IRRIGATION METHODS

UNIT-II IRRIGATION
METHODS
SYLLABUS:
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.

TANK IRRIGATION
Irrigation practice carried out by irrigation tank is
called Tank irrigation.
It may be an artificial reservoir of any size.
This type of irrigation is used at the time of
monsoon seasons.
Our Tamil Nadu has the second place of using
tank irrigation next to Andhra Pradesh.

TANK IRRIGATION
Nellore and Warangal are the main districts
of tank irrigation.
Tamil Nadu has the second largest area of 589
thousand hectares under tank irrigation.
This is over 23 per cent of tank irrigated area of
India and about one-fifth of the
total irrigated area of the state.
There are about 24,000 tanks in Tamil Nadu.

Reasons for Tank Irrigation more common in
south India
Undulating topography of land, not possible to
make canal and wells.
Poor ground water availability.
Seasonal river(water sources)
Many streams are become torrential(more water
in rainy season), to make use of this water tank
constructed along the path of river streams.
The scattered availability of agricultural land.

Tanks and their Functions
1. Soil water conservation
2. Flood control
3. Drought mitigation
4. Protection of environment and surrounding area
Re-orient investment pattern towards tank-fed
agriculture:
Since the five year plan, all the five year plans
gave much important for the canal and well
irrigation sectors.

Due to the increase of poverty and marginal
farmers who depends on dry land and tank fed
agriculture, tank irrigation getting important.
The solution has to come up with the specific
area development approach for combining both
the tank fed and rain fed agriculture.

Merits & Demerits of Tank Irrigation
S.No Merits Demerits
1 Most of the tanks are
natural and do not involve
heavy cost for
construction.
Many tanks dry up
during dry seasons
2 Even individual farmer can
have his own tank.
Fail to provide irrigation
when its needed most.
3 Tanks are generally
constructed on rocky bed
have longer life span.
Silting of the tank bed is
a serious problem.

Merits & Demerits of Tank Irrigation
S.No Merits Demerits
4 Fishing is also carried on
it.
Requires desilting of the
tank at regular intervals.
Evaporation takes place.
Cover the large area of
cultivable land.
Lifting water from tank
make some difficulties.

Capacity – 1474 million
cubic ft
Sluice nos- 10
Area – 8 km
Depth – 30.6 ft
Water spread area – 16.06
Km2
Irrigate land area – 6000
acres
KAVERIPAKKAM TANK

cubic ft
Sluice nos- 08
Depth – 24 ft
Water spread area – 16.06
Km2
Irrigate land area – 5428.8
hectares
CHEMBARAMBAKKAM TANK

cubic ft
Water spread area – 25
Km2
VEERANAM TANK

WELL IRRIGATION
Irrigation was done by using wells.
In order to reduce salinity, wells are dug near by
the ponds.
Well irrigation is mainly used in the alluvial
plains and where easy to dig.
Generally wells are dug in the middle of the land.
Well irrigation is implemented in two ways:
1. Open well/Dug well Irrigation
2. Tube well Irrigation

1.Open well/ Dug well Irrigation

1.Open well/ Dug well Irrigation
Shallow well – 3 to 5 mts
Deep well - 15 to 25 mts
There were about 5 million wells in 1950-51 and
now increased about 12 million.
Well irrigation are generally used about 60%,
canal irrigation about 29.2% and tank irrigation
4.6%
Uttar Pradesh has largest area of 93-84 lakh
hectares under well irrigation which accounts
about 28-19% well irrigated area of india.

This is followed by,
Rajasthan – 10 to 44%
Punjab - 8 to 65%
Madhya Pradesh – 7 to 97%
Gujarat – 7 to 34%
Bihar – 6 to 29%
Andhra Pradesh – 5 to 87%
Maharashtra – 5 to 75%
Haryana – 4 to 41%
Tamil Nadu – 4 to 35%
West Bengal – 4 to 19%
Karnataka – 3.06%

2.Tube Well Irrigation
o It is a deeper bore-well(greater than 15m to
100m) from which water is lifted with the help of
a pumps.
o Tube well is not possible to install all the places,
especially some geographical conditions.
Facts of Tube well:
There should be the sufficient ground water
available, because this methods is irrigates 2
hectares/ day against normal irrigation done by
0.2 hectares/day.

The water level should be nearly 15 m, if the
depth of water increases more than 50 m, the cost
of pumping out water from tube well getting
uneconomic.
There should be a regular supply of electricity or
diesel while using tube well.
The dug soil was used to fertility for land, it may
help to increase the production.

