals
(d) Risers
(e) Sprinklers
(f) Fertilizer injector or Fertigator

36. • A pump unit usually a centrifugal pump which takes water
from a well/water source and provides adequate pressure
for delivery into the pipe system.
• The mainlines and sub-mainlines are pipes which deliver
water from the pump to the laterals.
• The laterals delivers water from the mainlines usually
movable.
• The risers deliver water from lateral line to the sprinkler.
The length of riser depends on the crop, although minimum
value of 30cm is recommended to assume a good
distribution pattern.
Components of Sprinkler Irrigation System

37. • Sprinklers are used to spray the pressurized water
through an orifice and rotates to distribute water onto
the field.
• Fertilizer injector is attached to the sprinkler system
to inject chemicals or pesticides into irrigation
mainline and applied to the land.
• In addition to that valves are fixed to control the flow
of water and flow meters, pressure gauges are
provided to monitor system performance.
Components of Sprinkler Irrigation System

38. Classification or types of Sprinkler Systems
1. Classification based on arrangement of spraying:
(a) Perforated pipes sprinkler system.
(b) Fixed Nozzle sprinkler system.
(c) Rotating head or revolving sprinkler system.
2. Classification based on portability:
(a) Permanent system.
(b) Semi permanent system.
(c) Fully Portable system.

39. (a) Perforated pipes sprinkler system

40. This method consists of drilled holes or nozzles along their
length through which water is sprayed under pressure. This
system is usually designed for relatively low pressure (1 kg/cm2)

41. (b) Fixed Nozzle sprinkler system

42. (c) Rotating head or revolving sprinkler system.

43.  Small size nozzles are placed on riser pipes fixed at
uniform intervals along the length of the lateral pipe and
the lateral pipes are usually laid on the ground surface.
 They may also be mounted on posts above the crop
height and rotated through 90degree , to irrigate a
rectangular strip. In rotating type sprinklers, the most
common device to rotate the sprinkler heads is with a
small hammer activated by the thrust of water striking
against a vane connected to it.

45. Formula to determine discharge, spread and
capacity of sprinkler system
1. Sprinkler Discharge

47. 2. Spread of Sprinkler

48. 3. Capacity of Sprinkler System
Where,
Q = Discharge capacity of the pump, liter/sec,
A = Area to be irrigated, hectares,
d = Net depth of water application, cm,
F = Number of days allowed for the completion of
one irrigation,
H = Number of actual operation hours of the pump per day,
and
E = Water Application Efficiency in %

49. Advantages of Sprinkler Irrigation

50. Disadvantages of Sprinkler Irrigation
• High initial cost
• Uneven water distribution due to high winds
• Evaporation loss when operating under high temperatures
• High water pressure required in sprinkler (>2.5kg/cm2 )
• Technical personnel for its operation and maintenance is required
• Clean water is needed to avoid clogging of nozzles
• It is not adopted in places where plenty of cheap water is available
as surface methods are more useful and less costly
• Pipe system laid on the soil surface may interfere with farm
operations and movement of men and animals.

51. DRIP IRRIGATION

52. DRIP IRRIGATION
 Drip irrigation, also known as trickle irrigation is an irrigation method
which minimizes the use of water and fertilizer by allowing water to
drip slowly and directly applied to the root zone of the plants through
a network of heads, mains, sub-mains, laterals and drip nozzles or
emitters.
 It is becoming popular for row crop irrigation.
 This system is used in place of water scarcity as it minimizes
conventional losses such as deep percolation, evaporation and run-
off.
 This method of drip irrigation was first introduced in Israel, but is now
practised in many countries of the world.

