Performance of farm irrigation.

• It is determined by the efficiency with which water is diverted, conveyed and applied.
• It is defined into following sections:

A. Irrigation efficiencies:

• Irrigation efficiency is defined as the ratio of percentage of irrigation farm/field/ project to the water diverted from the source of supply.
• When the water is measured at the farm head gate, it is “Farm irrigation efficiency”, and when measured at source of supply, it is called “overall efficiency”.
• It is expressed in % .
• It represents

a) % of volume of irrigation water transpired by plants

b) % of water evaporated from the soil

c) % water necessary to regulate the salt concentration in the soil solution and

d) % water used by plants in building plant tissue to the total volume of water diverted, stored or pumped from irrigation

Mathematically,

Ei=   (Wet +Wi- Re)/Wi x 100

Where,

Ei= irrigation efficiency %

Wet = The volume of irrigation water per unit area land transpired by plants, evaporated from soil during crop period.

Re = Effective rain fall

Wi = The volume of water per unit area of land that is stored in reservoir and diverted for irrigation.

B. Application uniformity:

• It describes how evenly an irrigation system distributes water to a field.
• Perfect uniformity means that the entire field receives an equal depth of water.
• Less than perfect uniformity implies that some field receives more water than the other areas.
• Highest uniformity can be expected on the fields with steep slope, low hydraulic roughness, low infiltration capacity of soil or when larger stream sizes are used.
• Application uniformity for drip irrigation is 90% and sprinkler irrigation is 70%.

C. Excessive irrigation:

• Leads to less aeration, nutrient loss and deep percolation.

D. Adequacy of irrigation:

• It is the percentage of field receiving efficient water to maintain the quantity of quality of crop production at a particular level.

E. Effectiveness of irrigation:

• It qualitatively describes the application efficiency, uniformity and adequacy of irrigation.
• Effectiveness of irrigation depends on:

1. Crop yield
2. Capital expenses
3. Maintenance expenses
4. Labor requirement
5. Mechanization of system
6. Energy expenses
7. Efficiencies