 The first tube well of India was sunk in Uttar
pradesh in 1930.
 Till 1951 tube well count = 2500 nos & it will
increased 3 million .
 Tamil Nadu has the largest numbers of tube well,
i.e, 11 lakhs.
Merits of Well and Tube well Irrigation
1. Well is the simplest and cheapest can be used
for the poor farmer also.
2. Well irrigation is the independent one, can be
access at the time of need.

3. Excessive irrigation by canal may lead problem
but which is not in the case with well irrigation.
4. There is a limit for canal lining but there is no
limit for well dug.
5. Several chemicals like nitrate, chloride, sulphate,
etc., are generally add in the well water, it is used
for the fertility purpose.
6. The farmers has to pay regularly for canal
irrigation, here no case of pay.

Demerits of well and tube well irrigation
1. Limited area can be irrigated (1 to 8 hect)
2. Well may be dry and after irrigation purpose it
may be rendered.
3. At the time of drought, ground water level falls
,so well water level also getting decreased.
4. Tube wells can take large quantity water from
the surrounding places, so the nearby places
unfit for agricultural.
5. The both types are not possible in areas of
blackish groundwater.

YIELD TEST OF AN OPEN WELL
1. Constant level pumping test
2. Recuperation test
1. Constant level pumping test
Pumping is carried out in the well with a suitable
pump with regulating arrangement.
The water level is ‘h’ known as draw down
(or)depression head.
The speed of the pump is regulated & the water level
is maintained in the well for a given time.
At the same time quantity of water pumped out is
measured with V- notch , it is measured (Yield of the
well= m3/hr)

Discharge is given by,
Q = A x V
Q = A x ( Cxh)
Where,
Q = discharge (m3/sec)
A = Area of cross section of well at bottom (m2)
V = mean velocity of water (m/sec)
h = depression head
C = Percolation intensity coefficient

2.Recuperation Test
This types of test is carried out at the place of
regulate the pump is not possible to maintain the
constant level.
In this test, water level is depressed to any level
below the normal level of water and the pumping
is stopped.
The time taken for the water to recuperate to the
normal level is noted.
The discharge(Q) is calculated from the data
given below:

Let, aa – static water level in well before pumping
started
bb – water level when pumping stopped
cc – water level at time ‘T’ after pumping
stopped
h1 –depression head, when pumping stopped
h2 –depression head at time ‘T’ after pumping
stopped in ‘m’
s –depression head at time ‘t’ after pumping
stopped in ‘m’
t,T – Time (hrs)
dh – change in depression head in change in
time dt

Q= K H = [K/A] A.s
Where,
K/A – Specific yield
𝐾
𝐴
=
2.303
𝑇
log⁡10(
ℎ1
ℎ2
)
⁘ Q=
2.303
𝑇
log 10
ℎ1
ℎ2
𝐴. 𝑠
Where,
K/A = 0.25 for clay
K/A = 0.50 for fine sand
K/A = 1.00 course sand
It T = secs, Q= m3/sec. Discharge ‘Q’ corresponds to
the depression head ‘s’.

Types & methods of irrigation
Irrigation has been classified into two main types,
based on water source available.
1. Flow Irrigation
2. Lift Irrigation
1. Flow Irrigation
The available water(mainly surface water) is
conveyed to the crops by gravity flow pattern.
(a) Perennial Irrigation
(b) Flood Irrigation or Inundation Irrigation

(a)Perennial Irrigation
In this type of source of water is from a river
which is perennial. A weir or barrage is
constructed across this river.
Sometimes dam may be constructed to form a
reservoir upstream.
Main canal with a regulator is constructed
where one or both banks supply water to the
crop field.
This type is reliable as water is available during
the whole period of the year.

(b)Flood Irrigation or Inundation Irrigation

In this type of irrigation, the cultivated land is
flooded with water & dried be the planting of the
crop.
It is further subdivided into 3 types based on the
source of water supplied to the crops.
i. Direct irrigation (or) River canal irrigation –
diversion type
ii. Storage irrigation(Reservoir or tank irrigation-
storage type)
iii. Combined storage & diversion type.

i) Direct irrigation (or) River canal irrigation –
diversion type:
 InDirect Irrigation no storage of water
upstream of diversion weir is provided. Water
is directly diverted to canals, without any
storage. Water through the canals with
regulators is diverted directly to the canals.
ii) Storage or Tank Irrigation:
In this method, water is stored in dam or weir and
used to irrigation purposes.
The capacity of the dam or weir is based on the
crop-water requirements.