54. Components of Drip Irrigation System
• Pump Unit or Pressurised water source
• Control Head (Gate valve, Pressure control
valve, Filter, Fertilizer tank)
• Mains and Submain Lines
• Laterals or Trickle lines
• Drippers or Emitters

55. DRIP IRRIGATION

57. • Pump Unit - A Pump to lift water so as to produce a desired
pressure, for ensuring proper flow of water through the system.
• Control Head - The lifted irrigation water through a fertilizer
tank, so as to mix the fertilizer directly in the irrigation water, and
then through a filter, so as to remove the suspended particles from
the water, to avoid clogging of drip nozzles.
• Mains and Submains – Specially designed small sized pipes,
made of flexible material like black PVC. These are generally
buried or laid on the ground.
Components of Drip Irrigation System

58. • Laterals – very small sized (1 to 1.25 cm dia) and usually upto
50m long specially designed black PVC pipes, taking off from
the mains or sub-mains.
• Drippers – drippers or emitters are fixed on laterals, at regular
interval of about 0.5 to 1 m and discharging water at very small
rates of the order of 2 to 10 liters per hour.

59. Advantages
1. Less requirement of
irrigation water (saves 40 to
70 % water compare to
conventional methods)
2. Water logging avoided
3. High yield
4. Cultivation of cash crops
5. No over-irrigation
6. Weed control
7. Nutrients preservation
8. Effective pest control
9. Reduced labour cost
10. No soil Erosion
11. Suitability for saline soils
12.Suitable for any
topography

60. Disadvantages
1. Initial setup cost of drip irrigation system is very high.
2. Danger of blockade of nozzles due to improper filtration.
3. Change in spacing of nozzles.
4. Requires high skill for installation and maintenance.
5. Flushing of tubes is required periodically.
6. Direct sunlight reduces the lifespan of the tubes used for
supplying water.
7. Pipe network can be destroyed by pests.

61. Performance
Indicator
Conventional Irrigation
Methods
Drip Irrigation
Water saving Waste lot of water.
Losses occur due to
percolation, runoff and
evaporation
40-70% of water can be
saved over
conventional irrigation
methods.
Runoff and deep
percolation losses are nil or
negligible.
Water use
efficiency
30-50%, because losses
are very high
80-95%

62. Saving in
labour
Labour engaged per
irrigation is higher than
drip
Labour required only for
operation and periodic
maintenance of the system
Weed
infestation
Weed infestation is very
high
Less wetting of soil, weed
infestation is very less or
almost nil.
Use of saline
water
Concentration of salts
increases and adversely
affects the plant growth.
Saline water cannot be
used for irrigation
Frequent irrigation keeps
the salt concentration
within root zone below
harmful level
Diseases and
pest
problems
High Relatively less because of
less atmospheric humidity

63. Suitability in
different soil
Type
Deep percolation is more in light
soil and with limited soil depths.
Runoff loss is more in heavy
soils
Suitable for all soil types as flow
rate can be controlled
Water control Inadequate Very precise and easy
Efficiency of
fertilizer use
Efficiency is low because of
heavy losses due to leaching
and runoff
Very high due to reduced loss of
nutrients through leaching and
runoff water
Soil erosion Soil erosion is high because of
large stream sizes used for
irrigation.
Partial wetting of soil surface and
slow application rates eliminate
any possibility of soil erosion
Increase in crop
yield
Non-uniformity in available
moisture reducing the crop yield
Frequent watering eliminates
moisture stress and yield can be
increased up to 15- 150% as
compared to conventional
methods of irrigation.

64. FERTIGATION
 Fertigation is the process of application of water soluble solid
fertilizer or liquid fertilizers through drip irrigation system.
 Through fertigation nutrients are applied directly into the wetted
volume of soil immediately below the emitter where root activity
is concentrated.
 Fertigation is practiced only in drip irrigation system. However,
fertilizer solution can be added with sprinkler irrigation system also.

65. FERTIGATION

66. Components of Fertigation
The main component of a fertigation is drip irrigation system. The
main components are :
(a) Venturi pump (injector)
(b) Fertilizer tank with flow bypass
(c) Pressure bypass tank
(d) Injection pump.

67. Advantages of Fertigation
1) The fertilizer solution is distributed evenly in the irrigation
network with the same uniformity as the irrigation water.
2) The availability of nutrients including micro-nutrients is high,
therefore the efficiency is very good.
3) The fertilizer system can also be used for other activities such as
incorporating acid to flush the drip system.
4) It eliminates the work of spreading fertilizer. Manual spreading of
fertilizer causes soil compaction and may damage the growing crop.

