Drip Irrigation System 03

1. DRIP
IRRIGATION
SYSTEM
Dr. G.K. Nigam
Ph.D. (Soil & Water Engg.)

2. 2
Design of Drip
Irrigation System

3. 3
General information required to design a Drip Irrigation
System
⮚ Source of Irrigation water
⮚ Crops to be grown
⮚ Topographic conditions
⮚ Texture of soil
⮚ Climatic data
Steps of drip irrigation design
⮚ Number of laterals and drippers
⮚ In Orchards and Vegetable crops
⮚ In close growing field crops
⮚ Number of fittings and accessories
⮚ Capacity of Main pipe
⮚ Capacity of Sub-main pipe
⮚ Capacity of Lateral pipes

4. 4
Steps of drip irrigation design
⮚ Number of laterals and drippers
⮚ In Orchards and Vegetable crops
⮚ In close growing field crops
⮚ Number of fittings and accessories
⮚ Capacity of Main pipe
⮚ Capacity of Sub-main pipe
⮚ Capacity of Lateral pipes
⮚ Diameter of Lateral pipe
⮚ Diameter of Main pipe
⮚ Diameter of Sub-main pipe
⮚ Filters
⮚ Fertilizer applicators
⮚ Size of pumping unit
⮚ Total cost of drip system

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6. 6
Determine water requirements to be
met with a Drip irrigation system.
Select and design emitters
Determine capacity requirements
of the Drip irrigation system
Determine appropriate filter
system for site conditions and
selected emitter
Determine required sizes of
mainline pipe, manifold, and
lateral lines
Check pipe sizes for power
economy.
Determine maximum and
minimum operating flow
rates and pressures
Select pump and power unit
for maximum operating
efficiency within the range of
operating conditions.
Determine requirements for
chemical fertilizer equipment.
Prepare drawings, specifications,
cost estimates, schedules, and
instructions for proper layout,
operation and
maintenance.
Flow chart of designing Drop Irrigation system

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8. 8
WETTING
PATTERN

9. 9
Wetting patterns for sandy soils with high and low
discharge rates

10. 10
Wetting patterns for clay soils with high and low
discharge rates

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17. Irrigation Requirement
Evapotranspiration of crop (mm per day per plant)
ETc = (ET0) × Crop coefficient (Kc) - Rainfall
Net volume of water required by plant ( litre per day)
V = IR × A × 1000
Where,
ET0 = Reference Evapotranspiration (mm day-1 )
Kc = Crop coefficient,
V = Vol. of water applied (l day-1)
IR = Required irrigation (m)
A = Area of one plant (m2)
Source: (Tiwari et al.)
17

18. Observations on wetted depth and width of soil
Observations on depth and width of wetted soil after 30, 60, 90,
120, 150 and 180 minutes of water application were recorded at
0.7 and 1.2 kgcm-2 .
Hydraulic performance of drip irrigation system
Wetted soil depth Wetting patterns on soil Wetted soil width
18

19. 19
Capacity of drip system
Factor affects the drip system capacity
❖Irrigation water requirement
❖Daily operating hours
❖Irrigation interval
❖Water application efficiency
• Drip irrigation system is generally not recommended to
operate for more than 1.5 - 2.0 hours at a stretch to avoid
losses of water through leaching
• Irrigation interval generally is not kept more than three
days to avoid moisture stress to plants.

