Irrigation efficiency is defined as the ratio of the amount of water available to the amount of water supplied from the reservoir. It is expressed in percentage.

Following are the different types of irrigation efficiency:

1. Efficiency of Water Conveyance

It is defined as the ratio of quantity of water delivered to the field to the quantity of water diverted to the canal from the reservoir. It may be symbolised by ηc. It can be obtained by the following expression:

            ηc = {W1/Wr} * 100

Where,

ηc = Water conveyance efficiency.

Wl = Amount of water available at the outlet’s point.

Wr = Amount of water supplied from the reservoir.

2. Efficiency of Water application

It is defined as the ratio of quantity of water stored in the root zone of the soil to the quantity of water delivered to the filed. It may be symbolised by ηa. It can be obtained by the following expression:

              ηa = {Wz/W1} * 100

Where,

ηa = Water application efficiency.

Wz = Amount of water stored in the root zone.

Wl = Amount of water supplied at the outlet point of the field.

3. Efficiency of Water use

It is defined as the quantity of water used beneficially including those of leaching requirement to the quantity of water delivered to the field. It may be expressed by ηu. It can be obtained by the following expression: ηu = {Wu/Wl} * 100

Where,

ηu = Water use efficiency.

Wu = Water used.

Wl = Water Applied.

4. Efficiency of Consumptive use

It can be defined as the ratio of normal consumptive use of water to the the net amount of water depleted from the root zone. It is expressed by ηcu. It can be obtained by the following expression: ηcu = {Cu/Wp} * 100

Where,

ηcu = Consumptive use efficiency.

Cu = Consumptive use of water.

Wp = Amount of water depleted from root zone.

5.Efficiency of Water Storage

It is defined as the ratio of quantity of water stored in the root zone of the soil to the quantity of water required to bring the moisture content of the soil to filed capacity. It is expressed by ηs.It can be obtained by the following expression:

                   ηs= {Wz/Wrz} * 100

Where, ηs = Storage efficiency.

Wz = Amount of water stored in the root zone.

Wrz= Root zone storage capacity.

6.Efficiency of Water Distribution

It is a measure of water distribution within the field. A low distribution efficiencymeans non-uniformity in the distribution of irrigation water. It is expressed by ηd. It can be obtained by the following expression:

                  ηd = {1-(Y/d)}*100.

Where,

Υ = Average numerical deviation in depth of water stored from average depthstored during irrigation.

d = Average depth of water stored during irrigation.