68. 1) Fertilizer placement is exactly to the root zone of plant and
can be uniformly applied through drip irrigation system.
2) All types of nutrients can be given simultaneously.
3) Lower doses of fertilizer could be applied daily or weekly (i.e.
a large number of split application) to avoid leaching and fixation
in soil.
4) Some liquid fertilizers are free of sodium and chloride salts, so
these are not harmful to soil.
5) Optimum production in light soil is possible.

69. 1) Spraying with liquid fertilizer is possible.
2) Liquid fertilizers are immediately available to plants.
3) Fertilizer use efficiency can be increased by 25 to 30% over
the tradition method of fertilizer application.
4) It decreases labour and energy cost.
5) The quality and quantity of crop production can be improved

70. Limitations
 The main one is the danger of poisoning people who drink the
irrigation water particularly laborers those work on the farm.
 It is therefore necessary to warn the people in the field about
drinking water separately and put up warning signs.
 Toxicity and Contamination
 Fertilizer Suitability
 Corrosion

71. •Well and Tank Irrigation

72. Well Irrigation

75. Well Irrigation
• It is a type of lift irrigation extracting water from the open well and tube
well.
OPEN WELL
• An open well is a vertical hole dug in the ground to obtain the subsoil
water
• The diameter of open well vary from 2 to 9m and depth less than 20m.
• It has small discharge capacity, usually 3 to 6 litres/sec
• It draws water from one pervious stratum only.
• The contribution of water is from the bottom and sides in the case of an
unlined well and from the bottom only in the case of a lined well.
• The open well may be classified into two types
1. Shallow open well
2. Deep open well

76. Well Irrigation
Shallow and Deep open well
• Shallow well rests in a pervious stratum and draws in supply from the
surrounding materials
• Deep open well rests on a impervious clay layer, through a bore hole made
into it.
• Pervious formation below the clay layer contain greater quantities of ground
water and greater discharge can be obtained from deep open well.

77. Well Irrigation
• A tube well is a deeper well over 15m deep and water is lifted with the help
of pump set operated by electric motor or diesel engine.
• It is a smaller diameter, large discharging well, usually 40-45litres/sec.
• Shallow tube wells having 20 to 70m depth and tapping only one aquifer
gives a yield of 15-20 litres/sec.
• Deep tube wells having 70 – 300m depth
• The main factors for tube well constructions
1. Extensive water bearing formation of adequate depth because a tube
well can irrigate 2 hectares per day and 0.2 hectares per day by an open
well
2. If the water table is more than 50 m deep, the cost of pumping unit for
tube well becomes uneconomic
3. There should be electric supply to run the tube well
TUBE WELL

78. Well Irrigation
• Tube wells are classified into three types based on the entry of water through a
cavity or a screen such as
1. Cavity type tube well
2. Strainer type tube well
3. Slotted type tube well
1. Cavity Type tube well

79. Well Irrigation
1. Cavity Type tube well
• Cavity type tube well draws water from the bottom of the well and not
from the sides.
• The flow in a cavity well is spherical.
• It consists of a pipe bored through the soil and resting on the bottom
of a strong clay layer (i.e.) The impervious layer is punctured and a
cavity is developed by pumping.
• In the initial stage of pumping, fine sand comes out with water and
consequently a cavity is formed.
• After cavity gets formed at the bottom and the water from the aquifer
enters the well pipe through this cavity.
• Cavity type tube wells can be used for small supplies particularly for
domestic purpose.

80. Well Irrigation
2. Strainer Type tube well

81. Well Irrigation
2. Strainer Type tube well
• It is the most commonly used type of tube well in our country.
• This tube well consists of plain or blind pipes and strainer pipes or
screen pipes
• Strainer type well uses strainer lengths lowered into the bore hole and
located opposite the water bearing formation where as the plain pipe
lengths are located opposite the non-water bearing formation.
• Water enters into the well through these strainers from the sides and the
flow is radial.
• Strainer consists of perforations with a wire mesh wrapped around the
pipe.
• Wire screen prevents the sand particles from entering the well.
• The well is generally plugged at bottom by cement concrete.

