1. Free flooding:

• Ditches are excavated on field and water is allowed to flow across the field with no control mechanics.
• Suitable for irregular land.
• Inefficient method of irrigation.

 2. Border flooding:

• Land is divided into a number of strips with the help of low levees.
• Each strip has 10 to 20 meter width and 100 to 400 meter length.
• Supply of water is stopped once it reduce lower end.
• Suitable for close crops.

3. Check flooding:

• Similar to ordinary flooding except water is controlled with help of low and flat levees.
• Reduce percolation loss.

4. Basin Flooding:

• Special type of check flooding which is adopted specially for orchard tree.
• One or more tree are placed in basin and surface is flooded.

5. Furrow irrigation:

• Narrow ditches excavated between rows of plants and carry water through them.
• Spacing of furrow depends upon spacing of plants.

6. Sprinkler irrigation:

• Water is applied to soil in the form of spray through network of pipes and pumps.
• Suitable:
  • Topography is irregular.
  • Land gradient is steeper.
  • Crop water requirement is low.
  • Classified as:
  • Permanent system
  • Semi- permanent system
  • Portable system
• Advantage:
  • Seepage losses is completely eliminated.
  • Land levelling is not required.
  • No extra land required for ditches.
  • High efficiency.
• Disadvantage:
  • Affected by high wind.
  • Not suitable for crops with high water requirement.
  • Not suitable for high temperature area.

1.2 Hydraulics of irrigation distribution:

1. Advance phase:

• Time interval between the start of irrigation and arrival of the advancing (wetting) front at the lower end of the field.

2. Ponding phase:

• Irrigation time extending between the end of advance and inflow cut-off.

3. Depletion phase:

• Time interval between supply cutoff and the time that water dries up at the inlet boundary.

4. Recession phase:

• Time required for the water to recede from all points in the channel starting from the end of the depletion phase.

1.3 Efficiency irrigation method:

1. Efficiency of water conveyance:

• Ratio of water delivered into the field from the outlet point to the water entering into the channel at its starting point.

2. Efficiency of water application:

• Ratio of quantity of water stored into the roof zone of the crops to the quantity of water actually delivered into the field.

3. Efficiency of water storage:

• Ratio of quantity of water stored into the root zone during irrigation to the water needed in the root zone.

4. Efficiency of water use:

• Ratio of water beneficially used including leaching water to the quantity of water delivered.

5. Uniformity coefficient or water distribution efficiency:

• Represents the extent to which water has penetrated to a uniform depth throughout the field.

η = (1 – d/D)

where,

d = Average absolute value

D = Mean depth

1.4 Operation and management needs of surface and ground water irrigation schemes:

Operation of irrigation system:

• Operation of irrigation system is a package of organisational, economical and technical arrangement that ensure planned distribution and full use of water resource for heavy yield of agricultural crops of good quality under irrigation conditions.
• Operation measure includes:
  • Implementation of schedule water use practice to provide the irrigation regime required under specific meteorological condition on certain land areas under efficient water use.
  • Keeping irrigation, drain and other canal in working state by proper supervision and maintenance.
  • Prevention of excess water.
  • Control water loss of canal.
  • Organization of irrigation water accounting.

1.5 Canal operation plan:

• Method of organizing water delivery in a planned way by releasing, conveying and dividing water in canal system.
• It includes:
  • Starting and closure of season.
  • Starting storage.
  • Irrigation release schedule.
  • Responding to specific situation.

Data required for operation plan:

1. Water resource:

• Availability
• Storage status
• Inflow

2. Water demand:

• Cropping plan
• Rainfall

3. Canal status:

• Discharge
• Water level
• Losses

4. Irrigation schedule:

• Timing
• Duration

1.6 Participatory management:

• Participatory management is the participation of irrigation users in the management of irrigation system.
• Recognised all over world as tool of improving irrigation management along with sustainability of the system.

Objective participatory management:

• To promote and secure distribution of water among user and economic utilisation of water in agriculture.
• To protect environment and to ensure ecological balance inculcating sense of ownership of irrigation system.
• Users are directly involve in design process which will ensure better understanding of design and management of system.
• Farmers will have better idea of accounting, budgeting, planning and organizing techniques.
• Farmers can manage and operate the system more cheaply than government agencies.

References:

• WECS (1998), Design Guidelines for Surface Irrigation in Terai and Hills of Nepal, (Vol. I and II)
• Michael, A.M.(2011). Irrigation theory and practice
• FAO(1977). Guidelines for Predicting Crop Water Requirements. FAO Irrigation and Drainage Paper No. 24.

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