Part B3: Irrigation

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Part B3 Irrigation B3.1 Irrigation techniques
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B3.2 Irrigation techniquesTopics

• Surface irrigation
• Basin irrigation, border irrigation, furrow
  irrigation
• Rainwater harvesting
• Bunds, microcatchments,
• Modern irrigation techniques
• Spray irrigation, micro irrigation

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B3.2.1 Irrigation techniquesSurface irrigation
Flow
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B3.2.1 Irrigation techniques Surface irrigation
Flow
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B3.2.1 Irrigation techniquesSurface irrigation
Inlet arrangements
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B3.2.1 Irrigation techniquesSurface irrigation
Inlet arrangements
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B3.2.1 Irrigation techniquesSurface irrigation
Inlet arrangements
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B3.1.4 Fundamentals of irrigation Surface
irrigation The quarter time rule

Tf Time to reach the opposite end of the
field (hr) Ta Application time (hr)
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B3.2.1 Irrigation techniquesSurface irrigation
Basin irrigation
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B3.2.1 Irrigation techniques Surface irrigation
Flow
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B3.2.1 Irrigation techniquesSurface irrigation
Basin irrigation
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B3.2.1 Irrigation techniquesSurface irrigation
Basin irrigation Scaling
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B3.1.4 Fundamentals of irrigation Surface
irrigation Basin irrigation Scaling
Stream size (l/s) Sand Sandy loam Clay loam Clay
15 0.01 0.03 0.06 0.10
30 0.02 0.06 0.12 0.20
60 0.04 0.12 0.24 0.40
90 0.06 0.18 0.36 0.60
120 0.08 0.24 0.48 0.80
150 0.10 0.30 0.60 1.00
180 0.12 0.36 0.72 1.20
210 0.14 0.42 0.84 1.40
240 0.16 0.48 0.96 1.60
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B3.2.1 Irrigation techniquesSurface irrigation
Basin irrigation Problems
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B3.2.1 Irrigation techniquesSurface irrigation
Basin irrigation Terracing
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B3.2.1 Irrigation techniquesSurface irrigation
Border irrigation
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B3.2.1 Irrigation techniquesSurface irrigation
Border irrigation
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B3.2.1 Irrigation techniquesSurface irrigation
Border irrigation
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B3.2.1 Irrigation techniquesSurface irrigation
Border irrigation Scaling
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B3.2.1 Irrigation techniques Surface irrigation
Border irrigation Scaling
Soil type Irrigation depth (mm) Slope () Width (m) Length (m) Unit stream (l/s/m)
Sand 100 0.2 12-30 60-100 10-15
Sand 100 0.4 10-12 60-100 8-10
Sand 100 0.8 5-10 75 5-7
Sand 150 0.2 15-30 90-300 4-6
Sand 150 0.4 10-12 90-180 3-5
Sand 150 0.8 5-10 90 2-4
Sand 200 0.2 15-30 350 3-6
Sand 200 0.4 10-12 180-300 2-4
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B3.2.1 Irrigation techniques Surface irrigation
Border irrigation Scaling
Soil type Humid areas Humid areas Arid areas Arid areas
Soil type Bare soil Good crop cover Bare soil Good crop cover
Sand 0.3 1.0 1.0 2.0
Clay 0.5 2.0 2.0 5.0
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B3.2.1 Irrigation techniquesSurface irrigation
Border irrigation Problems
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B3.2.1 Irrigation techniquesSurface irrigation
Border irrigation Problems
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B3.2.1 Irrigation techniquesSurface irrigation
Furrow irrigation
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B3.2.1 Irrigation techniquesSurface irrigation
Furrow irrigation
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B3.2.1 Irrigation techniquesSurface irrigation
Furrow irrigation
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B3.2.1 Irrigation techniquesSurface irrigation
Furrow irrigation
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B3.2.1 Irrigation techniquesSurface irrigation
Furrow irrigation
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B3.2.1 Irrigation techniquesSurface irrigation
Furrow irrigation Infiltration
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B3.2.1 Irrigation techniquesSurface irrigation
Furrow irrigation Scaling
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B3.2.1 Irrigation techniquesSurface irrigation
Furrow irrigation Scaling
Slope () Max stream size (l/s) Average irrigation depth (mm) Average irrigation depth (mm) Average irrigation depth (mm) Average irrigation depth (mm) Average irrigation depth (mm) Average irrigation depth (mm) Average irrigation depth (mm) Average irrigation depth (mm)
Slope () Max stream size (l/s) Clay Clay Loam Loam Loam Sand Sand Sand
Slope () Max stream size (l/s) 75 150 50 100 150 50 75 100
0.05 3.0 300 400 120 270 400 60 90 150
0.1 3.0 340 440 180 340 440 90 120 190
0.2 2.5 370 470 220 370 470 120 190 250
0.3 2.0 400 500 280 400 500 150 220 280
0.5 1.2 400 500 280 370 470 120 190 250
1.0 0.6 280 400 250 300 370 90 150 220
1.5 0.5 250 340 220 280 340 80 120 190
2.0 0.3 220 270 180 250 300 60 90 150
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B3.2.1 Irrigation techniquesSurface irrigation
Furrow irrigation
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B3.2.1 Irrigation techniquesSurface irrigation
Furrow irrigation problems
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B3.2.2 Irrigation techniquesRainwater harvesting