83. Well Irrigation
3. Slotted Type tube well

84. Well Irrigation
3. Slotted Type tube well
• A slotted pipe tube well uses a slotted pipe without being covered by any
wire mesh.
• Such slotted pipe length are located opposite the water bearing formation as it
is done with the strainers in a strainer type tube well.
• Gravel packing is required around the screen pipes in the entire depth of well.

85. Three types of pumps are generally used to lift water from tube well.
1. Centrifugal pump.
2. Bore hole type pumps (Submersible pump and turbine type)
3. Jet pumps
Centrifugal pump can be used when the maximum suction head is
upto 8m. Bore hole type consists of centrifugal pump with impellers
connected in series, mounted on vertical shaft and driven by motor.
In a submersible pumps, the motor and the pump are both attached
together and lowered inside the bore whereas in a turbine type, the pump
is driven by a direct coupled electric motor. Shaft is placed at the top of
line shaft at the ground level.
Jet pump consists of a combination of centrifugal pump and a jet
mechanism or ejector to increase the velocity of flow which creates
pressure area to draw more water from well.

86. Well Irrigation
Methods of lifting water from wells
1. Lifting of water from open well
2. Lifting of water from shallow tube well
3. Lifting of water from deep tube well
1. Lifting of water from open well
• The pump set (Pump and Motor) is installed at the
ground level and the strainer is provided sufficiently
below the static water level of the open well.

87. Well Irrigation
2. Lifting of water from shallow tube well
• The pump set is installed at the ground
level and a cap is provided on the the well
Top.
• A check valve is provided just below the
pipe connecting the pump with a tube well
As shown in fig.
• The supply of the water may be stopped
If the static water level goes below the such
As head.

88. Well Irrigation
3. Lifting of water from Deep tube well
• In this system, a submersible pumpset
Consists of electric motor an d a centrifugal
Turbine pump is lowered into the tube well
by suspended cable.
• It is placed sufficiently below the lowest
static water level as shown in fig.
• The water is available throughout the year
at constant flow rate.

89. Well Irrigation
Advantages of Well Irrigation
• Well is simples and cheapest source of irrigation and the poor farmer can
easily afford it.
• Well is an independent source of irrigation and it can be used as and when
the necessity rises.
• Well can be dug at any convenient place according to their requirement.
• The farmer need not pay anything to other agencies for doing well irrigation

90. Well Irrigation
Disadvantages of Well Irrigation
• Only limited area can be irrigated. Normally a well can irrigate 1 to 8
hectares of land
• Well may dry up and may be rendered useless for irrigation when excessive
water is taken out
• When drought comes, the ground water level falls and enough water is not
available in the well
• Tube wells can draw a lot of ground water from its neighbouring areas and
make the ground dry and unfit for agriculture
• Well irrigation is not possible in areas of salty ground water.

91. Tank Irrigation
• Tanks are small sized reservoirs(a small lake or pool )formed by
small earthern embankments to store runoff for irrigation.
• There is no technical difference between a reservoir and a tank
except that a large sized tank will be termed as reservoir.
• Reservoir generally will be formed by dams of any material
(Masonry, Concrete or Earth) whereas a tank is formed by earth
dams or earthern bunds only.
• Most of the tanks having maximum depth of 4.5 m while few are
as deep as 9 m.
• When the tank depth exceeds 12m, then it is referred to as a
reservoir.

92.  Andhra Pradesh has the largest area (29%) of tank irrigation in India
followed by Tamil nadu (23%).
 Tanks are known as Ery in Tamil. The temple tanks of Tamil Nadu
are known as Kulam.

93. Kinds of Tanks
Based on nature of supply of water:
1)System Tanks
2)Non-System Tanks
3)Grouped Tank or Tank in series
System Tanks
 The canal fed tanks are known as System Tanks, which were exclusively
under the management of the Public Works Department.
 The System Tanks are fed with water from rivers and run off through
diversion weirs, feeder channels and surface flow.
 System Tanks are the minority of tanks that are supplied from major
storage canal irrigation systems or from perennial rivers.

94. System Tanks

95. Non System Tanks or Isolated Tanks or Rainfed Tanks
 The rain fed tanks are known as Non-System Tanks.
 Non System Tanks which command area below 40 hectares
are coming under the control of Panchayat Unions.
 These Non-System Tanks have a small storage capacity.

