Question

Consumptive Irrigation Requirement is calculated using the following:

(i) Consumptive use

(ii) Effective rainfall

(iii) Water lost as percolation 

1. Only (i)
2. (i) and (ii)
3. (i) and (iii) 
4. (i), (ii) and (iii) 

Answer 1

Correct Answer - Option 2 : (i) and (ii)

Explanation

Consumptive use of water by a crop is the depth of water consumed by the plant in the process of transpiration and evaporation, during crop growth.

These two processes (i.e. transpiration and evaporation) collectively termed evapotranspiration.

Consumptive use of water by a crop is expressed as the depth of water per unit area for a specified period, such as days, months, or seasons. The value of consumptive use of water is needed to calculate the irrigation requirement of the crop.

We know,

a) Consumptive Irrigation Requirements (CIR) = Consumptive Use (Cu) – Effective Rainfall (Re)

b) Net Irrigation Requirement (NIR) = CIR + other requirements such as leaching

c) Field Irrigation Requirements (FIR) = NIR + Surface runoff losses + deep percolation losses

Or

\({\rm{FIR}} = \frac{{{\rm{NIR}}}}{{{\rm{Water\;application\;efficiency}}}}\)

d) Gross Irrigation Requirements (GIR) = FIR + Conveyance Losses (Seepage and Evaporation)

Or 

\({\rm{GIR}} = \frac{{{\rm{FIR}}}}{{{\rm{Water\;Conveyance\;efficiency}}}}\)

If you look through the above equations we can conclude that

 GIR > FIR, FIR > NIR, NIR > CIR 

∴ GIR > FIR > NIR > CIR