Direct irrigation (or) River canal irrigation –
diversion type

iii) Combined storage cum diversion scheme:
In this method first the water is stored in the
reservoir or dam.
The water is discharged from dam & used to
hydroelectric power generation.

2.Lift Irrigation
In this method of irrigation, the water is lifted
from the well and conveyed to the agricultural
field for cultivation.
The adaptation of any particular methods of
irrigation depends upon the following factors,
1) Uniform distribution of water
2) Large concentrated water flow
3) Economic conveyance of water with suitable
structure
4) Mechanised farming

I. Surface Irrigation
It refers application of water conveyed on to the
land surface.
This method is subdivided into three types.
a) Flooding method
b) Furrow method
c) Contour farming

I.a)FloodingMethod
• The flooding method is subdivided into various
methods as:
• FreeFlooding
 With the help of field channels, agricultural land
is divided into small strips . Field channels are
provided with the field regulator.
 This method is known as irrigation by plots
commonly used in India.
 In this method when the strips are flooded with
water, surplus water is allowed to enter the water
channel and allowed to discharge in the water
downstream.

BasinFlooding
• This method is used frequently to irrigate the
or chards. It is a special type of check flooding
method. Each plant is enclosed by circular
channels which is called basin. Basins are
connected to small field ditches.
• Ditches are fed from the main supply channel.
When the basin are flooded, the supply is
stopped. Portable pipes or large hoses may also
be used in place of ditches to flood the basin

Check Flooding
 In check flooding the crop area is divided into
some plots which are relatively leveled by
checks or bunds water from field channels is
allowed to enter to each plot or check basin
and the plots are flooded to the required depth.

BorderStrips
 In this method, the agricultural area is divided
into series of long narrow strips known as
border strips by levees, i.e. small bunds.
 The strips are aligned along the country slope
so that the water can flow easily throughout the
area.
 This method is suitable when the area is at level
with gentle country slope.

Zig-Zag Method
 In this method, the agricultural area is sub-
divided into small plots by low bunds in a zig-
zag manner.
 The water is supplied to the plots from the field
channel through the openings.
 The water flows in a zig-zag way to cover the
entire area. When the desired depth is attained,
the openings are closed.

I b).Furrow Method
• In this method, irrigation water is useful for
row crops. Narrow channels are dug at
regular intervals.
• Water from the main supply is allowed to enter
these small channels or furrows. Water from
the furrows infiltrates into soil and spread
laterally to saturate the root zone of the crops.
It is suitable for row crops like potatoes,
sugarcane, tobacco, maize, groundnut, cotton,
etc..

This method has the followingadvantages:
• Less water is required as water comes
in contact of 1/5 to ½ of the land surface.
• Evaporation loss is less.
• Labor requirement for land preparation
and irrigation is less.
• Wastage of water is minimum.
• It is suitable for row crops.

Ic) .Contour Farming
 Contour farming is practiced in hilly areas with
slopes and with falling contour.
 The land is divided into series of horizontal
strips called terraces. Small bunds are
constructed at the end of each terrace to hold
water up to equal height.
 Contour farming besides producing crop yields,
helps in mitigating indirectly controlling flood,
soil conservation.

II.SprinklerIrrigation Method
• In this method, water is applied to the crop in
the form of sprinkle or spray with the
combination of pump, main pipe, sub-main
pipe, lateral, riser, nozzle, etc..
• It is a kind of artificial rainfall and therefore, it
is very fruitful for crops grown in afarm.

Conditions Favoring the Adoption of Sprinkler
Method
(i)When the land topography is irregular, and hence
unsuitable for surface irrigation.
(ii)When the land gradient is steeper, and soil is
easily erodible.
(iii)When the land soil is excessively permeable, so as
not to permit good water distribution by surface
irrigation; or when the soil is highly impermeable.
(iv)When the water table is high.
(v)When the area is such that the seasonal water
requirement is low, such as near the coasts.

(vi) When the crops to be grown are such:
(a)as to require humidity control, as in
tobacco;
(b)crops having shallow roots; or
(c)crops requiring high and frequent
irrigation.
(vii) When the water is available with difficulty and
is scarce.