96. Non System
Tanks

97. 3. Grouped Tank or Tank in series
• These tanks consists of a series of tanks connected together such
that out flow from the upper tank is stored in the lower tank for
irrigation.
• These tanks either receives the surplus water of the upper tank or
send its own surplus into some lower tank or do both.
• When a tank neither receives the water from the upper tank nor
discharges its own surplus into a lower tank is called as isolated
tank.

99. Tank Irrigation
• Irrigation tanks are classified based on size
1. Small tank
• 4.5 m height and 20 hectares area
2. Medium tank
• 9m height and 21 to 500 hectares area
3. Large tank
• 12 m height and more than 500 hectares area
• A tank irrigation system consist of
1. Earthern or Tank Bund for water storage
2. A Surplus Weir to dispose off flood discharge
3. Tank Outlets or Supply Sluices to feed the channels
4. Channels from the sluices to feed the irrigation area.

100. It is a small sized earth dam and its design and construction should be
carried out in accordance with principles applicable to earth dams. The
tank bunds may be of three types:
I. Earthern or Tank Bunds for Water Storage:
1. Homogeneous Embankment type
2. Zone embankment type
3. Diaphragm type

101. 1. Homogeneous Embankment type

102. 2. Zone embankment type

104. 3. Diaphragm type

106. • Structure constructed to provide passage to excess water is called
escape weir. It is also called tank surplus weir. The water starts spilling
over the weir as soon as tank is filled upto its crest.
• However, temporarily due to rush of incoming water the level in the
tank rises above F.T.L.
• The new level reached is called Maximum Water Level (M.W.L). It
depends on the extent of flood. For design purposes M.W.L is calculated
taking into account maximum flood discharge likely to occur
• It is therefore necessary to make suitable arrangement to pass down
excess water beyond Full Tank level (F.T.L.) safely.
II. Tank Weir or Surplus Weir

109. III. Tank Sluice or Tank Outlet:
 For releasing stored water into irrigation channel, opening is
provided in a tank bund. It is constructed in the form of a
culvert or a pipe line.
 Since the opening extends from upstream face of the bund to the
downstream face, wing walls and other types of bank connections
are necessary at the head as well as tail of the opening. In small
tanks, pipe outlets are constructed. For medium sized
tanks masonry culverts are adopted.

110. i. Pipe Outlets:
• Either cast iron pipes or cement or earthenware pipes are used to
construct pipe outlets or pipe sluices. Since the size of pipes is
small they are not open to inspection once they are put in place
through the bund.
• To avoid their bursting or leakage in pipes they are used in small
tanks where depth of water stored in less than 2.5 metres
approximately.
• Any repair work in this type is possible only after bund is cut
open.

116. ii. Culvert Type Sluice:
In this type masonry culvert of minimum size 0.6 metres
wide and 0.75 metres high is constructed either with or without
arch roof. The size of the culvert depends upon the water to be
conveyed. The minimum size of 0.6 × 0.75 m permits, manual
inspection and repairs, and cleaning from inside.

118. Furrow method of irrigation is most suitable for
a) potatoes
b) rice
c) wheat
d) Cotton

119. The canal which is not supposed to do any irrigation is
called
a) main canal
b) water course
c) major distributary
d) minor distributary

129. • Irrigation scheduling is the process used by irrigation system
managers to determine the correct frequency and duration of
watering.
• Irrigation scheduling is the decision of when and how much
water to apply to a field.
• Its purpose is to maximize irrigation efficiencies by applying
the exact amount of water needed to replenish the soil moisture to
the desired level.
• The importance of irrigation scheduling is that it enables the
irrigator to apply the exact amount of water to achieve the goal.
Irrigation scheduling

131. Advantages of Irrigation Scheduling
 It enables the farmer to schedule water rotation among the various
fields to minimize crop water stress and maximize yields.
 It reduces the farmer’s cost of water and labour
 It lowers fertilizer costs by holding surface runoff
 It increases net returns by increasing crop yields and crop
quality.
 It minimizes water-logging problems
 It assists in controlling root zone salinity problems
 It results in additional returns by using the “saved” water to irrigate
non-cash crops

132. The aim of irrigation scheduling is to apply the right
amount of water, in the right place at the right time
to achieve optimum yields.

