AGE 506 IRRIGATION ENGINEERING

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AGE 506 IRRIGATION ENGINEERING

• Course Lecturer Dr J.K. Adewumi
• Dept. of Agricultural Engineering
• UNAAB. Nigeria

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Methods of Irrigation

• A. Surface Irrigation
• Wild flooding
• Border strip
• Check Basin
• Furrow
• Sub- Irrigation
• Natural sub-irrigation (Advantages
  disadvantages)
• Artificial sub-irrigation (Advantages
  disadvantages)
• Overhead Irrigation
• Rotating head systems
• Perforated pipe system
• Furrow irrigation
• Border Irrigation
• Level Border
• Graded Border

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Water Measurement in Open channel

• Water measurement in pipes
• Volume
• Velocity
• Orifices
• Basin Flow Equations
• Hydraulic Radius
• Continuity Equation
• Darcy-Weibach Equation
• Bernoullis Equation

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Measurement of Irrigation Water

• Bucket and watch method
• Float method
• Flow from a vertical pipe
• Flow from a horizontal pipe
• Discharge from siphon tubes

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Frequency and Amount of Irrigation

• Methods of Frequency
• Meteorological Method for determining CU or ETp
  for the plant
• Blaney Criddle method
• Plant Index method
• (i) Crop itself
• (ii) indicator Plant
• (iii) change in leave colour
• (iv) Physiological Index
• Soil Index method
• (i) Moisture content
• (ii) Soil potential by tensiometer
• Methods of determining amount of irrigation
• Tensiometer
• C.U.
• Available water moisture

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Irrigation Efficiencies

• Reservoir Storage Efficiency
• Er Ws/Wso X 100, Ws amount of water
  directed, Wso amount of water stored
• Water conveyance Efficiency
• Ec Wf/Wr X 100, Wf amount of water delivered
  into farm, Wr water diverted from reservoir
• Water application Efficiency
• Ea Wst/Wf X 100 Where Wst water stored in
  root zone ,
• Overall Irrigation Efficiency
• Ei Er X Ec X Ea (100) or Ei Er/Wd where Wd
  water stored or diverted for irrigation
• Water distribution Efficiency
• Ed 1 y where d ave. depth of water stored
  along run during irrigation, y ave. numerical
  deviation from d
• d

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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 dg (hrs)

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Quality of irrigation water

• Depends on amount and kind of salt present
• Total salt concentration
• Relative proportion
• Bicarbonate and boron contents
• Suitability of irrigation water can be expressed
  as SIW f(QSPCD)
• Where Q quality of irrigation water
• S soil type
• P salt tolerance characteristics of
  the plant
• C climate
• D drainage characteristics of the soil

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Drainage of Agricultural land

• Effects of poor drainage on plants and soil
• Reduces aeration in soil
• Water-logging
• Anaerobic decomposition
• Temperature fluctuation in soil

• Factors affecting rate of flow into drains
• Soil permeability
• Depth of soil
• Drain spacing
• Drain opening
• Drain diameter
• Distribution of potential at a flow boundary

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Factors affecting erosion by water

• Climatic factors
• Soil characteristics
• Topography
• Vegetation
• Phases of erosion
• Detachment
• Transportation
• Deposition
• Types of soil movement by wind
• Suspension
• Saltation
• Surface creep

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Gully Erosion

• Aim of Gully Erosion Control
• To reduce peak flow rate
• To provide stable channel
• Runoff reduction
• Vegetative control
• Structures
• Stages of Gully Development
• Channel erosion by downward scour of topsoil
• Upstream movement of gully head
• Healing stage
• Stabilization of gully

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Terraces

• Terracing An erosion control method
• Types are
• Bench terrace
• Broad based terrace
• Functions of terraces
• To decrease length of hill-side slope
• To remove or retain runoff rate in area of
  inadequate rainfall
• Terrace Design involves
• Proper spacing
• Location of terraces
• Design of channel with suitable capacity
• Development of farmable cross-section
• Terrace Spacing Location
• Land slope
• Soil condition
• Proposed land use
• Farm roads

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Drainage and Reclamation

• Process and practice involved in bringing saline
  and alkali soils into productive condition
• Essentials of reclamation procedures
• Determine nature of the soil
• Degree of salinity or alkalinity
• Drainage Characteristics
• Topography of the land
• Presence of hardpan
• Reclamation Procedure
• Permanent reclamation
• Lowering water table (if high)
• Improving infiltration rate of soil
• Leaching of salts in saline soils
• Replacing excessive exchangeable Na by ca salts
• Suitable management practice
• Temporary reclamation
• Removing the salts crust from surface of soil
  (Biological)
• Ploughing salt surface-crust (Physical)

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Class projects

1. Design a channel of rectangular cross-section to
   carry water at the rate of 0.3m3/s a distance of
   5 km if the width is restricted to 1.5 m and the
   head loss along the length limited to 1 m.
   Consider lining to be of rough concrete (n
   0.015)
2. Determine the system capacity for a sprinkler
   irrigation system to irrigate 16ha of maize crop.
   Design moisture use rate is 5 mm/day. Moisture
   replaced in soil at each irrigation is 6 cm.
   Irrigation efficiency is 70. Irrigation period
   is 10 days in a 12-day interval. The system is
   to be operated for 20 hours per day.