Irrigation Methods

Irrigation Methods are mainly classified into :

1. Surface Irrigation or Gravity Irrigation

2. Subsurface Irrigation or Sub-irrigation

3. Sprinkler or overhead irrigation

4. Drip or Trickle irrigation

SURFACE IRRIGATION Irrigation water flows across the field to the soil surface Primarily used for field crops and orchards Water is applied to the soil surface and the water flows

by gravity either through furrows, strips or basins. Water is applied from a channel located at the upper

reach of the field. Loss of water by conveyance and deep percolation is

high and the efficiency of irrigation is only 40-50% at field level in surface method of irrigation.

Properly constructed water distribution systems to give sufficient control of water to the fields

Effective land preparation to permit uniform distribution of water over the field are very important.

SURFACE IRRIGATION

Water is applied to the field in either the controlled or

uncontrolled manner.

Controlled: Water is applied from the head ditch and

guided by corrugations, furrows, borders, or ridges.

Uncontrolled: Wild flooding.

Surface irrigation is entirely practiced where water is

abundant.

Low initial cost of development is later offset by high

labor cost of applying water.

Deep percolation, runoff and drainage problems

Phases of Surface Irrigation

Phases of Surface Irrigation

1. Advance Phase:

When water is applied to the field, it advances across the surface until the water extends over the entire area. It may or may not directly wet the entire surface, but all of the flow paths have been completed.

Phases of Surface Irrigation

2. Wetting / Ponding Phase: Then the irrigation water either runs off the field or begins to pond on its surface. The interval between the end of the advance and when the inflow is cut off is called the wetting or ponding phase.

Phases of Surface Irrigation 3. Drainage Phase: The volume of water on the surface begins to decline after

the water is no longer being applied. It either drains from the surface (runoff) or infiltrates into the soil.

The drainage period is segregated into the depletion phase (vertical recession) and the recession phase (horizontal recession).

Phases of Surface Irrigation

a. Depletion: Depletion is the interval between cut off and the appearance of the first bare soil under the water.

b. Recession: Recession begins at that point and continues until the surface is drained.