Advantagesof Sprinkler Irrigation
• Erosion of soil is avoided or controlled
• It is possible to apply water uniformly
• Irrigation of water better controlled according
to need of the crops in their different stages of
growth.
• There is no surface run-off
• Labor cost is less
• Damage of crop due to frost isreduced.
• It is a standby drainage pumping set
• It can be used even with high watertable.

• Seepage loss like earthen canal are eliminated
• Fertilizers can be uniformly applied by mixing
withwater.
• Efficiency is higher,
• i.e. Efficiency = Water stored in root zone
Water sprinkled

Dis-Advantagesof Sprinkler Irrigation
 Although this method has number of
advantages, yet it has some limitations
• Wind may disturb or distort sprinklingpattern
• A constant water supply is needed for
commercial use of equipment.
• Water is to be clean and free from sand.
• Heavy soil with pore intake cannot be irrigated
efficiently.
• Areas with higher temperature increase
evaporation loss
• They are not suitablefor crops requiring
frequent and deep water depth.
• It requires high electrical power.

iII. Sub-Surface Method
 In this method, the water is applied to the root
zone of the crops by underground network of
pipes.
 The network consists of main pipe, sub- main
pipes, and lateral perforated pipes. The
perforated pipes allow the water to drip out
slowly and thus the soil below the root zone of
the crops absorbs water continuously.
 This method is suitable for permeable soil like
sandy soil. The method is also known as drip
method or trickle method of irrigation.

Sub-surface irrigation is limited to the areas where:
O soil is relatively permeable for a considerable
depth, surface slopes are gentle
O natural drainage is restricted
O It is practical to hold groundwater table at a
particular depth.

Drip or Trickle Irrigation
• It has been shown that sprinkler irrigation is not
suitable in the region of high temperature, high
wind velocity and low humidity due to excess
loss by evaporation.
• In such regions drip or trickle irrigation is most
suitable.
• This method was first developed by Israel and is
rapidly gaining importance all over the world.
.

 This method consist of carrying the irrigation
water through pipe and water is allowed to drip
or trickle in the root zone of the crop under low
pressure.
 Two different pipes are used in this method. A
perforated plastic pipe is laid along the ground
at the base of a row of crops or plants.
 The perforation are designed are designed to
emit a trickle and spaced to produce a wetted
strip along the crop row.

• In the second system, Irrigation water is
conveyed through a larger feeder pipe below
the ground and is allowed to drip at the root
zone of the crop slowly through nozzle or
orifice practically at low pressure. Thus root
zone is kept constantly wet.

Componentsof Drip Irrigation
• A pump to lift water from source to overhead
tank.
• An overhead tank to store water to maintain a
pressure head of5m to 7 m.
• Central distribution system comprising fertilizer
tank, filter and water regulator.
• Main and secondary pipes made of P.V.C.
diameter may vary from 2 cm to 4 cm
depending on water to be supplied.
• Trickle lines consists of 1 cm to 2 cm diameter
with perforation where nozzles are fitted.

• Plastic nozzles having perforation are attached
to laterals.
• Size of overhead tank and pipes depend on
requirement of water in the crop field.
• The spacing between laterals and nozzle is
governed by type of crop.
• Growth stage of crop, type of soil, interval of
crop row and agro-technicalpractices.

Advantages of Drip Irrigation
• Excellent control of water is possible as water is
possible as water can be applied at the rate to
the consumptive use of water.
• Evaporation from soil is reduced to minimum.
• Deep percolation of water is entirely eliminated.
• Nutrients can be applied directly to plant roots
by adding liquid fertilizers to the water.
• Salinity problems does not arise.
• Although initial cost is high, maintenance and
labor may be low once the system is set up.
• It is best method to reclaim desert areas
• It is not affected by the action of wind
• Soil erosion and tail water loss do not take place.

• Weed growth control is possible.
• It can be used for uneven topography.
• Lessrequirement of water as loss is minimum.
• Insect and pest control chemicals can be directly
applied to the root zone
• No over irrigation takes place.
• Method is specially suitable for cash crop like
vegetables, fruits tobacco, cotton, etc..
• Due to control supply, water logging is avoided.

