The document discusses the hydraulic design of sprinkler irrigation systems, including selecting sprinkler types and spacing based on manufacturer specifications to achieve uniform water coverage, calculating sprinkler discharge rates and wetted area, and considering factors such as soil characteristics, crop water requirements, and wind conditions when designing the pipe network and layout of mainlines, submains, and laterals. The goal is to provide sufficient water flow and uniform distribution while maintaining pressure throughout the system.

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Sprinkler Irrigation System:
Hydraulic Design of Sprinkler Irrigation System
Speaker
Dr. Jitendra Sinha
Associate Professor
Department of Soil and Water Engineering,
SVCAETRS, FAE, IGKV, Raipur
jsvenusmars@gmail.com
7000633581

2. Sprinkler selection and spacing
• The actual selection of the sprinkler is based largely
upon design information furnished by the manufacturer.
• The choice depends mainly on the diameter of coverage
required, pressure available and sprinkler discharge.
• The tables presented before may be taken as guidelines
during selection.
• The best combination of an individual sprinkler spacing
and lateral moves, suiting the application rate for the soil
and wind condition should be selected.
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3. 3

4. 4

5. 5
Can you solve this?
Would like to know the answer…..

6. 6
16 16
Main Line
18 m
15
12 m

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8. 8

9. 9

10. 400 m
10
400 m
L1
186 m
L2
186 m

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12. 12

13. 13
100 cm60 cm
9.5 cm
5.7 cm

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15. Application Uniformity
• Distribution uniformity (DU)
– dLQ = average low-quarter depth of water received
– dz = average depth applied
• Popular parameter for surface irrigation
systems in particular







zd
d
DU
LQ
100

16. Application Uniformity Cont’d…
• Christiansen’s Coefficient of Uniformity (CU)
– n = number of observations (each representing the same
size area)
– dz = average depth for all observations
– di = depth for observation i
• Popular parameter for sprinkler and micro-irrigation
systems in particular





 
 
n
i z
iz
nd
dd
CU
1
1100

17. Efficiencies and Uniformities
• Application efficiency (Ea)
– dn = net irrigation depth
– dg = gross irrigation depth
– fraction or percentage
• Water losses
– Evaporation
– Drift
– Runoff
– Deep percolation
E
d
d
a
n
g


18. Field plot Depth of water application (cm)
Akbar’s 5 4 3 2 1
Birbal’s 4 3 3 3 2
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Akbar and Birbal irrigated their field plot (equal in area) with
same limited quantity of water. After an hour of irrigation,
the depth of water applied at different points on the field
was measured. Work out the Coefficient of Uniformity of the
two systems from the following observation and compare
wisdom of Akbar and Birbal.

21. Planning Considerations
 Field Size
 Available water supply
 Management ability
 Labor availability
 Crops to be grown
 Soils characteristics
 Intake Rate
 Water holding capacity

22. Center Pivot: Planning Considerations
 Field Size – General needs large areas
 Available water supply – meets crop needs
 Management ability – Can manage multiple systems
 Labor availability – Low labor requirements
 Crops to be grown – must clear canopy
 Soils characteristics
 Intake Rate - runoff potential at outer end
 Water holding capacity – can apply small depths

23. Linear Move: Planning Considerations
 Field Size – General needs large rectangular areas
 Available water supply – meets crop needs
 Management ability – Can manage multiple systems
 Labor availability – Labor required to move hose
 Crops to be grown – must clear canopy
 Soils characteristics
 Intake Rate - Application rate constant along lateral
 Water holding capacity – can apply small depths

24. Solid set: Planning Considerations
 Field Size – Can be designed for irregular shapes
 Available water supply – meets crop needs
 Management ability – Can manage multiple systems
 Labor availability – Minimum Labor unless hand move
 Crops to be grown – Generally not a limitation
 Soils characteristics
 Intake Rate - Application rate function of spacing
 Water holding capacity – can apply small depths

25. Hydraulic design of sprinkler system
• To obtain uniform irrigation profile
• The desired rate of application
• The break up of sprinkler drops necessary to
minimize structural deterioration of the soil surface
• The efficiency desired to reduce the energy
requirement in operating the system
• To maximize the area of coverage
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26. Discharge of sprinkler nozzle
• q = C a 2𝑔ℎ (Toricelli)
• q = nozzle discharge, m3/s
• a = cross sectional area of nozzle or orifice, m2
• h = pressure head at the nozzle, m
• g = acceleration due to gravity, m/sec2
• c = coefficient of discharge which is function
of friction and contraction losses (0.95 to 0.96
for good nozzles)
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27. Water spread of sprinkler
• R = 1.35 𝑑ℎ (Cavazza, Pillsburry)
• R = radius of wetted area covered by sprinkler,
m
• d = diameter of nozzle, m
• h = pressure head at the nozzle, m
• Maximum coverage is attained when the jet
emerges from the sprinkler at an angle of 30o
to 32o above the horizontal.
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28. Break up of jets
• Pd = h/(10q)0.4
• Pd = index for jet break-up
• h = pressure head at the nozzle, m
• q = sprinkler discharge, lps
• If Pd is greater than 2, the condition of drop
size is good, if 4; the condition of drop size is
best, if greater than 4 the pressure is being
wasted
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29. Rate of application
• Ra = q/360 A
• Ra = water application rate, cm/h
• q = sprinkler discharge, lps
• A = wetted area sprinkler, m2
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30. Design of Sprinkler system
The following should be considered for design:
• Area of land
• Consumptive use of crop
• Water holding capacity
• Root zone depth
• Effective rainfall
• Water application efficiency
• Antecedent moisture content
• Net irrigation requirement
• Gross irrigation requirement
• Irrigation frequency
• Maximum time needed to apply (hrs)

31. Design of Sprinkler Irrigation System
• Objectives and Procedures
• Provide Sufficient Flow Capacity to meet the
Irrigation Demand
• Ensure that the Least Irrigated Plant receives
adequate Water
• Ensure Uniform Distribution of Water.

32. Design Steps
• Determine Irrigation Water Requirements and
Irrigation Schedule
• Determine Type and Spacing of Sprinklers
• Prepare Layout of Mainline, Submains and
Laterals
• Design Pipework and select Valves and Fittings
• Determine Pumping Requirements.

33. Choice of Sprinkler System
• Consider:
• Application rate or precipitation rate
• Uniformity of Application: Use UC
• Drop Size Distribution and
• Cost

34. Sprinkler Application Rate
• Must be Less than Intake Rates
Soil Texture Max. Appln. Rates
(mm/hr.)
Coarse Sand 20 to 40
Fine Sand 12 to 25
Sandy Loam 12
Silt Loam 10
Clay Loam/Clay 5 to 8

35. Effects of Wind
• In case of Wind:
• Reduce the spacing between Sprinklers
• Allign Sprinkler Laterals across prevailing wind
directions
• Build Extra Capacity
• Select Rotary Sprinklers with a low trajectory
angle.

36. Pipework Design
• This involves the Selection of Pipe Sizes to
ensure that adequate water can be distributed
as uniformly as possible throughout the
system
• Pressure variations in the system are kept as
low as possible as any changes in pressure
may affect the discharge at the sprinklers

37. Reference
• Irrigation : Theory and Practice by A. M. Michael
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