Question

What is the field irrigation requirement (FIR)?

(a) The water required to meet the evaporation needs of a crop

(b) Amount of water required to delivered at the field to meet evapotranspiration and leaching needs

(c) Amount of water required to meet the net irrigation requirements plus water lost due to surface runoff and percolation

(d) Amount of water required to meet the field irrigation requirements plus water lost in conveyance through the canal system

I got this question during an interview.

Question is from Water Requirements of Crops in chapter Water Requirements of Crops of Irrigation Engineering

Answer 1

Right answer is (c) Amount of water required to meet the net irrigation requirements plus water lost due to surface runoff and percolation

To explain I would say: FIR can be defined as the water required meeting the net irrigation requirements plus the amount of water lost as surface runoff and through deep percolation.

Mathematically, FIR = NIR / Na where Na = application efficiency and NIR = Net irrigation requirement.