Dis-Advantages of Drip Irrigation
• Application of insoluble fertilizers like super-
sulphonate, etc., is not possible readily through flow
system.
• Heavy rainfall may push downward the accumulated
salts at the edge of wetted zone. This may affect the
crop growth if this salt comes to the root zone.
• Dripper or nozzles blockages is likely to occur by soil
particles, as the size of nozzle varies from 0.5 to 2 mm.
• Due to high initial cost, farmers normally do not prefer
this method.
• It is only suitable for close growing crops like
vegetables, etc..
• Frequent change of trickle lines are necessary as
spacing of nozzle is different for types of crops.

MICRO IRRIGATION
It is a scientific method of irrigation which
carries desired quantity of water & nutrients to
the root zone of the plant. (Eg: Drip Irrigation)
Advantages:
O Better quality
O Yield increases upto 230%
O Saves water upto 70%
O Successfully working more than 40 crops
covering more than 600 thousand acres.

DESIGN OF DRIP IRRIGATION
The following steps are involved in the design of
drip irrigation;
1) Inventory of the resources & data collection
2) Computation of peak crop water requirement
3) Deciding the appropriate layout of the drip
irrigation system
4) Selection of emitters
5) Hydraulic design of the system interms of
lateral, sub main and main
6) Horse power requirement of pump

1) Inventory of the resources & data collection
Water resources – quantity and type of water
resources available
Land resources – topography of land & other
parameters
Climate – condition of climate for computation of
crop water requirement
Crop – types and fertility available details.

2) Peak crop water requirement
Irrigation interval and types of crop required.
The crop water requirement is maximum during
any one of the three seasons is adopted.
The daily water requirement for fully grown
plants can be calculated;
𝑽 = 𝑬𝑻𝒓 + 𝑲𝒄 + 𝑨⁡𝒙⁡𝑾𝒑
Net volume of water to be applied;
𝑽 𝒏 = 𝑽⁡ − 𝑹𝒆 + 𝑨⁡𝒙⁡𝑾𝒑
Number of daily operating hours of the system
𝑻 =
𝑽 𝒏
𝑵 𝒆⁡
𝒙⁡𝑵𝒑𝒙⁡𝒒

Where,
V – volume of water required (L)
ETr – reference crop evapotranspiration (mm/day)
Kc – crop coefficient
A – area occupied by a plant(row to row spacing x
plant to plant spacing), (m2)
Re – effective rainfall, (mm)
Wp – wetting fraction (varies for 0.2 for wide
spaced and 1.0 for close spaced crops)
Ne – number of emitters per plant
Np – number of plants
q – emitter discharge, L3s-1

3) Layout of drip irrigation system
Based on the area, the requirement of high
discharge may not be possible.
So there should be provide more numbers of
mains and sub-main pipes with regulating valves.
These mains and sub-main pipes are further
connected to the subunits with regulating valves
for discharge.
Number of subunits = total time available for
irrigation / time of operation of system(drip)
Total time available for irrigation depends upon
the availability of electricity or diesel
engine/generator, etc..,

If the available discharge is more, the subunits
are regulated the discharge.

4)Selection of Emitters
The selection of emitters depends on the following;
Soil- discharge is less than the infiltration rate of
soil & heavier soil may increase the spacing of
emitters.
Crop – In case of row crops single exit emitters
are used & multi exit emitters are used for
plantation crops.
Topography –Pressure compensating emitters
are used for uneven topography.
Emission uniformity – pressure compensating
emitters are more preferable than non- pressure
compensating emitters.

Discharge available – when low discharge need,
emitters with low discharge is to be used.
Water use efficiency – subsurface drip irrigation
reduces the evaporation loss than surface drip
irrigation.
Water quality – Emitters with more dia or cross
sectional area to be used for the water with heavy
load suspended solids.

5)Hydraulic design of pipe network
In this pressure distribution takes main place. i.e,
if the pressure will increase the discharge also
increase through the emitters.
Only pressure compensating emitters are capable
to provide same discharge but it is expensive.
So the alternative is the non- pressure
compensating emitters are found.
In practical point of view, the flow variation of
water pressure can be minimized by suitable
hydraulic design.

As per the principle of hydraulics, the minimum
pressure variation along sub-main can be
obtained by keeping dia of the pipes are more
and length of the pipe is small. This is expensive.
The alternate way is, less dia with more length .
If two emitters are there the discharge allowance
to 10%. This is equivalent to the 20% pressure
variation in turbulent emitters and 10-15%
variation in long path emitters.
Overall 55% head loss allowed in laterals and
45% in the sub main.