20. 20
Equation to estimate Capacity of Drip System
Q = A * CU * T */(ηa * t)
where,
Q = Capacity of drip system, lph
A = Total cultivated area, m2
T = Irrigation interval, days
ηa =Water application efficiency (in fraction)
t = Duration of each irrigation, h
Discharge required per plant (Qp) can simply be estimated by
dividing the drip capacity (Q) by the number of plants (n) in the area.
Qp = Q/n

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Length of main, sub-main and lateral lines
Length of main, sub-main and lateral lines can be calculated with
the help of length, width and total number of equal sized blocks in a
field.
Length of main line = width of block (if number of block i.e. NB =
1, in small fields)
Total length of main line (Lm) = (NB-1) x width of block (if NB>1)
Length of submain line (Ls) = width of block (Bw)
No submain if NB = 1
Total length of submain = Ls X NB
Length of lateral line (LL)= Length of block (BL)
Total length of lateral = LL X NB X NR
Where, NR = Number of plant row per block

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27. Measurement of discharge from emitters
Emitters having discharge capacity i.e. 2.4 lph were
tested at different operating pressure i.e. 0.7, 1.0, 1.2
and 1.5 kg /cm² and these pressures are maintained by
using control valve at head control unit.
Pressure measurement of different component of drip
irrigation system
Discharge measurement
Pressure on main line Pressure on lateral line 27

28. Coefficient of manufacturer’s variation
Where,
S = is standard deviation of flow and
qa = is the mean flow for a sampled number of emitters of the same type tested at a fixed
pressure lh-1
Uniformity coefficient (Us)
Statistical uniformity coefficient given by the equation ( Bralts and Kesner, 1982)
US = 100(1- Vq) = 100 (1- Sq / qa)
Where,
Vq = coefficient of variation
S q = is standard deviation of flow and
qa = average of emitter discharge, lh-1
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29. (II) Method: Emitter flow variation (Wu and Gitlin, 1974)
Where,
Qvar = emitter flow variation in percentage
Qmin = minimum emitter discharge rate in the system, lh-1
Qmax = design emitter discharge rate, lh-1
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Qvar

30. Distribution efficiency
Where,
Ed = distribution efficiency
Δqa = average absolute deviation of each emitter
flow from the mean emitter flow lh-1
qm = mean emitter flow rate lh-1
Application efficiency
Where,
Ea = application efficiency, %
Qmin = minimum emitter flow rate, lh-1
Qavg = average emitter flow lh-1
Drip Irrigation Efficiency
(Source: “Principal of Drip Irrigation System” by M. S. Mane, B. L. Ayare, S. S. Magar)
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31. Hydraulic performance of drip irrigation system
Behavior of wetted soil width and depth
Wetting front advance at different times for clay loam soil for 2.4 lh-1
dripper at 0.7 kgcm-2 pressure
Root zone
Of crop
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32. Wetting front advance at different times for clay loam
soil for 2.4 lh-1 dripper at 1.2 kgcm-2 pressure
Root
zone
Of
crop
32
45 40 35 30 25 20 15 10 5 0 5 10 15 20 25 30 35 40 45051015202530354045
Horizontal Wetting Front Advance, cm
VerticalWettingFrontAdvance,cm
30 min
60 min
90 min
120 min
150 min
180 min
Wetting front advance at different times for clay
loam soil for 2.4 lh-1 dripper at 1.2 kgcm-2 pressure

33. S.NO. Pressure (kgcm-2) Average emitter flow rate (lh-1 )
1 0.7 1.63
2 1 1.94
3 1.2 2.1
4 1.5 2.30
Observation of discharge of drip irrigation system with
different pressure
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34. Operating
pressure 0.7 (kgcm-2) 1(kgcm-2) 1.2 (kgcm-2) 1.5 (kgcm-2)
Uniformity
coefficient(%) 89.38 94.89 96.46 97.34
Classification Good Excellent Excellent Excellent
Uniformity coefficient
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35. Operating
Pressure 0.7 (kgcm-2) 1 (kgcm-2) 1.2 (kgcm-2) 1.5 (kgcm-2)
Distribution
efficiency (%)
89.39 94.9 96.04 97.34
Distribution efficiency
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36. Operating
Pressure 0.7 (kgcm-2) 1 (kgcm-2) 1.2 (kgcm-2) 1.5 (kgcm-2)
Application
efficiency (%)
80.52 89.59 94.43 95.96
Application efficiency
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