133. Various methods and tools have been developed to
determine when crops require water and how much
irrigation water needs to be applied. Most commonly
and currently use methods are
(a) Water Balance Method
(b) Soil Moisture measuring – Tensiometers and
electrical resistance meters
Irrigation Scheduling Methods

134. Swi + P + Irr = Swf + R + DP + ET
Swi – Swf = R + DP + ET - P - Irr
(a)Water Balance Method

135. (b) Soil Moisture measuring

137. (b) Soil Moisture measuring

142. Water distribution in irrigation systems
The irrigation system consists of a (main) intake structure or
(main) pumping station, a conveyance system, a distribution system,
a field application system, and a drainage system.

144. Methods of Water distribution in
canal irrigation systems
• Rational water distribution system or Warabandi
• Intermittent flow
• Continuous flow
• Demand based

148. Water distribution system

151. BORDER IRRIGATION

152. CHOICE OF METHOD OF IRRIGATION
 Natural conditions (slope & soil type).
 Type of crop,
 Level of technology that is available,
 Previous experience with the practice of irrigation and
 Required labour inputs.

153. Irrigation Efficiencies
 Efficiency is the ratio of the water output to the water input,
and is usually expressed as percentage.
 Input minus output is nothing but losses, and hence, if Losses
are more, output is less and, therefore, efficiency is less.
Hence, efficiency is inversely proportional to the losses.
 Water is lost in irrigation during various processes and,
therefore, there are different kinds of irrigation efficiencies

154. Kinds of irrigation efficiencies
1)Efficiency of Water-conveyance
2)Efficiency of Water Application
3)Efficiency of Water Use
4)Efficiency of water storage
5)Water Distribution Efficiency

155. Efficiency of Water-conveyance (ηc)
It is the ratio of the water delivered into the fields from the outlet point of
the channel, to the water entering into the channel at its starting point. It
may be represented by ηc. It takes the conveyance or transit losses into
consideration.
ηc = (Wf/Wr) X 100
Where
ηc= Water conveyance efficiency,
Wf = Water delivered to the irrigated plot at field supply Channel,
Wr = Water diverted from the source ( river or reservoir )

156. Efficiency of Water Application (ηa)
It is ratio of water stored into the root zone of the crop to the
quantity of water delivered at the field (Farm).
ηa =Ws/Wf X 100
Where,
ηa = Water application efficiency,
Ws = Water stored at the root zone during the irrigation
Wf = Water delivered to the farm.

157. Efficiency of Water Use (ηu)
It is the ratio of the water beneficially used including leaching
water, to the Quantity of water delivered. It may be represented
by ηu
ηu = (Wu/Wd) X 100
Where,
ηu = Water use efficiency,
Wu = Beneficial use of water or consumptive.
Wa = Water delivered to the field.

158. Efficiency of water storage: (ηs)
The concept of water storage efficiency gives an insight to how
completely the required water has been stored in the root zone
during irrigation.
ηs = (Ws/Wn )X 100
Where,
ηs= Water storage efficiency,
Ws = water stored in the root zone during irrigation.
Wn = Water need in the root zone prior to irrigation.

159. Water Distribution Efficiency (ηd)
Water distribution efficiency evaluates the degree to which water is
uniformly distributed throughout the root zone.The more uniformly the
water is distributed , the better will be crop response.
ηd =100 (1-y/d)
Where,
ηd= Water distribution efficiency,
y= avg numerical deviation in depth of water stored from avg depth
stored in the root zone during irrigation
d = Avg depth of water stored during irrigation.

160. Consumptive use Efficiency (ηcu)
It is the ratio of consumptive use of water to the water depleted
from the root zone.
ηcu = (Wcu/Wd)X 100
Where,
ηcu= Consumptive use efficiency,
Wcu= Nominal consumptive use of water
Wd = Net amount of water depleted from the root zone soil.

161. Discussions ?