Civil Engineering Department

2nd year

Report In : Sprinkler Irrigation

Name: ‫محمد عادل محمد دياب‬

Sec : 2

B.N : 24

SPRINKLER IRRIGATION
Introduction
In the sprinkler method of irrigation, water is sprayed into the air and allowed to fall
on the ground surface somewhat resembling rainfall. The spray is developed by the
flow of water under pressure through small orifices or nozzles. The pressure is usually
obtained by pumping. With careful selection of nozzle sizes, operating pressure and
sprinkler spacing the amount of irrigation water required to refill the crop root zone
can be applied nearly uniform at the rate to suit the infiltration rate of soil.

Advantages of sprinkler irrigation

 Elimination of the channels for conveyance, therefore no conveyance loss
 Suitable to all types of soil except heavy clay
 Suitable for irrigating crops where the plant population per unit area is very high.
It is most suitable for oil seeds and other cereal and vegetable crops
 Water saving
 Closer control of water application convenient for giving light and frequent
Irrigation and higher water application efficiency
 Increase in yield
 Mobility of system
 May also be used for undulating area
 Saves land as no bunds etc. are required
 Influences greater conducive micro-climate
 Areas located at a higher elevation than the source can be irrigated
 Possibility of using soluble fertilizers and chemical
 Less problem of clogging of sprinkler nozzles due to sediment laden water

Crop response to sprinkler

The trials conducted in different parts of the country revealed water saving due to
sprinkler system varies from 16 to 70 % over the traditional method with yield
increase from 3 to 57 % in different crops and agro climatic conditions. (Table .1)
Response of different crops to sprinkler irrigation
General classification of different types of sprinkler systems
Sprinkler systems are classified into the following two major types on the basis of the
arrangement for spraying irrigation water.
1. Rotating head or revolving sprinkler system.
2. Perforated pipe system

1) Rotating head:
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 90 0, 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.

Fig .1 Example of a few rotating type sprinkler irrigation systems

2) Perforated pipe system:
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). The application rate ranges from 1.25 to 5 cm per hour for
various pressure and spacing. Based on the portability, sprinkler systems are classified
into the following types:
(i) Portable system : A portable system has portable main lines, laterals and
pumping plant

Fig .2 Fully portable sprinkler irrigation system

(ii) Semi portable system: A semi portable system is similar to a portable system
except that the location of water source and pumping plant is fixed.

(iii) Semi permanent system: A semi permanent system has portable lateral lines,
permanent main lines and sub mains and a stationery water source and pumping plant.

(iv) Solid set system: A solid set system has enough laterals to eliminate their
movement. The laterals are positions in the field early in the crop season and remain
for the season.

(v) Permanent system: A fully permanent system consists of permanently laid mains,
sub mains and laterals and a stationery water source and pumping plant.

Components of sprinkler irrigation system

The components of portable sprinkler system are shown through fig .3. A sprinkler
system usually consists of the following components
(i) A pump unit
(ii) Tubing's- main/sub mains and laterals
(iii) Couplers
(iv) Sprinkler head
(v) Other accessories such as valves, bends, plugs and risers
 Fig .3 Component of a portable sprinkler irrigation system

(i) Pumping Unit: Sprinkler irrigation systems distribute water by spraying it over the
fields. The water is pumped under pressure to the fields. The pressure forces the water
through sprinklers or through perforations or nozzles in pipelines and then forms a
spray. A high speed centrifugal or turbine pump can be used for operating sprinkler
irrigation for individual fields. Centrifugal pump is used when the distance from the
pump inlet to the water surface is less than eight meters. For pumping water from
deep wells or more than eight meters, a turbine pump is suggested. The driving unit
may be either an electric motor or an internal combustion engine.

(ii)Tubing's: Mains/sub mains and laterals: The tubing's consist of mainline, sub
mains and laterals. Main line conveys water from the source and distributes it to the
sub mains. The sub mains convey water to the laterals which in turn supply water to
the sprinklers. Aluminum or PVC pipes are generally used for portable systems, while
steel pipes are usually used for center-pivot laterals. Asbestos, cement, PVC and
wrapped steel are usually used for buried laterals and main lines

(iii) Couplers: Couplers are used for connecting two pipes and uncoupling quickly
and easily. Essentially a coupler should provide
(a) a reuse and flexible connection
(b) not leak at the joint
(c) be simple and easy to couple and uncouple
(d) be light, non-corrosive, durable

(iv) Sprinkler Head: Sprinkler head distribute water

uniformly over the field without runoff or excessive
loss due to deep percolation. Different types
of sprinklers are available. They are either rotating
or fixed type. The rotating type can be adapted for
a wide range of application rates and spacing.
They are effective with pressure of about 10 to 70 m head
at the sprinkler. Pressures ranging from 16 to 40 m
head are considered the most practical for most farmers
Fig.4 Sprinkler head
Fixed head sprinklers are commonly used to irrigate small lawns and gardens.
Perforated lateral lines are sometimes used as sprinklers. They require less pressure
than rotating sprinklers. They release more water per unit area than rotating
sprinklers. Hence fixed head sprinklers are adaptable for soils with high intake rate.