The procedure of hydraulic design consists of;
 Know the operating pressure of emitters
 Find out the allowable head loss in lateral and
sub-main
 Find out the lateral and sub-main discharge
 Find out the dia and length of lateral pipes. For
this purpose find out head loss by Hazen william
or Darcy-weisbach formula.
 Repeat the procedure for the sub-main
 Find out the diameter of main so that the velocity
is within the allowable limit.

Computation of discharge in lateral, sub-main
and main
Flow carried by each lateral line,
Q1 = discharge of one emitter
Flow carried by each sub-main line, Q= Q1x No.of
lateral lines per sub-main
Flow carried by main, Q = Q1 x No.of sub main
line
i) Head loss in laterals:
The head loss evaluated with the help of Hazen-
william empirical equation,

𝑯 𝒇 𝟏𝟎𝟎 = 𝑲
𝑸
𝑪
𝟏. 𝟖𝟓𝟐 𝒙𝑫
− 𝟒. 𝟖𝟕𝟏 𝒙𝑭
As the length of the pipe increases the discharge
decreases. For this reason, a reduction factor
‘F’ which is less than 1.0
Head loss for the specified length of pipe is,
𝑯 𝒇𝒍 = 𝑯𝒇 ∗
(𝑳 + 𝑳𝒆)
𝟏𝟎𝟎
Where,
Hf(100) – head loss due to friction per 100m
Hfl – head loss in the specified length of lateral

Q – flow of water in pipe, Ls-1
D – internal dia of pipe, cm
L – length of pipe, m
C – Hazen-william constant (140 for PVC pipe)
K – 1.22x 1012
Le – equivalent length of the pipe
Ne – number of emitters on a lateral
fe – equivalent length due to one emitter connection
fe - 1 to 3m for in line emitter with barbed
connection
F – reduction factor due to multiple opening

𝑭 = 𝟏/(𝒎 + 𝟏) +
𝟏
𝟐𝑵
+ ( 𝒎 −1)/6N2
Where,
N – number of outlets on lateral
ii) Head loss in sub-mains
The energy loss in the sub-main is same as used
for lateral.
The Hazen williams roughness coefficient(C)
varies between 140 and 150.
The sub-main and mainline pipe was
hydraulically smooth due to PVC and HDPE pipe
materials.

iii) Head loss in main line
The pressure controls are provided at the sub
main inlet.
So energy loss is not affect the system
uniformity(F=1).
The frictional head loss in main line is calculated
by the same equation Darcy-weisbach formula or
Hazen-william empirical equation.

6)Horse power requirement of pump
ℎ 𝑝 =
𝐻⁡𝑥⁡𝑄𝑚
75⁡𝑥⁡η 𝑝⁡𝑥⁡η 𝑚
Where,
H – total pumping head (Hf+He+Hs), m
Hf – total head loss due to friction, m
He – operating pressure head required at the emitter, m
Hs – total static head, m
Qm – discharge of main
hp – efficiency of pump
hm – efficiency of motor

DESIGN OF SPRINKLER IRRIGATION SYSTEM
i) GENERAL RULES
 Main should be laid up
 Laterals should be laid across the slope
 For multiple laterals, lateral dia should not be
more than 2 dia.
 Water supply source should be nearest to the
center of the area.
 Booster pump required at high pressure places.
 Layout should be modified.

ii) Selecting the sprinkler systems
The crops are to be cultivated.
The shape and size of the field.
The topography of the field
The time and labor available.
iii) Selection sprinkler system capacity
Peak crop water requirements
Effective crop rooting depth
Texture and infiltration rate of soil
Available water holding capacity of soil
Pumping capacity of the water source

iv) Operation and maintenance of sprinkler
systems
Operations:
The main and lateral pipes always being laying
with pump.
While joining couplings, ensured that both the
couplings and the rubber seal rings are clean.
Starting the sprinkler system, ensure that the
pump attained the pressure level for producing
output.
Then only the delivery valve will be open,
similarly the delivery valve is closed after
stopping the power unit.

After stopping the system, the pipes and sprinkler
lines are shifted any where.
Dismantling of system should be in the reverse
order of system arranging.
Maintenance:
1. Pipe and fittings:
• Fittings are checked clean and dry which the
rubber sealing ring fits.
• Keep all nuts and bolts tight.
• Do not lay pipes on the new concrete and do not
lay fertilizer sacks on the pipes.

