Question

Determine the volume of water stored in unit area if unit weight of water is 9.8 KN/m^3, dry unit of soil is 17 KN/m^3, field capacity (F) is 2.35 m^2, and depth of root zone of the plant is 9 m.

(a) 36.69 m^3

(b) 36 m^3

(c) 36.12 m^3

(d) 36.25m^3

This question was addressed to me in a job interview.

I'd like to ask this question from Water Requirements of Crops in section Water Requirements of Crops of Irrigation Engineering

Answer 1

Right option is (a) 36.69 m^3

Easy explanation: We have field capacity (F) = (γw x volume of stored in unit area of soil / γd x d)

Therefore volume of stored water = (γd. d. F / γw)

= (17 x 9 x 2.35 / 9.8) (where, γw = unit weight of water, γd = dry unit weight of soil)

= 359.55 / 9.8

= 36.69 m^3.