(v) Fittings and accessories: The following are some of the important fittings and
accessories used in sprinkler system.
(1) Water meters: It is used to measure the volume of water delivered. This is
necessary to operate the system to give the required quantity of water.
(2) Flange, couplings and nipple used for proper connection to the pump, suction and
delivery.
(3) Pressure gauge: It is necessary to know whether the sprinkler system is working
with desired pressure to ensure application uniformity.
(4) Bend, tees, reducers, elbows, hydrants, butterfly valve and plugs.
(5) Fertilizer applicator: Soluble chemical fertilizers can be injected into the sprinkler
system and applied to the crop. The equipment for fertilizer application is relatively
cheap and simple and can be fabricated locally. The fertilizer applicator consists of a
sealed fertilizer tank with necessary tubing's and connections. A venturi injector can
be arranged in the main line, which creates the differential pressure suction and allows
the fertilizer solution to flow in the main water line

Fig 2.5 Different sprinkler pipes and fittings

General rules for sprinkler system design
 Main should be laid up and down hill
• Lateral should be laid across the slope or nearly on the contour
• For multiple lateral operation, lateral pipe sizes should not be more than two
diameter
• Water supply source should be nearest to the center of the area
 Layout should facilitate and minimize lateral movement during the season
• Booster pump should be considered where small portion of field would require high
pressure at the pump
• Layout should be modified to apply different rates and amounts of water where soils
are greatly different in the design area.

Fig

.6 Layout of sprinkler irrigation system

Selecting the most appropriate sprinkler systems

While selecting a sprinkler system, the most important physical parameters to be
considered are:
1. The crop or crops to be cultivated.
2. The shape and size (acres) of the field.
3. The topography of the field.
4. The amount of time and labor required to operate the system.

Selecting sprinkler system capacity

A sprinkler system must be designed to apply water uniformly without runoff or
erosion. The application rate of the sprinkler system must be matched to the
infiltration rate of the most restrictive soil in the field. If the application rate exceeds
the soil intake rate, the water will run off the field or relocate within the field resulting
in over and under watered areas.
The sprinkler system capacity is the flow rate needed to adequately irrigate an area
and is expressed in liters per minute per acre. The system capacity depends upon on
the: Peak crop water requirements during the growing season; effective crop rooting
depth; texture and infiltration rate of the soil; the available water holding capacity of
the soil; pumping capacity of the well or wells (if wells are the water source).

Constraints in application of sprinkler irrigation

(i) Uneven water distribution due to high winds
(ii) Evaporation loss when operating under high temperatures
(iii) Highly impermeable soils are not suitable
(iv) Initial cost is high
(v) Proper design
(vi) Lack of Package of practices
(vii) Lack of awareness
(viii) Lack of social concern to save natural resources
(ix) High water pressure required in sprinkler (>2.5kg/cm2)
(x) Difficulty in irrigation during wind in sprinkler

Operation and Maintenance of Sprinkler Systems

Proper design of a sprinkler system does not in itself ensure success. It should be
ensured that the prime mover and the pump are in alignment, particularly in the case
of tractor-driven pumps. For these the drive shaft as well as the pump shaft should lie
at nearly the same height to prevent too great an angle on the universal shaft.
While laying the main and lateral pipes, always begin laying at the pump. This
necessarily gives the correct connection of all quick coupling pipes. While joining
couplings, it is ensured that both the couplings and the rubber seal rings are clean.

In starting the sprinkler system, the motor or engine is started with the valves closed.
The pump must attain the pressure stated on type-plate or otherwise there is a fault in
the suction line. After the pump reaches the regulation pressure, the delivery valve is
opened slowly. Similarly, the delivery valve is closed after stopping the power unit.

The pipes and sprinkler-lines are shifted as required after stopping. Dismantling of the
installation takes place in the reverse order to the assembly described above.