2. Sprinkler heads:
• When moving sprinkler lines, make sure
sprinklers are not damaged.
• Do not apply oil or grease or any lubricant
materials.
• Sprinklers have sealed bearing and at the bottom
of the bearing there are washers.
• Check the washers regularly and replace the
washers if damaged.
• After several season’s operation the swing arm
spring may tightening. It is maintained by pulling
out the spring and re-bending it.

v) Storage
Remove the sprinklers and store in a cool, dry
place.
Remove the rubber sealing rings from couplers
and fittings and store in a cool , dark place.
The pipes are stored outdoors or in racks with
one end higher than the other.
Disconnect the suction and delivery pipes from
the pump.
After disconnecting apply lubricants and rotate
pump for few minutes & it will prevent from the
rusting of pump.

vi) Trouble shooting:
1. Pump does not prime or develop pressure:
Check the all valves before and running stages of
the pump.
2. Sprinklers do not turn:
Check the nozzles thoroughly ( blocks, swings,
spring tension about 6mm)
3. Leakage from coupler of fittings:
Check the couplers and fittings properly.

IRRIGATION SCHEDULING
It is the process used by irrigation system
managers to determine the correct frequency and
duration of watering.
The following factors may be considered:
How quickly water applied.
Uniformity of irrigation system
Soil infiltration rate
Slope of the land
Soil available water capacity
Effective root depth of water provided

Amount of time water or labor available
Available moisture content
Irrigation scheduling concept:
1. How much to irrigate
2. How often to irrigate
Advantages:
Schedule the water rotation and minimize the
loss with increase the yield.
Reduces the cost of farmer’s to pay amount for
water.
Reduces the fertility surface runoff.

It minimizes the water logging problems.
Control the root zone salinity problems.
The additional saved water used for further
irrigation purpose.
Methods of irrigation scheduling:
1. Soil indicators – field capacity of soil
2. Climatological – (IW/CPE = 1.0)
3. Plant indices – visual, plant water(energy
measurements) , canopy temperature(internal
water balance)
4. Water balance – weather, crop and soil
information.

WATER DISTRIBUTION SYSTEM
Systematic distribution of water plays a key role
in agricultural crop production.
Methods of distribution system:
1. Conventional system
2. Irrigation schedule system
1. Conventional system:
 The area is divided into different blocks and
water irrigated to blocks depending upon the
available head and discharge required.

 Then select the diameter of the pipes for
irrigation. (design dia is less than the available
dia)
 Valves are fitted on a pipe by constructing the
field delivery chambers.
 Water is distributed from the Main Delivery
Chamber(MDC) as per time table & flow is
controlled by valves.
2.Irrigation schedule system:
 This system is similar to the previous system, but
one difference is different blocks are irrigated
one by one per day.

 The dia of the pipe is higher than the
conventional system.
 No need of control valves.
 Every farmer has the uniform distribution of
water supply to their crops.

IRRIGATION EFFICIENCIES
1. Water conveyance efficiency(ηc)
2. Water storage efficiency (ηs)
3. Water use efficiency (ηu)
4. Water application efficiency (ηa)
5. Water distribution efficiency (ηd)
1.Water conveyance efficiency(ηc)
 It is defined as the ratio of water delivered into
the irrigation field to the water entering into the
channel.

𝜼 𝒄 =
𝑾 𝒇
𝑾 𝒄
∗100
Where,
ηc - water conveyance efficiency
Wf – water delivered to the field
Wc – water entering into the channel
2.Water storage efficiency (ηs)
𝜼 𝒔 =
𝑾 𝒔
𝑾 𝒏
∗100
ηs - water storage efficiency
Ws – water stored in root during irrigation
Wn – water needed in the root zone prior to
irrigation

3. Water use efficiency (ηu)
𝜼 𝒖 =
𝑾 𝒖
𝑾 𝒅
∗100
ηu - water use efficiency
Wu – water used beneficially
Wd – water delivered
4.Water application efficiency (ηa)
𝜼 𝒂 =
𝑾 𝒔
𝑾 𝒇
∗100
ηu - water application efficiency
Ws – water stored in root during irrigation
Wf – water delivered to the field

5.Water distribution efficiency (ηd)
It denotes the degree of uniform distribution of
water to the root zone.
𝜼 𝒅 = 𝟏 −
𝒚
𝒅
∗ 𝟏𝟎𝟎
Where,
ηd - Water distribution efficiency
y - average numerical deviation in depth of water
stored from average depth during irrigation.
d - average depth of water stored during irrigation.

IRRIGATION METHODS

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