• The collection and concentration of runoff
• Sits between rain-fed agriculture and traditional
  irrigation
• Can produce a crop where none is possible with
  simple rain catchment
• Usually in arid and semi-arid areas but also
  suited to semi tropical
• Rainwater is purer than ground or surface water
• salinity

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B3.2.2 Irrigation techniquesRainwater harvesting
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B3.2.2 Irrigation techniquesRainwater harvesting
Rain fed agriculture
Rainwater harvesting
Irrigated agriculture
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B3.2.2 Irrigation techniquesRainwater
harvesting limitations

• Climatic fluctuations
• Yields cannot be guaranteed
• Potential up and downstream conflict (but less
  than traditional irrigation
• Some scientific uncertainty
• Large schemes difficult to implement

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B3.2.2 Irrigation techniquesRainwater harvesting
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B3.2.2 Irrigation techniquesRainwater
harvesting Catchment cultivated area ratio
(CCa)

C Catchment Ca Cultivated area ETcr Crop
evapotranspiration P Design rainfall k
Runoff coefficient ? Efficiency
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B3.2.2 Irrigation techniquesRainwater
harvesting Efficiency
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B3.2.2 Irrigation techniquesRainwater
harvesting Design Rainfall curve
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B3.2.2 Irrigation techniquesRainwater
harvesting Design Rainfall Exceedance table
Jan Feb. Mar Apr May Jun Jul Aug Sep Oct Nov Dec
10 200 60 150 250 250 240 200 200 170 370 390 300
20 170 40 75 220 200 200 170 160 150 340 340 240
30 160 18 65 210 190 190 160 150 145 310 310 190
40 155 11 60 200 140 140 140 120 140 300 300 160
50 120 7 55 190 85 110 120 110 120 290 290 110
60 90 5 47 170 80 105 105 96 100 270 270 105
70 60 1 40 150 74 100 100 90 90 250 250 90
80 18 0 18 140 65 95 90 80 55 200 200 55
90 16 0 4 90 60 90 40 72 40 190 190 40
99 12 0 0 60 0 60 0 60 50 18 140 18
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B3.2.2 Irrigation techniquesRainwater
harvesting Microcatchments

• Small (thus the name) 1-1000m2
• Catchment and cropping areas adjacent
• Crops are usually a single tree/catchment or
  small annual crop
• No overflow
• Small area ratio (11 101)
• Tend to be in series of units
• Efficiency 0.5-0.6

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B3.2.2 Irrigation techniquesRainwater
harvesting Microcatchments
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B3.2.2 Irrigation techniquesRainwater
harvesting Microcatchments Negarims
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B3.2.2 Irrigation techniquesRainwater
harvesting Microcatchments Negarims
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B3.2.2 Irrigation techniquesRainwater
harvesting Microcatchments Negarims
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B3.2.2 Irrigation techniquesRainwater
harvesting Microcatchments Semi circular bunds
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B3.2.2 Irrigation techniquesRainwater
harvesting Microcatchments Semi circular bunds
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B3.2.2 Irrigation techniquesRainwater
harvesting Microcatchments Semi circular bunds
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B3.2.2 Irrigation techniquesRainwater
harvesting Microcatchments Semi circular bunds
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B3.2.2 Irrigation techniquesRainwater
harvesting Microcatchments Contour bunds
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B3.2.2 Irrigation techniquesRainwater
harvesting Microcatchments Contour bunds
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B3.2.2 Irrigation techniquesRainwater
harvesting Macrocatchments

• Big 750-10,000m2
• Used for all types of crops
• Often includes overflow structures
• larger area ratio (101 1001)
• Efficiency 0.2-0.4

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B3.2.2 Irrigation techniquesRainwater
harvesting Macrocatchments Stone bunds
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B3.2.2 Irrigation techniquesRainwater
harvesting Macrocatchments Stone bunds
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B3.2.2 Irrigation techniquesRainwater
harvesting Macrocatchments Stone bunds
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B3.2.2 Irrigation techniquesRainwater
harvesting Macrocatchments Hillside conduits
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B3.2.2 Irrigation techniquesRainwater
harvesting Macrocatchments Hillside conduits
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B3.2.2 Irrigation techniquesRainwater
harvesting Macrocatchments Hillside conduits
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B3.2.2 Irrigation techniquesRainwater
harvesting Macrocatchments Hillside conduits
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B3.2.2 Irrigation techniquesRainwater
harvesting Floodwater harvesting

• Can be diverted to conventional-style irrigation
  or microcatchments
• Variable size Ha km2
• Used for all types of crops
• Variable area ratio (11 10,0001)

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B3.2.2 Irrigation techniquesRainwater
harvesting Floodwater harvesting (water
spreading)
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B3.2.2 Irrigation techniquesRainwater
harvesting Floodwater harvesting (water
spreading)