Maintenance
General principles regarding the maintenance of the pipes and fittings and sprinkler
heads are given below:

1. Pipes and fittings

The pipes and fittings require virtually no maintenance but attention must be given to
the following procedures:
(a) Occasionally clean any dirt or sand out of the groove in the coupler in which the
rubber sealing ring fits. Any accumulation of dirt or sand will affect the performance
of the rubber sealing ring.
(b) Keep all nuts and bolts tight.
(c) Do not lay pipes on new damp concrete or on piles of fertilizer. Do not lay
fertilizer sacks on the pipe.
2. Sprinkler heads
The sprinkler heads should be given the following attention:
(a) When moving the sprinkler lines, make sure that the sprinklers are not damaged or
pushed into the soil.
(b) Do not apply oil, grease or any lubricant to the sprinklers. They are water
lubricated and using oil, grease or any other lubricant may stop them from working.
(c) Sprinklers usually have a sealed bearing and at the bottom of the bearing there are
washers. Usually it is the washers that wear and not the more expensive metal parts.
Check the washers for wear once a season or every six months which is especially
important where water is sandy. Replace the washers if worn.
(d) After several season's operation the swing arm spring may need tightening. This is
done by pulling out the spring end at the top and rebinding it. This will increase the
spring tension.
In general, check all equipment at the end of the season and make any repairs and
adjustments and order the spare parts immediately so that the equipment is in perfect
condition to start in the next season.

Storage
The following points are to be observed while storing the sprinkler equipment during
the off season:
(a) Remove the sprinklers and store in a cool, dry place.
(b) Remove the rubber sealing rings from the couplers and fittings and store them in a
cool, dark place.
(c) The pipes can be stored outdoors in which case they should be placed in racks with
one end higher than the other. Do not store pipes along with fertilizer.
(d) Disconnect the suction and delivery pipe-work from the pump and pour in a small
quantity of medium grade oil. Rotate the pump for a few minutes. Blank the suction
and delivery branches. This will prevent the pump from rusting. Grease the shaft.
(e) Protect the electric motor from the ingress of dust, dampness and rodents.

Sprinkler use

Most irrigation sprinklers are used as part of a sprinkler system, consisting of

various plumbing parts, piping and control equipment. Piping is connected to the
water source via plumbing fittings and the control system opens and closes
valves to provide water on a schedule. The control provided varies depending on
the equipment used; some systems are fully automated and even compensate for
rain, runoff and evaporation, while others require much more user attention for
the same effectiveness.
Outdoor sprinkler systems are sometimes used as a deterrent against homeless people.
For example, the city of Los Angeles installed an elaborate overhead sprinkler system
in a downtown park along lower Fifth Street. This sprinkler system was programmed
to drench unsuspecting sleepers at random times during the night. Local businessmen
soon copied this system in an effort to drive homeless people away from public
sidewalks adjacent to their businesses

Trouble Shooting
The following are the general guidelines to identify and remove the common troubles
in the sprinkler systems:
1. Pump does not prime or develop pressure
(a) Check that the suction lift is within the limits. If not, get the pump closer to the
water.
(b) Check the suction pipeline and all connections for air leaks. All connections and
flanges should be air tight.
(c) Check that the strainer on the foot valve is not blocked.
(d) Check that the flap in the foot valve is free to open fully.
(e) Check the pump gland (s) for air leaks. If air leaks are suspected tighten the gland
(s) gently. If necessary repack the gland (s) using a thick grease to seal the gland
satisfactorily.
(f) Check that the gate valve on the delivery pipe is fully closed during priming and
opens fully when the pump is running.

2. Sprinklers do not turn

(a) Check pressure.
(b) Check that the nozzle is not blocked. Preferably unscrew the nozzle or use a small
soft piece of wood to clear the blockage. Do not use a piece of wire or metal as this
may damage the nozzle.
(c) Check the condition of washers at the bottom of the bearing and replace them if
worn or damaged.
(d) Check that the swing arm moves freely and that the spoon which. moves into the
water stream is not bent by comparing it with a sprinkler which is operating correctly.
(e) Adjust the swing arm spring tension~ Usually it should not be necessary to pull up
the spring by more than about 6 mm.
3. Leakage from coupler or fittings
The sealing rings in the couplers and fittings are usually designed to drain the water
from the pipes when the pressure is turned off. This ensures that the pipes are
automatically emptied and ready to be moved. With full pressure in the system the
couplers and fittings will be effectively leak-free. If, however, there is a leakage,
check the following:
(a) There is no accumulation of dirt or sand in the groove in the coupler in which the
sealing ring fits. Clean out any dirt or sand and refit the sealing ring.
(b) The end of the pipe going inside the coupler is smooth, clean and not distorted.
(c) In the case of fittings such as bends, tees and reducers ensure that the fitting has
been properly connected into the coupler.

Unit Cost of Sprinkler Systems

Different components required for a sprinkler irrigation system to irrigate 1 ha to 4 ha
area and their cost has been estimated and given in Table .3
Table .3 Unit Cost of Sprinkler Systems